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AirCore samplers have been increasingly used to capture vertical profiles of trace gases reaching from the ground up to about 30 km, in order to validate remote sens- ing instruments and to investigate transport processes in the stratosphere. When deployed to a weather balloon, accu- rately attributing the trace gas measurements to the sampling altitudes is nontrivial, especially in the stratosphere. In this paper we present the CO-spiking experiment, which can be deployed to any AirCore on any platform in order to evalu- ate different computational altitude attribution processes and to experimentally derive the vertical resolution of the profile by injecting small volumes of signal gas at predefined GPS altitudes during sampling. We performed two CO-spiking flights with an AirCore from the Goethe University Frankfurt (GUF) deployed to a weather balloon in Traînou, France, in June 2019. The altitude retrieval based on an instantaneous pressure equilibrium assumption slightly overestimates the sampling altitudes, especially at the top of the profiles. For these two flights our altitude attribution is accurate within 250 m below 20 km. Above 20 km the positive bias becomes larger and reaches up to 1.2 km at 27 km altitude. Differences in descent velocities are shown to have a major impact on the altitude attribution bias. We parameterize the time lag between the theoretically attributed altitude and the actual CO-spike release altitude for both flights together and use it to empirically correct our AirCore altitude retrieval. Regard- ing the corrected profiles, the altitude attribution is accurate within ±120 m throughout the profile. Further investigations are needed in order to test for the scope of validity of this correction parameter regarding different ambient conditions and maximum flight altitudes. We derive the vertical resolu- tion from the CO spikes of both flights and compare it to the modeled vertical resolution. The modeled vertical resolution is too optimistic compared to the experimentally derived res- olution throughout the profile, albeit agreeing within 220 m. All our findings derived from the two CO-spiking flights are strictly bound to the GUF AirCore dimensions. The newly introduced CO-spiking experiment can be used to test differ- ent combinations of AirCore configurations and platforms in future studies.
Over recent decades, the global population has been rapidly increasing and human activities have altered terrestrial water fluxes to an unprecedented extent. The phenomenal growth of the human footprint has significantly modified hydrological processes in various ways (e.g. irrigation, artificial dams, and water diversion) and at various scales (from a watershed to the globe). During the early 1990s, awareness of the potential for increased water scarcity led to the first detailed global water resource assessments. Shortly thereafter, in order to analyse the human perturbation on terrestrial water resources, the first generation of large-scale hydrological models (LHMs) was produced. However, at this early stage few models considered the interaction between terrestrial water fluxes and human activities, including water use and reservoir regulation, and even fewer models distinguished water use from surface water and groundwater resources. Since the early 2000s, a growing number of LHMs have incorporated human impacts on the hydrological cycle, yet the representation of human activities in hydrological models remains challenging. In this paper we provide a synthesis of progress in the development and application of human impact modelling in LHMs. We highlight a number of key challenges and discuss possible improvements in order to better represent the human–water interface in hydrological models.
During this study clumped isotope analysis of carbonates was established at the Goethe University of Frankfurt, Germany. Therefore, preparation protocols and analytical parameters were elaborated to obtain precise and accurate Δ47 data. Briefly, analyte CO2 was cleaned cryogenically using glass extraction lines to remove traces of water that enable re-equilibration of C–O bonds in the gases. Furthermore, analyte CO2 was passed through a gas chromatograph (GC) to clean it from contaminants that produce isobaric interferences with m/z 47. Initially, phosphoric acid digestions of carbonates was conducted at 25 °C in McCrea-type reaction vessels. Afterwards samples were reacted at 90 °C using a common acid bath. Mass spectrometric analyses were performed using a MAT 253 equipped with a dual inlet system. Δ47 values were directly projected to the absolute scale using CO2 gases equilibrated at distinct temperatures.
In cooperation with Stefano Bernasconi and his research group at ETH Zurich we studied the non-linearity that occurs for the measurement of m/z 47. This effect results from secondary electrons created by the m/z 44 beam. These electrons cause a negative background on the m/z 47 collector. A correction procedure was proposed that relies on the determination of the negative background on the m/z 47 Faraday cup. This approach might reduce time-consuming analyses of heated gases which were used so far to account for the observed non-linearity. However, the suggested correction of the negative background on the m/z 47 cup is only applicable if the slit width of the m/z 44 beam is significantly wider than that of the m/z 47 beam.
This thesis, furthermore, presents a comparison of the different phosphoric acid digestion techniques which are commonly used for carbonate clumped isotope analysis. For calcitic and aragonitic material digested at 25 °C in McCrea-type vessels we observed that the sample size has an effect on Δ47 data: higher mean Δ47 values and a larger scatter of data were received for samples <7 mg than for larger aliquots. For carbonate samples digested at 90 °C in a common acid bath no sample size effect was determined. We assume that secondary re-equilibration of CO2 with water preferentially occurs at 25 °C producing the observed differences. However, a sample size effect can be avoided if reaction temperature is increased to 90 °C.
In order to make carbonate Δ47 data obtained from acid digestions at 90 °C comparable to Δ47 data received from reactions at 25 °C the difference of the acid fractionation factores (Δ47*25-90) between both temperatures has to be known. For the determination of the Δ47*25-90 value we have considered Δ47 data made at 25 °C from samples >7 mg only. For calicte and aragonite we obtained differences in fractionation factores of 0.075‰ and 0.066‰, respectively. These Δ47*25-90 values are coincident with the theoretical prediction of 0.069‰ proposed for calcite (Guo et al., 2009).
Moreover, this dissertation comprises a calibration study of the clumped isotope thermometer based on various natural calcites that grew between 9 and 38 °C. The samples include a brachiopod shell, a bivalve shell, an eggshell of an ostrich and foraminifera tests which formed from distinct biomineralizing processes. Furthermore we included an authigenic carbonate crystallized from biological-induced precipitation. The following linear relationship between 1/T2 and Δ47 was determined (with Δ47 in ‰ and T in K):
Δ47 = 0.0327 (± 0.0026) x 106 / T2 + 0.3030 (± 0.0308) (R2 = 0.9915)
This equation differs from the pioneering Ghosh et al. (2006a) calibration. However, our regression line is statistically indistinguishable from that of Henkes et al. (2013) which is based on aragonitic mollusks and calcitic brachiopod shells. Both studies have in common that calibration data were, at first, directly referenced to the absolute scale. In addition, both datasets rely on similar digestion techniques. Furthermore, the two calibrations are conform with the theoretical prediction of Guo et al. (2009).
The calcite calibration of the clumped isotope paleothermometer received in this study was applied to Δ47 data measured for Silurian brachiopods shells from Gotland/Sweden. Prior to isotopic analysis the fossils were intensively investigated for their preservation state (CL, SEM, trace elements). The lowest T(Δ47) values of ca. 28 to 33 °C were estimated from ultrastructurally well-preserved regions of some shells. For these samples also the lowest δ18Ow values of Silurian seawater were determined. These estimates of ca. −1‰ confirm the assumption that the δ18O value of the Silurian ocean was buffered to (0 ± 1)‰.
Nevertheless, most studied shells were characterized by a patchwork of pristine and altered shell portions resulting in elevated T(Δ47) values which plot mostly between 40 and 60 °C. Our results indicate that the clumped isotopic composition of the shells were altered at low water-rock ratios, not affecting the δ18O values. Δ47 and δ18O data of associated diagenetic phases (sparitic and micritic phases of the inner fillings of the fossils) provide evidence that the sparitic cements grew during several diagenetic events which occurred at different temperatures in fluid-buffered systems. We, furthermore, conclude that the micritic phases lithified at a very early diagenetic stage with the δ18O values being most probably close to a Silurian seawater composition
Der am Südrande des Harzes existierende etwa 100 km lange Ausstrich von Zechsteinschichten bietet mit seinen Gipsen, Anhydriten und Dolomiten gute Voraussetzungen zur Entstehung einer Karstlandschaft. Er erstreckt sich von Badenhausen im Landkreis Osterode über den Landkreis Nordhausen bis hin nach Pölsfeld im Landkreis Sangerhausen.
Motivated by the question of whether and how wave–wave interactions should be implemented into atmospheric gravity-wave parametrizations, the modulation of triadic gravity-wave interactions by a slowly varying and vertically sheared mean flow is considered for a non-rotating Boussinesq fluid with constant stratification. An analysis using a multiple-scale WKBJ (Wentzel–Kramers–Brillouin–Jeffreys) expansion identifies two distinct scaling regimes, a linear off-resonance regime, and a nonlinear near-resonance regime. Simplifying the near-resonance interaction equations allows for the construction of a parametrization for the triadic energy exchange which has been implemented into a one-dimensional WKBJ ray-tracing code. Theory and numerical implementation are validated for test cases where two wave trains generate a third wave train while spectrally passing through resonance. In various settings, of interacting vertical wavenumbers, mean-flow shear, and initial wave amplitudes, the WKBJ simulations are generally in good agreement with wave-resolving simulations. Both stronger mean-flow shear and smaller wave amplitudes suppress the energy exchange among a resonantly interacting triad. Experiments with mean-flow shear as strong as in the vicinity of atmospheric jets suggest that internal gravity-wave dynamics are dominated in such regions by wave modulation. However, triadic gravity-wave interactions are likely to be relevant in weakly sheared regions of the atmosphere.
This thesis deals with the analysis of “presolar” silicates and oxides by high resolution mass spectrometry and electron microscopy techniques. This “stardust” was identified by its extreme oxygen isotopic anomalies, which point to nucleosynthetic reactions in stellar interiors, in the carbonaceous chondrite Acfer 094. Isotopic, chemical and mineralogical studies on these stardust grains therefore allow the testing of astrophysical questions on Earth, which are otherwise only accessible by spectroscopy and theoretical models. The class of presolar silicates has been identified only six years ago in 2002, although it was known already from spectroscopic observations that silicates represent the most abundant type of dust in the galaxy. The development of the “NanoSIMS” was a crucial step in this respect, because this ion probe with its superior spatial resolution of only 50 nm allowed the detection of the typically 300 nm sized presolar silicates. A total of 142 presolar silicates and 20 presolar oxides were identified within Acfer 094, whose matrix therefore contains 163 ± 14 ppm presolar silicates and 26 ± 6 ppm presolar oxides. This is among the highest amounts reported so far for any primitive solar system material. The majority of detected stardust grains derive from asymptotic giant branch stars of 1 – 2.5 Msun and close-to-solar or slightly lower-than-solar metallicity. However, by measuring the Si isotopic compositions of some enigmatic grains, it could be shown that there is a sub-class of presolar silicates characterized by an extreme enrichment of 17O and a moderate enhancement of 30Si relative to solar, whose origins might be explained by formation in binary stellar systems. About 10% of all grains exhibit an enrichment in 18O and some of them also of 28Si relative to solar, which most likely point to an origin in type II supernova explosions. The Si isotopic measurements also allowed to quantify the effect of the s-process on the Si isotopes in low-mass asymptotic giant branch stars. The results agree well with theoretical predictions. The grains were furthermore characterized by SEM and the chemistries of about half of the grains were determined by Auger electron spectroscopy. The majority of grain morphologies are consistent with what is expected from condensation experiments. However, a lot of grains are altered by Fe-rich minerals, which are either of primary condensation or of secondary ISM or solar nebula origin. Furthermore, complex presolar grains consisting of refractory Al-rich grains attached to silicate material could be identified, which have been predicted by condensation theory and observational evidence. Nine presolar silicates were analyzed by combined NanoSIMS/TEM studies. The majority of grains are Mg-rich and amorphous, which is in contrast to astrophysical evidence, which mainly postulate crystalline Mg-rich and amorphous Fe-rich circumstellar condensates. However, the grains might have been rendered amorphous by secondary processes in the ISM or could have condensed under non-equilibrium, low-temperature conditions in the circumstellar outflow. The grains are more likely characterized by a variable, pyroxene-like chemistry, which could be a result of sputtering in the ISM, which preferentially removes Mg. The detected crystalline presolar silicates in this study and in other work are all olivines, whereas grains with a pyroxene stoichiometry are all amorphous except one. This supports astrophysical models which point to different formation pathways for these two types of grains and therefore different crystallinity. However, the relatively high Fe content of three detected presolar olivines in this study and in other work is in contrast to astrophysical evidence and theoretical considerations, which predict essentially Fe-free crystalline grains. It is therefore possible that the infrared spectra might also be compatible with less Mg-rich olivines. The only crystalline presolar silicate with a pyroxene-like stoichiometry is the unusual grain 1_07: although it is chemically enstatite, the electron diffraction pattern could only be indexed to silicate perovskite, which is stable above ~23 GPa. The discovery of a high-pressure phase of presolar origin shows that dust grains encountering interstellar shocks might not necessarily be completely destroyed. In astrophysical models it is in principle also possible that a fraction of larger grains might survive such a shock wave encounter as a high-pressure modification, which is supported by this discovery.
Numerical simulation of flow, H₂SO₄ cycle and new particle formation in the CERN CLOUD chamber
(2011)
To study the effect of galactic cosmic rays on aerosols and clouds, the Cosmic Leaving OUtdoor Droplets (CLOUD) project was established. Experiments are carried out at a 26 m3 tank at CERN (Switzerland). In the experiments, the effect of ionising particle radiation on H2SO4 particle formation and growth is investigated. To evaluate the experimental configuration, the experiment was simulated using a coupled multidimensional CFD – particle model (CLOUD-FPM). In the model the coupled fields of gas/vapour species, temperature, flow velocity and particle properties were computed to investigate the tank's mixing state and mixing times. Simulation results show that the mixing state of the tank's contents largely depends on the characteristics of the mixing fans and a 1-fan configuration, as used in first experiments, may not be sufficient to ensure a homogeneously mixed chamber. To mix the tank properly, 2 fans are necessary. The 1/e response times for instantaneous changes of wall temperature and saturation ratio inside the chamber were found to be in the order of few minutes. Particle nucleation and growth was also simulated and particle number size distribution properties of the freshly nucleated particles (particle number, mean size, standard deviation of the assumed log-normal distribution) were found to be mixed over the tank's volume similar to the gas species.
To study the effect of galactic cosmic rays on aerosols and clouds, the Cosmics Leaving OUtdoor Droplets (CLOUD) project was established. Experiments are carried out at a 26.1 m3 tank at CERN (Switzerland). In the experiments, the effect of ionizing radiation on H2SO4 particle formation and growth is investigated. To evaluate the experimental configuration, the experiment was simulated using a coupled multidimensional computational fluid dynamics (CFD) – particle model. In the model the coupled fields of gas/vapor species, temperature, flow velocity and particle properties were computed to investigate mixing state and mixing times of the CLOUD tank's contents. Simulation results show that a 1-fan configuration, as used in first experiments, may not be sufficient to ensure a homogeneously mixed chamber. To mix the tank properly, two fans and sufficiently high fan speeds are necessary. The 1/e response times for instantaneous changes of wall temperature and saturation ratio were found to be in the order of few minutes. Particle nucleation and growth was also simulated and particle number size distribution properties of the freshly nucleated particles (particle number, mean size, standard deviation of the assumed log-normal distribution) were found to be distributed over the tank's volume similar to the gas species.
Central and western Europe were affected by a compressional tectonic event in the Late Cretaceous, caused by the convergence of Iberia and Europe. Basement uplifts, inverted graben structures, and newly formed marginal troughs are the main expressions of crustal shortening. Although the maximum activity occurred during a short period of time between 90 and 75 Ma, the exact timing of this event is still unclear. Dating of the start and end of Late Cretaceous basin inversion gives very different results depending on the method applied. On the basis of borehole data, facies, and thickness maps, the timing of basin reorganization was reconstructed for several basins in central Europe. The obtained data point to a synchronous start of basin inversion at 95 Ma (Cenomanian), 5 Myr earlier than commonly assumed. The end of the Late Cretaceous compressional event is difficult to pinpoint in central Europe, because regional uplift and salt migration disturb the signal of shifting marginal troughs. Late Campanian to Paleogene strata deposited unconformably on inverted structures indicate slowly declining uplift rates during the latest Cretaceous. The differentiation of separate Paleogene inversion phases in central Europe does not appear possible at present.
Central Europe was affected by a compressional tectonic event in the Late Cretaceous, caused by the convergence of Iberia and Europe. Basement uplifts, inverted graben structures and newly formed marginal troughs are the main expressions of crustal shortening. Although the maximum activity occurred in a short period between 90 and 75 Ma, the exact timing of this event is still unclear. Dating of start and end of basin inversion is very different depending on the applied method. On the basis of borehole data, facies and thickness maps, the timing of basin re-organisation was reconstructed for several basins in Central Europe. The obtained data point to a synchronous start of basin inversion already at 95 Ma (Cenomanian), 5 Million years earlier than commonly assumed. The end of the Late Cretaceous compressional event is more difficult to pinpoint, because regional uplift and salt migration disturb the signal of shifting marginal troughs. Unconformities of Late Campanian to Paleogene age on inverted structures indicate slowly declining uplift rates.
Chlorine monoxide (ClO) plays a key role in stratospheric ozone loss processes at midlatitudes. We present two balloonborne in situ measurements of ClO conducted in northern hemisphere midlatitudes during the period of the maximum of total inorganic chlorine loading in the atmosphere. Both ClO measurements were conducted on board the TRIPLE balloon payload, launched in November 1996 in Le´on, Spain, and in May 1999 in Aire sur l’Adour, France. For both flights a ClO daylight and night time vertical profile could be derived over an altitude range of approximately 15–31 km. ClO mixing ratios are compared to model simulations performed with the photochemical box model version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). Simulations along 24-h backward trajectories were performed to study the diurnal variation of ClO in the midlatitude lower stratosphere. Model simulations for the flight launched in Aire sur l’Adour 1999 show a good agreement with the ClO measurements. For the flight launched in Le´on 1996, a similar good agreement is found, except at around ~ 650 K potential temperature (~26km altitude). However, a tendency is found that for solar zenith angles greater than 86°–87° the simulated ClO mixing ratios substantially overestimate measured ClO by approximately a factor of 2.5 or more for both flights. Therefore we conclude that no indication can be deduced from the presented ClO measurements that substantial uncertainties exist in midlatitude chlorine chemistry of the stratosphere. An exception is the situation at solar zenith angles greater than 86°–87° where model simulations substantial overestimate ClO observations.
Chlorine monoxide (ClO) plays a key role in stratospheric ozone loss processes at midlatitudes. We present two balloon-borne in situ measurements of ClO conducted in northern hemisphere midlatitudes during the period of the maximum of total inorganic chlorine loading in the atmosphere. Both ClO measurements were conducted on board the TRIPLE balloon payload, launched in November 1996 in León, Spain, and in May 1999 in Aire sur l'Adour, France. For both flights a ClO daylight and night-time vertical profile was derived over an altitude range of approximately 15-35 km. ClO mixing ratios are compared to model simulations performed with the photochemical box model version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). Simulations along 24-hour backward trajectories were performed to study the diurnal variation of ClO in the midlatitude lower stratosphere. Model simulations for the flight launched in Aire sur l'Adour 1999 show an excellent agreement with the ClO measurements. For the flight launched in León 1996, an overall good agreement is found, whereas the flight is characterized by a more complex dynamical situation due to a possible mixture of vortex and non-vortex air. We note that for both flights at solar zenith angles greater than 86°-87° simulated ClO mixing ratios are higher than observed ClO mixing ratios. However, the present findings indicate that no substantial uncertainties exist in midlatitude chlorine chemistry of the stratosphere.
Modelling short-term variability in carbon and water exchange in a temperate Scots pine forest
(2015)
The vegetation–atmosphere carbon and water exchange at one particular site can strongly vary from year to year, and understanding this interannual variability in carbon and water exchange (IAVcw) is a critical factor in projecting future ecosystem changes. However, the mechanisms driving this IAVcw are not well understood. We used data on carbon and water fluxes from a multi-year eddy covariance study (1997–2009) in a Dutch Scots pine forest and forced a process-based ecosystem model (Lund–Potsdam–Jena General Ecosystem Simulator; LPJ-GUESS) with local data to, firstly, test whether the model can explain IAVcw and seasonal carbon and water exchange from direct environmental factors only. Initial model runs showed low correlations with estimated annual gross primary productivity (GPP) and annual actual evapotranspiration (AET), while monthly and daily fluxes showed high correlations. The model underestimated GPP and AET during winter and drought events. Secondly, we adapted the temperature inhibition function of photosynthesis to account for the observation that at this particular site, trees continue to assimilate at very low atmospheric temperatures (up to daily averages of −10 °C), resulting in a net carbon sink in winter. While we were able to improve daily and monthly simulations during winter by lowering the modelled minimum temperature threshold for photosynthesis, this did not increase explained IAVcw at the site. Thirdly, we implemented three alternative hypotheses concerning water uptake by plants in order to test which one best corresponds with the data. In particular, we analyse the effects during the 2003 heatwave. These simulations revealed a strong sensitivity of the modelled fluxes during dry and warm conditions, but no single formulation was consistently superior in reproducing the data for all timescales and the overall model–data match for IAVcw could not be improved. Most probably access to deep soil water leads to higher AET and GPP simulated during the heatwave of 2003. We conclude that photosynthesis at lower temperatures than assumed in most models can be important for winter carbon and water fluxes in pine forests. Furthermore, details of the model representations of water uptake, which are often overlooked, need further attention, and deep water access should be treated explicitly.
Modelling short-term variability in carbon and water exchange in a temperate Scots pine forest
(2015)
The vegetation–atmosphere carbon and water exchange at one particular site can strongly vary from year to year, and understanding this interannual variability in carbon and water exchange (IAVcw) is a critical factor in projecting future ecosystem changes. However, the mechanisms driving this IAVcw are not well understood. We used data on carbon and water fluxes from a multi-year eddy covariance study (1997–2009) in a Dutch Scots pine forest and forced a process-based ecosystem model (Lund–Potsdam–Jena General Ecosystem Simulator; LPJ-GUESS) with local data to, firstly, test whether the model can explain IAVcw and seasonal carbon and water exchange from direct environmental factors only. Initial model runs showed low correlations with estimated annual gross primary productivity (GPP) and annual actual evapotranspiration (AET), while monthly and daily fluxes showed high correlations. The model underestimated GPP and AET during winter and drought events. Secondly, we adapted the temperature inhibition function of photosynthesis to account for the observation that at this particular site, trees continue to assimilate at very low atmospheric temperatures (up to daily averages of −10 °C), resulting in a net carbon sink in winter. While we were able to improve daily and monthly simulations during winter by lowering the modelled minimum temperature threshold for photosynthesis, this did not increase explained IAVcw at the site. Thirdly, we implemented three alternative hypotheses concerning water uptake by plants in order to test which one best corresponds with the data. In particular, we analyse the effects during the 2003 heatwave. These simulations revealed a strong sensitivity of the modelled fluxes during dry and warm conditions, but no single formulation was consistently superior in reproducing the data for all timescales and the overall model–data match for IAVcw could not be improved. Most probably access to deep soil water leads to higher AET and GPP simulated during the heatwave of 2003. We conclude that photosynthesis at lower temperatures than assumed in most models can be important for winter carbon and water fluxes in pine forests. Furthermore, details of the model representations of water uptake, which are often overlooked, need further attention, and deep water access should be treated explicitly.
Analysing the composition of ambient ultrafine particles (UFPs) is a challenging task due to the low mass and chemical complexity of small particles, yet it is a prerequisite for the identification of particle sources and the assessment of potential health risks. Here, we show the molecular characterization of UFPs, based on cascade impactor (Nano-MOUDI) samples that were collected at an air quality monitoring station near one of Europe's largest airports, in Frankfurt, Germany. At this station, particle-size-distribution measurements show an enhanced number concentration of particles smaller than 50 nm during airport operating hours. We sampled the lower UFP fraction (0.010–0.018, 0.018–0.032, 0.032–0.056 µm) when the air masses arrived from the airport. We developed an optimized filter extraction procedure using ultra-high-performance liquid chromatography (UHPLC) for compound separation and a heated electrospray ionization (HESI) source with an Orbitrap high-resolution mass spectrometer (HRMS) as a detector for organic compounds. A non-target screening detected ∼200 organic compounds in the UFP fraction with sample-to-blank ratios larger than 5. We identified the largest signals as homologous series of pentaerythritol esters (PEEs) and trimethylolpropane esters (TMPEs), which are base stocks of aircraft lubrication oils. We unambiguously attribute the majority of detected compounds to jet engine lubrication oils by matching retention times, high-resolution and accurate mass measurements, and comparing tandem mass spectrometry (MS2) fragmentation patterns between both ambient samples and commercially available jet oils. For each UFP stage, we created molecular fingerprints to visualize the complex chemical composition of the organic fraction and their average carbon oxidation state. These graphs underline the presence of the homologous series of PEEs and TMPEs and the appearance of jet oil additives (e.g. tricresyl phosphate, TCP). Targeted screening of TCP confirmed the absence of the harmful tri-ortho isomer, while we identified a thermal transformation product of TMPE-based lubrication oil (trimethylolpropane phosphate, TMP-P). Even though a quantitative determination of the identified compounds is limited, the presented method enables the qualitative detection of molecular markers for jet engine lubricants in UFPs and thus strongly improves the source apportionment of UFPs near airports.
Analysing the composition of ambient ultrafine particles (UFP) is a challenging task due to the low mass and chemical complexity of small particles, yet it is a prerequisite for the identification ofparticle sources and the assessment of potential health risks. Here, we show the molecular characterization of UFP, based on cascade impactor (Nano-MOUDI) 10samples that were collected at an air quality monitoring station nearby one of Europe`s largest airports in Frankfurt, Germany. At this station, particle-size-distribution measurements show enhanced number concentration of particles smaller than 50nm during airport operating hours. We sampled the lower UFP fraction (0.010-0.018 μm; 0.018-0.032 μm; 0.032-0.056 μm) when the air masses arrived from the airport. We developed an optimized filter extraction procedure, used ultra-high performance liquid chromatography (UHPLC) for compound separation, and a heated electrospray ionization (HESI) source with an 15Orbitrap high-resolution mass spectrometer (HRMS) as a detector for organic compounds. A non-target screening detected ~200 organic compounds in the UFP fraction with sample-to-blank ratios larger than five. We identified the largest signals as homologous series of pentaerythritol esters (PEE) and trimethylolpropane esters (TMPE), which are base stocks of aircraft lubrication oils. We unambiguously attribute the majority of detected compounds to jet engine lubrication oils by matching retention times, high-resolution/accurate mass (HR/AM) measurements, and comparing MS/MS fragmentation patterns between both ambient samples and commercially available jet oils. For each UFP stage, we created molecular fingerprints to visualize the complex chemical composition ofthe organic fraction and their average carbon oxidation state. These graphs underline the presence of the homologous series of PEE and TMPE, and the appearance of jet oil additives (e.g. tricresyl phosphate (TCP)). Targeted screening on TCP confirmed the absence of the harmful tri-orthoisomer, while we identified a thermal transformation product of TMPE-based lubrication oil (trimethylolpropane phosphate (TMP-P)). Even though a quantitative determination of the identified compounds is limited, the presented method enables the qualitative detection of molecular markers for jet engine lubricants in UFP and thus strongly improves the source apportionment of UFP near airports.
As part of two drilling campaigns of the International Continental Scientific Drilling Program (ICDP), several geophysical borehole measurements were carried out by the Leibniz Institute for Applied Geophysics (LIAG) in two lakes. The acquired data was used to answer stratigraphic and paleoclimatic research questions, including the establishment of robust age-depth models and the construction of continuous lithological profiles.
Lake Towuti is located on Sulawesi (Indonesia), within the "Indo-Pacific Warm Pool" (IPWP), a globally important region for atmospheric heat and moisture budgets. The lake exists for approximately one million years, but its exact age is uncertain. We present the first agedepth model for the approximately 100 m continuous sediment sequence from the central part of the lake. The basis for this model is the magnetic susceptibility measured in the borehole and a tephra layer with an age of about 797 ka at 72 m depth. Our age-depth model is inferred from cyclostratigraphic analysis of borehole data and covers a period from 903 ± 11 to 131 ± 67 ka. We suggest that orbital eccentricity and/or changes between global cold and warm periods are responsible for hydroclimatic changes in the IPWP, that these changes affect sedimentation processes in Lake Towuti, and that we can measure and observe this effect in the sediment properties today. Additionally, we created a continuous artificial lithological profile from a series of different borehole data using cluster analysis. This provides information from parts of the borehole where no sediment is available due to core loss.
Lake Ohrid is 1.36 million years old and is located on the Balkan Peninsula on the border between Albania and North Macedonia. The primary hole 'DEEP' in the central part of the lake has been the subject of several investigations, but information about sediments of the marginal locations 'Pestani' and 'Cerava' have not been published yet. In our study, we use natural gamma radiation (GR) measured in the borehole to generate an age-depth model for DEEP. This is performed using the correlation of GR to the global LR04 reference record of Lisiecki and Raymo (2005).
The age information is then transferred via prominent seismic marker horizons to the other two sites, Pestani and Cerava, where it provides the first age-control points for the construction of age-depth models from correlation of GR to LR04. The generated age-depth models are tested using cyclostratigraphic methods, but the limits of this approach are revealed. At DEEP, sedimentation rates (SR) from the cyclostratigraphic method and the correlative approach differ by 2.8 %, at Pestani this difference is 16.7 %, and at Cerava the quality of the data does not allow a reliable evaluation of SR using the cyclostratigraphic approach. We used cluster analysis to construct artificial lithological profiles at all three sites and integrated them into the respective age-depth models. This enables us to determine which sediment types were deposited at what time, and we recognize the change between warm and cold periods in the sediment properties at all three locations. The analyses in this study were all performed on borehole and seismic data and thus do not involve sediment core data. Especially at Pestani and Cerava, new insights into the sedimentological history of Lake Ohrid could be obtained.
In the last part we discuss the occurrence of the half-precession (HP) signal in the European region during the last one million years. The focus is on Lake Ohrid, but a range of other proxies, from the eastern Mediterranean, across the European continent, up to Greenland are analyzed in regards to HP. Applying filters, we focus on the frequency range with a period of 13-8.5 ka and only HP remains in the records. We use correlative methods to determine the clarity of the HP signal in proxies distributed across the European realm. Additionally, we determined the development of HP over time. The HP signal is clearest in the southeast and decreases toward the north. It is further more pronounced in interglacial periods and in the younger part (<621 ka) of most proxies. We suggest that there are mechanisms that transmit the HP signal from its origin near the equator to higher latitudes via different processes. In this context, for instance, the African monsoon, the Nile River and the Mediterranean outflow via the Strait of Gibraltar can be important factors.
Over the last several decades, spinel-structured minerals with the chemical formula AB2O4 (where A and B stand for divalent and trivalent cations, respectively) have attracted more and more attention, particularly with regards to their breakdown at high pressures and temperatures and the nature of the so-called "post-spinel" phases. Spinel-structured phases with different endmember compositions, like magnetite (Fe3O4), hercynite (FeAl2O4) or spinel (MgAl2O4), are known to breakdown differently at high pressure-temperature conditions (e.g., Akaogi et al. 1999; Schollenbruch et al. 2010; Woodland et al. 2012). Such phases are of particular interest when they incorporate ferric (Fe3+) and ferrous (Fe2+) cations as this makes their stability sensitive to redox conditions. Since magnetite and magnesioferrite (MgFe3+ 2O4) have been found as inclusions in diamond (e.g., Stachel et al. 1998; Harte et al. 1999; Wirth et al. 2014; Palot et al. 2016; Jacob et al. 2016), understanding their phase relations is important for setting constraints on the conditions of their formation.
This study aimed to experimentally investigate the phase relations of Fe-Mg spinel-structured phases at conditions of the deep upper mantle and transition zone. Exploring the stability of new post-spinel phases and their characterization were also major goals of this study. Approaching a pyrolitic mantle composition by adding amounts of SiO2 in the system allowed constraints on the relevance of Fe-Mg post-spinel phases coexisting with mantle silicates to be made. ...
Long-term average groundwater recharge representing the sustainable groundwater resources is modeled as a 0.5° by 0.5° grid on global scale by the WaterGAP Global Hydrology Model. Due to uncertainties of estimating groundwater recharge, especially in semiarid and arid regions, independent estimates are used for calibrating the model. This work compiled a new set of independent groundwater recharge estimates based on a work of Scanlon et al. (2006). The 59 independent estimates, together with an already existing independent estimates compilation, are used for the evaluation of two WGHM variants; one variant is modeling with an improved more realistically distributed daily precipitation dataset.
The objective of this thesis is the evaluation of the modeled data of the WaterGAP Global Hydrology Model (WGHM). The analysis of the impact of the new Watch Forcing Data (WFD) precipitation dataset on the modeled groundwater recharge tends to result in lower values in humid and higher values in (semi-)arid regions compared to the WGHM standard variant. Comparing both WGHM variants to the independent estimates compilations, representing (semi-)arid regions, the WGHM variant shows over- and underestimations especially of the low values and the WGHM WFD variant shows a bias toward overestimation especially for values below 4 mm/yr. The analysis of texture, hydrogeology and vegetation/ land cover could not give satisfying explanations for the discrepancies, but derived from the groundwater recharge measurement methods analysis indirect/ localized recharge seems to be a significant factor causing underestimations, as resulted in the comparison of the independent estimates based on Scanlon et al. 2006 with the WGHM variants.
Derivation and characterization of a new filter for nonlinear high-dimensional data assimilation
(2015)
Data assimilation (DA) combines model forecasts with real-world observations to achieve an optimal estimate of the state of a dynamical system. The quality of predictions in nonlinear and chaotic systems such as atmospheric or oceanic circulation is strongly sensitive to the initial conditions. Therefore, beyond the consistent reconstruction of past states, a primary relevance of advanced DA methods concerns the proper model initialization. The ensemble Kalman filter (EnKF) and its deterministic variants, mostly square root filters such as the ensemble transform Kalman filter (ETKF), represent a popular alternative to variational DA schemes. They are applied in a wide range of research and operations. Their forecast step employs an ensemble integration that fully respects the nonlinear nature of the analyzed system. In the analysis step, they implicitly assume the prior state and observation errors to be Gaussian. Consequently, in nonlinear systems, the mean and covariance of the analysis ensemble are biased and these filters remain suboptimal. In contrast, the fully nonlinear, non-Gaussian particle filter (PF) relies on Bayes' theorem without further assumptions, which guarantees an exact asymptotic behavior. However, it is exposed to weight collapse, particularly in higher-dimensional settings, known as the curse of dimensionality.
This work presents a new method to obtain an analysis ensemble with mean and covariance that exactly match the corresponding Bayesian estimates. This is achieved by a deterministic matrix square root transformation of the forecast ensemble, and subsequently a suitable random rotation that significantly contributes to filter stability while preserving the required second-order statistics. The forecast step remains as in the ETKF. The algorithm, which is fairly easy to implement and computationally efficient, is referred to as the nonlinear ensemble transform filter (NETF). The limitation with respect to fully-nonlinear filtering is that the NETF only considers the mean and covariance of the Bayesian analysis density, neglecting higher-order moments.
The properties and performance of the proposed algorithm are investigated via a set of experiments. The results indicate that such a filter formulation can increase the analysis quality, even for relatively small ensemble sizes, compared to other ensemble filters in nonlinear, non-Gaussian scenarios. They also confirm that localization enhances the applicability of this PF-inspired scheme in larger-dimensional systems. Finally, the novel filter is coupled to a large-scale ocean general circulation model with a realistic observation scenario. The NETF remains stable with a small ensemble size and shows a consistent behavior. Additionally, its analyses exhibit low estimation errors, as revealed by a comparison with a free ensemble integration and the ETKF. The results confirm that, in principle, the filter can be applied successfully and as simple as the ETKF in high-dimensional problems. No further modifications are needed, even though the algorithm is only based on the particle weights. Thus, it is able to overcome the curse of dimensionality, even in deterministic systems. This proves that the NETF constitutes a promising and user-friendly method for nonlinear high-dimensional DA.
Das Klima, insbesondere der Niederschlag ist einer der wichtigsten natürlichen Gestaltungsfaktoren für die Savannenregion Westafrikas. Morphodynamik, Bodenbildung, Abflußregime sowie Wasserhaushalt werden direkt vom Klima bestimmt. Der Niederschlag ist zudem das begrenzende Element für das Wachstum von Flora und Fauna. Jede Änderung der Niederschlagsmenge hat gravierende Folgen für die Landschaft und seine Bewohner. Die Untersuchung langfristiger klimatischer Veränderungen ist ein Beitrag die Entstehung und den Wandel der Landschaft zu verstehen. Hierdurch können parallele Entwicklungen zwischen Natur- und Kulturraum im langfristigen Zusammenhängen gesehen werden. Ziel ist, das Klima des Tschadseegebietes seit dem Beginn regelmäßiger Aufzeichnung von Klimadaten mit Hilfe verschiedener statistischer Verfahren zu beschreiben. Des weiteren sollen Wechselwirkungen und Zusammenhänge zu externen Faktoren (Globale Zirkulation, Ozeantemperatur, Solarstrahlung,...) aufgezeigt werden.
Über gewundene Bergkrystalle
(1894)
About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday1. Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres2,3. In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles4, thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth5,6, leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer7,8,9,10. Although recent studies11,12,13 predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon2, and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Köhler theory)2,14, has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown15 that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10−4.5 micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10−4.5 to 10−0.5 micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
Für eine möglichst vollständige analytische Beschreibung werden in der statistischen Klimatologie beobachtete Klimazeitreihen als Realisation eines stochastischen Prozesses, das heißt als eine Folge von Zufallsvariablen verstanden. Die Zeitreihe soll im wesentlichen durch eine analytische Funktion der Zeit beschrieben werden können und die Beobachtung nur durch Zufallseinflüsse von dieser Funktion abweichen. Diese analytische Funktion setzt sich aus der Summe zeitlich strukturierter Komponenten zusammen, welche aus klimatologischem Blickwinkel interpretierbar erscheinen. Es werden Funktionen zugelassen, die den Jahresgang, Trends, episodische Komponenten und deren Änderung beschreiben. Die Extremereignisse sind als eine besondere weitere Komponente in die Zeitreihenanalyse aufgenommen und als von Änderungen in den Parametern der Verteilung unabhängige, extreme Werte definiert. Die Zufallseinflüsse sollen zunächst als Realisierungen unabhängiger normalverteilter Zufallsvariablen mit dem Erwartungswert Null und im Zeitablauf konstanter Varianz interpretiert werden können. In diesem Fall beschreibt die analytische Funktion der Zeit, die Summe detektierter strukturierter Komponenten, den zeitlichen Verlauf des Mittels. Ein zu einem bestimmten Zeitpunkt tatsächlich beobachteter Wert kann dann als eine mögliche Realisation einer Zufallsvariablen interpretiert werden, die der Gaußverteilung mit dem Mittelwert µ(t) zur Zeit t und konstanter Varianz genügt. Da die zugrundeliegenden Annahmen, unter Verwendung klimatologisch interpretierbarer Basisfunktionen, in der Analyse von Klimazeitreihen, die nicht die Temperatur betreffen, zumeist nicht erfüllt sind, wird in eine Verallgemeinerung des Konzepts der Zeitreihenzerlegung in einen deterministischen und einen statistischen Anteil eingeführt. Zeitlich strukturierte Änderungen werden nun in verschiedenen Verteilungsparametern frei wählbarer Wahrscheinlichkeitsdichtefunktionen gesucht. Die gängige Beschränkung auf die Schätzung einer zeitlich veränderlichen Lokation wird aufgehoben. Skalenschätzer sowie Schätzer fär den Formparameter spielen ebenso relevante Rollen fär die Beschreibung beobachteter Klimavariabilität. Die Klimazeitreihen werden wieder als Realisation eines Zufallprozesses verstanden, jedoch genügen die Zufallsvariablen nun einer frei wählbaren Wahrscheinlichkeitsdichtefunktion. Die zeitlich strukturierten Änderungen in den Verteilungsparametern werden auf Basis der gesamten Zeitreihe für jeden Zeitpunkt geschätzt. Die aus der Analyse resultierende analytische Beschreibung in Form einer zeitabhängigen Wahrscheinlichkeitsdichtefunktion ermöglicht weiterhin die Schätzung von Über- und Unterschreitungswahrscheinlichkeiten beliebig wählbarer Schwellenwerte für jeden Zeitpunkt des Beobachtungszeitraums. Diese Methode erlaubt insbesondere eine statistische Modellierung monatlicher Niederschlagsreihen durch die Zerlegung in einen deterministischen und einen statistischen Anteil. In dem speziellen Fall von 132 Reihen monatlicher Niederschlagssummen deutscher Stationen 1901-2000 gelingt eine vollständige analytische Beschreibung der Reihen durch ihre Interpretation als Realisation einer Gumbel-verteilten Zufallsvariablen mit variablem Lage- und Streuparameter. Auf Basis der gewonnenen analytischen Beschreibung der Reihen kann beispielsweise im Westen Deutschlands auf Verschiebungen der jährlichen Überschreitungsmaxima des 95%-Perzentils von den Sommer- in die Wintermonate geschlossen werden. Sie werden durch relativ starke Anstiege in der Überschreitungswahrscheinlichkeit (bis 10%) in den Wintermonaten und nur geringe Zunahmen oder aber Abnahmen in den Sommermonaten hervorgerufen. Dies geht mit einer Zunahme der Unterschreitungswahrscheinlichkeit in den Winter- und einer Abnahme in den Sommermonaten einher. Monte-Carlo-Simulationen zeigen, daß jahreszeitlich differenzierte Schätzungen von Änderungen im Erwartungswert, also gebräuchliche Trends, auf Basis der Kleinst-Quadrate-Methode systematischen Bias und hohe Varianz aufweisen. Eine Schätzung der Trends im Mittel auf Basis der statistischen Modellierung ist somit ebenso den Kleinst-Quadrate-Schätzern vorzuziehen. Hinsichtlich der Niederschlagsanalysen stellen jedoch aride Gebiete, mit sehr seltenen Niederschlägen zu bestimmten Jahreszeiten, die Grenze der Methode dar, denn zu diesen Zeitpunkten ist eine vertrauenswürdige Schätzung einer Wahrscheinlichkeitsdichtefunktion nicht möglich. In solchen Fällen ist eine grundsätzlich andere Herangehensweise zur Modellierung der Reihen erforderlich.
Für eine möglichst vollständige analytische Beschreibung werden in der statistischen Klimatologie beobachtete Klimazeitreihen als Realisation eines stochastischen Prozesses, das heißt als eine Folge von Zufallsvariablen verstanden. Die Zeitreihe soll im wesentlichen durch eine analytische Funktion der Zeit beschrieben werden können und die Beobachtung nur durch Zufallseinflüsse von dieser Funktion abweichen. Diese analytische Funktion setzt sich aus der Summe zeitlich strukturierter Komponenten zusammen, welche aus klimatologischem Blickwinkel interpretierbar erscheinen. Es werden Funktionen zugelassen, die den Jahresgang, Trends, episodische Komponenten und deren Änderung beschreiben. Die Extremereignisse sind als eine besondere weitere Komponente in die Zeitreihenanalyse aufgenommen und als von Änderungen in den Parametern der Verteilung unabhängige, extreme Werte definiert. Die Zufallseinflüsse sollen zunächst als Realisierungen unabhängiger normalverteilter Zufallsvariablen mit dem Erwartungswert Null und im Zeitablauf konstanter Varianz interpretiert werden können. In diesem Fall beschreibt die analytische Funktion der Zeit, die Summe detektierter strukturierter Komponenten, den zeitlichen Verlauf des Mittels. Ein zu einem bestimmten Zeitpunkt tatsächlich beobachteter Wert kann dann als eine mögliche Realisation einer Zufallsvariablen interpretiert werden, die der Gaußverteilung mit dem Mittelwert µ(t) zur Zeit t und konstanter Varianz genügt. Da die zugrundeliegenden Annahmen, unter Verwendung klimatologisch interpretierbarer Basisfunktionen, in der Analyse von Klimazeitreihen, die nicht die Temperatur betreffen, zumeist nicht erfüllt sind, wird in eine Verallgemeinerung des Konzepts der Zeitreihenzerlegung in einen deterministischen und einen statistischen Anteil eingeführt. Zeitlich strukturierte Änderungen werden nun in verschiedenen Verteilungsparametern frei wählbarer Wahrscheinlichkeitsdichtefunktionen gesucht. Die gängige Beschränkung auf die Schätzung einer zeitlich veränderlichen Lokation wird aufgehoben. Skalenschätzer sowie Schätzer fär den Formparameter spielen ebenso relevante Rollen fär die Beschreibung beobachteter Klimavariabilität. Die Klimazeitreihen werden wieder als Realisation eines Zufallprozesses verstanden, jedoch genügen die Zufallsvariablen nun einer frei wählbaren Wahrscheinlichkeitsdichtefunktion. Die zeitlich strukturierten Änderungen in den Verteilungsparametern werden auf Basis der gesamten Zeitreihe für jeden Zeitpunkt geschätzt. Die aus der Analyse resultierende analytische Beschreibung in Form einer zeitabhängigen Wahrscheinlichkeitsdichtefunktion ermöglicht weiterhin die Schätzung von Über- und Unterschreitungswahrscheinlichkeiten beliebig wählbarer Schwellenwerte für jeden Zeitpunkt des Beobachtungszeitraums. Diese Methode erlaubt insbesondere eine statistische Modellierung monatlicher Niederschlagsreihen durch die Zerlegung in einen deterministischen und einen statistischen Anteil. In dem speziellen Fall von 132 Reihen monatlicher Niederschlagssummen deutscher Stationen 1901-2000 gelingt eine vollständige analytische Beschreibung der Reihen durch ihre Interpretation als Realisation einer Gumbel-verteilten Zufallsvariablen mit variablem Lage- und Streuparameter. Auf Basis der gewonnenen analytischen Beschreibung der Reihen kann beispielsweise im Westen Deutschlands auf Verschiebungen der jährlichen Überschreitungsmaxima des 95%-Perzentils von den Sommer- in die Wintermonate geschlossen werden. Sie werden durch relativ starke Anstiege in der Überschreitungswahrscheinlichkeit (bis 10%) in den Wintermonaten und nur geringe Zunahmen oder aber Abnahmen in den Sommermonaten hervorgerufen. Dies geht mit einer Zunahme der Unterschreitungswahrscheinlichkeit in den Winter- und einer Abnahme in den Sommermonaten einher. Monte-Carlo-Simulationen zeigen, daß jahreszeitlich differenzierte Schätzungen von Änderungen im Erwartungswert, also gebräuchliche Trends, auf Basis der Kleinst-Quadrate-Methode systematischen Bias und hohe Varianz aufweisen. Eine Schätzung der Trends im Mittel auf Basis der statistischen Modellierung ist somit ebenso den Kleinst-Quadrate-Schätzern vorzuziehen. Hinsichtlich der Niederschlagsanalysen stellen jedoch aride Gebiete, mit sehr seltenen Niederschlägen zu bestimmten Jahreszeiten, die Grenze der Methode dar, denn zu diesen Zeitpunkten ist eine vertrauenswürdige Schätzung einer Wahrscheinlichkeitsdichtefunktion nicht möglich. In solchen Fällen ist eine grundsätzlich andere Herangehensweise zur Modellierung der Reihen erforderlich.
Die konventionelle Extremwertstatistik die sich an der Über- bzw. Unterschreitungshäufigkeit bestimmter Schwellenwerte orientiert, beinhaltet den Nachteil, daß Änderungen der Parameter der Häufigkeitsverteilung die Extremwertwahrscheinlichkeit beeinflussen. So kann allein das Vorhandensein eines Trends für derartige Veränderungen verantwortlich sein. Die hier gewählte Methodik vermeidet diesen Nachteil, indem sie eine Zerlegung der betrachteten Zeitreihen in einen strukturierten und einen unstrukturierten Anteil durchführt. Dabei setzt sich der strukturierte Anteil aus einer Trend-, Saison- und glatten Komponente zusammen. Aus der Summe dieser in der Zeitreihe signifikant enthaltenen Komponenten läßt sich die Eintrittswahrscheinlichkeit von Extremwerten ableiten. Ähnliches gilt für den unstrukturierten Anteil insbesondere für die Varianz des Residuums. Das Residuum kann aber auch Werte enthalten, die nicht zu ihrer ansonsten angepaßten Häufigkeitsverteilung passen. Solche Werte werden als Extremereignisse bezeichnet und sind von den Extremwerten zu unterschieden. In der vorliegenden Arbeit werden nun, getrennt voneinander, durch Änderungen in den Parametern der Häufigkeitsverteilung hervorgerufene Variationen der Extremwertwahrscheinlichkeit als auch parameterunabhängige Extremereignisse der bodennahen Lufttemperatur betrachtet. Als Datenbasis dienten 41, wahrscheinlich homogene, europäische Stationszeitreihen von Monatsmitteltemperaturen, die den Zeitraum von 1871 bis 1990 abdecken. In den untersuchten Temperaturzeitreihen wurde an 37 von 41 Stationen ein positiver Trend detektiert, woraus ein Anstieg der Extremwertwahrscheinlichkeit mit der Zeit resultiert. Die glatten, niederfrequenten Schwingungen wirken sich in den meisten Fällen um 1890 und 1975 negativ und um 1871, 1940 und 1990 positiv auf die Extremwertwahrscheinlich keit aus. Desweiteren treten Änderungen in der Saisonfigur bezüglich der Amplitude und der Phasenlage auf. Detektierte Zunahmen in der Amplitude des Jahresgangs führen zu einer positiven Änderung der Extremwertwahrscheinlichkeit. Signifikante Änderungen in der Phasenlage der Saisonfigur erzeugen in den Anomaliezeitreihen einen saisonal unterschiedlichen Trend, dessen Amplitude, in den betrachteten Fällen, in der Größenordnung der Trendkomponente liegt. Saisonal unterschiedliche Trends beeinflussen saisonal unterschiedlich die Wahrscheinlichkeit für das Eintreten von Extremwerten. Die Residuen von fünf Temperaturzeitreihen weisen signifikante Varianzinstationaritäten auf, wobei in nur einem Fall die Varianz mit der Zeit zunimmt und somit einen Anstieg der Extremwertwahrscheinlichkeit erzeugt. Extremereignisse treten vorwiegend in Form besonders kalter Winter auf und können wahrscheinlich als Realisation eines Poisson-Prozesses interpretiert werden. Sie erscheinen zufällig über den Beobachtungszeitraum verteilt mit einer mittleren Wiederkehrzeit von mehr als 10 Jahren.
Ecophysiological studies on Antarctic cryptophytes to assess whether climatic changes such as ocean acidification and enhanced stratification affect their growth in Antarctic coastal waters in the future are lacking so far. This is the first study that investigated the combined effects of increasing availability of pCO2 (400 and 1000 µatm) and irradiance (20, 200 and 500 μmol photons m−2 s −1) on growth, elemental composition and photophysiology of the Antarctic cryptophyte Geminigera cryophila. Under ambient pCO2, this species was characterized by a pronounced sensitivity to increasing irradiance with complete growth inhibition at the highest light intensity. Interestingly, when grown under high pCO2 this negative light effect vanished and it reached highest rates of growth and particulate organic carbon production at the highest irradiance compared to the other tested experimental conditions. Our results for G. cryophila reveal beneficial effects of ocean acidification in conjunction with enhanced irradiance on growth and photosynthesis. Hence, cryptophytes such as G. cryophila may be potential winners of climate change, potentially thriving better in more stratified and acidic coastal waters and contributing in higher abundance to future phytoplankton assemblages of coastal Antarctic waters.
Reliable identification of chondrules, calcium-aluminum-rich inclusions (CAIs), carbonate grains, and Ca-phosphate grains at depth within untouched, unprepared chondritic samples by a nondestructive analytical method, such as synchrotron X-ray fluorescence (SXRF) computed tomography (CT), is an essential first step before intrusive analytical and sample preparation methods are performed. The detection of a local Ca-enrichment could indicate the presence of such a component, all of which contain Ca as major element and/or Ca-bearing minerals, allowing it to be precisely located at depth within a sample. However, the depth limitation from which Ca-K fluorescence can travel through a chondrite sample (e.g., ∼115 µm through material of 1.5 g cm−3) to XRF detectors leaves many Ca-bearing components undetected at deeper depths. In comparison, Sr-K lines travel much greater distances (∼1700 µm) through the same sample density and are, thus, detected from much greater depths. Here, we demonstrate a clear, positive, and preferential correlation between Ca and Sr and conclude that Sr-detection can be used as proxy for the presence of Ca (and, thus, Ca-bearing components) throughout mm-sized samples of carbonaceous chondritic material. This has valuable implications, especially for sample return missions from carbonaceous C-type asteroids, such as Ryugu or Bennu. Reliable localization, identification, and targeted analysis by SXRF of Ca-bearing chondrules, CAIs, and carbonates at depth within untouched, unprepared samples in the initial stages of a multianalysis investigation insures the valuable information they hold of pre- and post-accretion processes in the early solar system is neither corrupted nor destroyed in subsequent processing and analyses.
Chemical ozone loss in winter 1991–1992 is recalculated based on observations of the HALOE satellite instrument, ER-2 aircraft measurements and balloon data. HALOE satellite observations are shown to be reliable in the lower stratosphere below 400 K, at altitudes where profiles are most likely disturbed by the enhanced sulfate aerosols, as a result of the Mt. Pinatubo eruption in June 1991. Very large chemical ozone loss was observed below 400 K from Kiruna balloon observations between December and March 1992. Additionally, for the two winters after the Mt. Pinatubo eruption, HALOE satellite observations show a stronger extent of chemical ozone loss at lower altitudes compared to other Arctic winter between 1991 and 2003. In stipe of already occurring deactivation of chlorine in March 1992, Mipas-B and LPMA balloon observations indicate still chlorine activation at lower altitudes, consistent with observed chemical ozone loss occurring between February and March and April. Enhanced chemical ozone loss in the Arctic winter 1991–1992 as calculated in earlier studies is corroborated here.
Chemical ozone loss in winter 1991–1992 is recalculated based on observations of the HALOE satellite instrument, Version 19, ER-2 aircraft measurements and balloon data. HALOE satellite observations are shown to be reliable in the lower stratosphere below 400 K, at altitudes where the measurements are most likely disturbed by the enhanced sulfate aerosol loading, as a result of the Mt.~Pinatubo eruption in June 1991. Significant chemical ozone loss (13–17 DU) is observed below 380 K from Kiruna balloon observations and HALOE satellite data between December 1991 and March 1992. For the two winters after the Mt. Pinatubo eruption, HALOE satellite observations show a stronger extent of chemical ozone loss towards lower altitudes compared to other Arctic winters between 1991 and 2003. In spite of already occurring deactivation of chlorine in March 1992, MIPAS-B and LPMA balloon observations indicate that chlorine was still activated at lower altitudes, consistent with observed chemical ozone loss occurring between February and March and April. Large chemical ozone loss of more than 70 DU in the Arctic winter 1991–1992 as calculated in earlier studies is corroborated here.
In dieser Arbeit wurde der chemische Ozonverlust in der arktischen Stratosphäre über elf Jahre hinweg, zwischen 1991 und 2002, mit Hilfe der so genannten "Ozon-Tracer Korrelationstechnik" (TRAC), untersucht. Bei dieser Methode werden Korrelationen zwischen Ozon und langlebigen Spurenstoffen im Verlauf des Winters im Polarwirbels beobachtet und so der jährliche akkumulierte Ozonverlust berechnet. Die Ergebnisse dieser Arbeit basieren im wesentlichen auf Messdaten der Satelliteninstrumente: HALOE (Halogen Occultation Experiment) auf UARS (Upper Atmosphere Research Satellite) und ILAS (Improved Limb Atmospheric Spectrometer) Instrument auf ADEOS (Advanced Earth Observing Satellite). Das HALOE Instrument misst seit Oktober 1991 kontinuierlich alle zwei bis drei Monate für einige Tage in höheren nördlichen Breiten. ILAS lieferte ausschließlich für den Winter 1996-97 Messungen, die über sieben Monate hinweg in hohen Breiten aufgenommen wurden. Aufgrund der eingeführten Erweiterungen und Verbesserungen der Methode in dieser Arbeit, konnte die Methode anhand einer detaillierten Studie für den Winter 1996-97 validiert werden. Die ILAS Messreihe wurde dazu verwendet, erstmals die Untersuchung der zeitlichen Entwicklung von Ozon-Tracer Korrelationen kontinuierlich für die gesamte Lebensdauer des Polarwirbels durchzuführen. Dabei wurden auch Korrelationen während der Bildung des Wirbels untersucht und im Besonderen mögliche Mischungsvorgänge zwischen Wirbelluft und Luftmassen außerhalb des Wirbels. Ausserdem wurde ein Vergleich der Ergebnisse von ILAS und HALOE Messdaten durchgeführt und Unterschiede in den Ergebnissen tiefgreifend analysiert. Basierend auf HALOE Messungen konnte die erweiterte TRAC Methode über elf Jahren hinweg angewendet werden. Damit war erstmals eine konsistente Analyse von Ozonverlust und Chloraktivierung über diesen Zeitraum möglich. Die Erweiterungen führten zu einer Verringerung und genauen Quantifizierung von Unsicherheiten der Ergebnisse. Ein deutlicher Zusammenhang zwischen meteorologischen Bedingungen, Chloraktivierung und dem chemischen Ozonverlust wurde deutlich. Weiterhin zeigte sich eine Abhängigkeit zwischen den meteorologischen Bedingungen und der Homogenität des Ozonverlustes innerhalb eines Winters, sowie der mögliche Einfluss von horizontaler Mischung auf Luftmassen in einem schwach ausgeprägten Polarwirbel. In dieser Arbeit wurde eine positive Korrelation zwischen den über die gesamte Lebensdauer des Wirbels auftretenden möglichen PSC-Flächen und den akkumulierten Ozonverlusten für die elf untersuchten Jahre deutlich. Es konnte darüber hinaus gezeigt werden, dass der Ozonverlust von deutlich mehr Einflüssen als nur von der Fläche möglichen PSC Auftretens bestimmt wird, sondern zum Beispiel von der Stärke der Sonneneinstrahlung abhängt. Außerdem lassen sich Auswirkungen von Vulkanausbrüchen, wie zum Beispiel im Jahr 1991 der des Mount Pinatubo, identifizieren.
Barriereinseln und Außensände, geformt durch eine Kombination aus Wind, Wellen, Strömung und Küstenlängstransport gelten als morphologisch hoch aktive Küstenbereiche und variieren häufig in Ursprung, Genese und Entwicklung. Sie besitzen durch ihre dissipative Wirkungsweise eine bedeutende Schutzfunktion für rückwärtige Inseln, Halligen und Festlandbereiche und bilden vor der Küste Nordfrieslands die westliche Außengrenze des Wattenmeeres.
Ziel der nachfolgenden Studie ist es, anhand hochauflösender Georadarmessungen und sedimentologischer Daten aus Bohrungen die Landschaftsgeschichte an der Westküste Amrums sowie die Entstehung und interne sedimentäre Architektur des der Insel westlich angelagerten Kniepsandes zu untersuchen und die Prozesse, die zur Genese geführt haben, durch Datierungen zeitlich einzuordnen. Auf Grundlage der gewonnenen Daten wurden zwei stratigraphische Modelle entwickelt, welche die geologisch-geomorphologischen Prozesse und Sedimentationsbedingungen im Westküstenvorfeld erklären.
Ein Modell zeigt die Landschaftsentwicklung an der Westküste Amrums und beschreibt die Sedimentationsbedingungen, die im Vorfeld der Westküste herrschten, bevor der Kniepsand an die Insel heranwanderte. Auf der Landoberfläche des ertrinkenden saaleeiszeitlichen Geestkerns wurden zu Beginn der Flandrischen Transgression feinkörnige Sedimente eines Mischund Schlickwatts abgelagert. Es ist davon auszugehen, dass der damals noch weit vor der Küste Amrums liegende Kniepsand eine Barriere bildete und so an der heute hochenergetischen Westküste für strömungsberuhigte Sedimentationsbedingungen sorgte. Durch Erosion am Geestkern bildeten sich in unterschiedlichen Höhenpositionen fossile Kliffs, die dem damaligen Meeresspiegelstand entsprechen.
Ein weiteres Modell beschreibt den Andockmechanismus des Kniepsandes an die Insel Amrum. Durch die Anlagerung des ehemaligen Außensandes und den damit einhergehenden Sedimentinput wurden die Bedingungen für eine großflächige Dünenbildung geschaffen.
Barriereinseln und Nehrungshaken, geformt durch eine Kombination aus Wind, Wellen, Strömung und Küstenlängstransport gelten als geologisch junge und morphologisch hoch aktive Küstenbereiche und variieren häufig in Ursprung, Genese und Entwicklung. Bisherige Untersuchungen zur Stratigraphie dieser durch engräumige Fazieswechsel geprägten Sedimentationsräume basieren häufig allein auf Bohrungen. Daher sind die interne sedimentologische Struktur und die Prozesse, die zur Entwicklung von Barriereinseln und Nehrungshaken geführt haben, oftmals unzureichend untersucht.
Ziel der folgenden Studie war es, anhand hochauflösender Georadarmessungen (GPR) und Bohrungen die Entstehung und interne sedimentäre Architektur der Nehrungshaken von Sylt und Amrum zu rekonstruieren. Durch die Korrelation von Sediment- und Radarfazies konnten über den bisherigen Kenntnisstand hinaus wertvolle, sich ergänzende Informationen zur Geologie des oberflächennahen Untergrundes der Inseln Sylt und Amrum gewonnen werden. Auf dieser Grundlage wurden für den Süden Sylts, die Westküste von Amrum und den Norden Amrums stratigraphische Modelle entwickelt, die schematisch den sedimentologischen Aufbau, die geomorphologisch-geologische Genese und die am Aufbau beteiligten Prozesse zusammenfassen. Die Einordnung in einen absoluten Zeitrahmen wurde durch Datierungen (AMS Radiokohlenstoff-Methode, Aminosäure-Racemisierungs-Methode) ermöglicht.
Die Ergebnisse sind als Beispiel für die Heterogenität und Individualität von Nehrungshaken und Barriereinseln zu sehen. Es konnte gezeigt werden, dass Nehrungshaken hinsichtlich ihres Aufbaus, ihrer sedimentären Struktur sowie den Prozessen ihrer Entstehung sehr unterschiedlich sind.
Mit Ausnahme der heutigen Dünen zeigt die Stratigraphie der Ansatzzone des südlichen Nehrungshakens von Sylt an den zentralen Inselgeestkern südlich der Ortschaft Rantum insgesamt eine Vergröberungs-Sequenz von tonigem Mischwatt im Liegenden über Sandwatt bis zu den gröberen washover-Schichten im Hangenden. Eine Besonderheit und regionale Abweichung stellt die Stratigraphie bei Puan Klent/Thörnhörn dar. Dort wurde im Liegenden der Watt-Fazies ein fossiler Strandhaken nachgewiesen.
Die transgressive Sequenz der Ansatzzone des südlichen Nehrungshakens von Sylt bei Rantum auf Sylt ist kennzeichnend für eine landwärts gerichtete Wanderungsbewegung der Inselbarriere unter steigendem Meeresspiegel. Das Resultat des als „barrier rollover“ bezeichneten morphologischen Prozesses ist die allmähliche Erosion der westlichen Barrierefront. Das erodierte Sediment der Westküste wurde entweder durch overwash-Prozesse im rückwärtigen Inselbereich als washover fan abgelagert oder gelangte in den Küstenlängstransport, wurde zur Inselspitze transportiert und dort akkumuliert. Diese führte allmählich zum Wachstum und zur Progradation der südlichen Inselspitze (Hörnum Odde) in die sich südlich anschließende Tiderinne des Hörnum-Tiefs. Zahlreiche Erosionsdiskordanzen unterhalb des heutigen Meeresspiegels markieren ursprüngliche Inselspitzenendpositionen (time lines) und sind auf hochenergetische Sturmflutereignisse zurückzuführen. Die time lines werden nach Süden hin jünger und zeichnen unterschiedliche Stadien der Progradation nach, die ein episodisches Wachstum der Inselspitze in Abhängigkeit von der Sedimentverfügbarkeit und der Sturmflutintensität belegen. Alte Erosionsdiskordanzen belegen die frühe submarine Genese der Hörnum Odde. Ein starkes Wachstum der südlichen Inselspitze Sylts lässt sich im Mittelalter nachweisen.
Sturmfluten führten zudem immer wieder zu overwash-Prozessen und Überschwemmungen der noch jungen Inselspitze. Dies belegen ältere washover-Ablagerungen, die in unterschiedlichen Phasen der Nehrungshakenentwicklung nachgewiesen werden konnten. Rezente overwash-Prozesse sind auf die heutigen Dünen beschränkt und wurden in dieser Arbeit mit der Fragestellung untersucht, ob und inwieweit das Georadar als Methode zur Prospektion von washover-Sedimenten herangezogen werden kann.
Die unmittelbare Nachbarschaft der beiden Nehrungshaken von Sylt und Amrum lässt einen ähnlichen sedimentären Aufbau, eine analoge Genese in einem einheitlichen Prozess-System sowie ein vergleichbares Alter vermuten. Durch die Untersuchungen im Norden von Amrum sollte festgestellt werden, in wie weit das für die Hörnum Odde nachgewiesene Zusammenspiel von Küstenlängstransport, Progradation, sturmflutbedingten overwash-Prozessen und die zeitliche Unterbrechung des Längenwachstums durch Sturmfluterosion auch für Amrum zutrifft. Entgegen der Erwartungen unterscheidet sich der nördliche Nehrungshaken der Insel Amrum signifikant vom südlichen Nehrungshaken der Nachbarinsel Sylt.
Studien zur Landschaftsentwicklung an der Westküste Amrums wurden in einem Modell zusammengefasst, dass die Sedimentationsbedingungen, die im Westküstenvorfeld herrschten bevor der Kniepsand an die Insel heranwanderte, beschreibt. Auf der Landoberfläche des ertrinkenden saaleeiszeitlichen Geestkerns wurden zu Beginn der Flandrischen Transgression feinkörnige Sedimente eines Misch- und Schlickwatts abgelagert. Es ist davon auszugehen, dass der damals noch weit vor der Küste Amrums liegende Kniepsand eine Barriere bildete und so an der heute hochenergetischen Westküste für strömungsberuhigte Sedimentationsbedingungen sorgte. Ein weiteres Modell beschreibt den Andockmechanismus des Kniepsandes an die Insel Amrum. Durch die Anlagerung des ehemaligen Außensandes und den damit einhergehenden Sedimentinput wurden die Bedingungen für eine großflächige Dünenbildung geschaffen.
Die vorliegende Arbeit stellt einen Ansatz zur Systematisierung der Konzeption und Entwicklung webbasierter multimedialer Lehr-/Lernobjekte (mmL-Objekte) in der Physischen Geographie, im Wesentlichen in der Teildisziplin Geomorphologie, vor. Auf allgemeine Ausführungen zu mediendidaktischen Grundlagen und Begrifflichkeiten im Zusammenhang internetgestützter Lehr-/Lernszenarien folgt die Darstellung von Strategien der Wissensstrukturierung, Wissensaneignung und fachwissenschaftlicher Methodik im Lehr-/Lernkontext geomorphologischer Prozesse und ihrer Modellierung im Internet. Die Aufbereitung des Prozesskomplexes Bodenerosion seht im Mittelpunkt. Ein Überblick über Potentiale computergestützter Modellierung und Visualisierung zur Entwicklung webbasierter multimedialer Lehr-/Lernmaterialien in der Geographie leitet über zur Erarbeitung eines präskriptiven Ansatzes zur Konzeption interaktiver Lernaufgaben. Sie setzen sich zusammen aus einer Visualisierungskomponente, den Möglichkeiten zur Interaktion mit der Visualisierung und mindestens einer Aufgabenstellung. Vor allem in computerunterstützten Lehr-/Lernprozessen, die selbständiges Lernen erfordern, erweisen sie sich als wesentliches didaktisches Element, um sicherzustellen, dass sich Lernende aktiv und nicht nur rezeptiv mit Inhalten und Medien in der für erfolgreiche Lernprozesse erforderlichen Intensität auseinander setzen. Ausgehend von der Funktion des zu entwickelnden Lehr-/Lernangebotes und dem jeweiligen angestrebten Zielhorizont eines Lehr-/Lernelements werden Empfehlungen zur Konstruktion aufgabenorientierter mmL-Objekte vorgeschlagen. Exemplarisch wird die praktische Anwendung theoretisch begründeter Empfehlungen anhand von aufgabenorientierten mmL-Objekten (interaktiven Lernaufgaben) aufgezeigt und diskutiert, die im Rahmen des BMBF-Projektes „WEBGEO – Webbing von Geoprozessen für die Grundausbildung Physische Geographie“ und im Rahmen der Lehrveranstaltung „Erstellung von E-Learning-Modulen durch Studierende“ entwickelt wurden.
This study presents a comprehensive and critical assessment of the meteorological conditions and atmospheric flow during the Lagrangian-type "Hill Cap Cloud Thuringia 2010" experiment (HCCT-2010). HCCT-2010 was performed in September and October 2010 at Mt. Schmücke in the Thuringian forest, Germany, applying three measurements sites (upwind, in-cloud, downwind) to study physical and chemical aerosol-cloud-interactions. A Lagrangian-type hill cap cloud experiment requires suitable cloud and particularly connected airflow conditions, i.e. representative air masses at the different measurement sites. Therefore, the present study aimed at the identification of time periods during the 6-weeks duration of the campaign, where such conditions were fulfilled and which can be used in further data examinations.
The following topics were studied in detail: (i) the general synoptic weather situations including the mesoscale flow conditions by means of a classification of advected air masses and calculation of non-dimensional flow parameters (e.g. Froude number), (ii) local meteorological conditions, including synoptic front passages, the presence of orographic or frontal cloudiness, cloud base heights and vertical stratification, and (iii) local flow conditions by means of statistical analyses using the quasi-inert trace gas ozone and selected size bins of particle number size distributions as well as SF6 tracer experiments in the campaign area. A comprehensive analyses using statistical measures such as the COD (Coefficient Of Divergence) and cross-correlation have been carried out for the first time in the context of a Lagrangian-type hill cap cloud experiment. Suitable criteria for the aimed statistical analyses were thus developed and applied in the present study to characterise the local flow connectivity in detail.
The comprehensive examination resulted in a total of 14 so-called "Full Cloud Events" (FCE), which are shown to conform to the Lagrange-type experimental philosophy of HCCT-2010. In addition, 15 so-called "Non-Cloud Events" (NCEs) could be established, which can be used as reference cases as they provide similarly suitable flow conditions but no cloud at the summit site. Orographic cloudiness was identified for approx. one third of the FCE periods, while about two thirds were associated to synoptic fronts. The statistical flow analyses indicate the existence of a strong link between the sites during the events, particularly under constant south-westerly flow conditions, high wind speeds and slightly stable stratification. The COD analyses using continuously measured concentrations of ozone and the 49 nm diameter particle bin revealed particularly for COD values below 0.1 very consistent time series, i.e. closely linked air masses between the different sites. The cross-correlation analysis revealed under connected flow conditions typical overflow times of about 15 to 30 min between the two valley sites. Additionally, the performed SF6 tracer experiments during the campaign clearly demonstrate that under appropriate meteorological conditions a Lagrangian-type approach is valid and that the connected flow validation procedure developed in this work is suitable for identifying such conditions. Finally, an overall evaluation of the identified FCEs is presented, which provides the basis for subsequent investigations of the measured chemical and physical data during HCCT-2010.
The Altenberg–Teplice Volcanic Complex (ATVC) is a large ~ NNW–SSE trending volcano-plutonic system in the southern part of the Eastern Erzgebirge (northern Bohemian Massif, south-eastern Germany and northern Czech Republic). This study presents high precision U–Pb CA-ID-TIMS zircon ages for the pre-caldera volcano-sedimentary Schönfeld–Altenberg Complex and various rocks of the caldera stage: the Teplice rhyolite, the microgranite ring dyke, and the Sayda-Berggießhübel dyke swarm. These data revealed a prolonged time gap of ca. 7–8 Myr between the pre-caldera stage (Schönfeld–Altenberg Complex) and the climactic caldera stage. The volcanic rocks of the Schönfeld–Altenberg Complex represent the earliest volcanic activity in the Erzgebirge and central Europe at ca. 322 Ma. The subsequent Teplice rhyolite was formed during a relatively short time interval of only 1–2 Myr (314–313 Ma). During the same time interval (314–313 Ma), the microgranite ring dyke intruded at the rim of the caldera structure. In addition, one dyke of the Sayda-Berggiesshübel dyke swarm was dated at ca. 314 Ma, while another yielded a younger age (ca. 311 Ma). These data confirm the close genetic and temporal relationship of the Teplice rhyolite, the microgranite ring dyke, and (at least part of) the Sayda-Berggießhübel dyke swarm. Remarkably, the caldera formation in the south of the Eastern Erzgebirge (caldera stage of ATVC: 314–313 Ma) and that in the north (Tharandt Forest caldera: 314–312 Ma) occurred during the same time. These data document a large ~ 60 km NNW–SSE trending magmatic system in the whole Eastern Erzgebirge. For the first time, Hf-O-isotope zircon data was acquired on the ring dyke from the ATVC rocks to better characterize its possible sources. The homogeneous Hf-O-isotope zircon data from the microgranite ring dyke require preceding homogenization of basement rocks. Some small-scale melts that were produced during Variscan amphibolite-facies metamorphism show similar Hf-O-isotope characteristics and can therefore be considered as the most probable source for the microgranite ring dyke melt. In addition, a second source with low oxygen isotope ratios (e.g. basic rocks) probably contributed to the melt and possibly triggered the climactic eruption of the Teplice rhyolite as well as the crystal-rich intrusion of the ring dyke.
The sources and critical enrichment processes for granite related tin ores are still not well understood. The Erzgebirge represents one of the classical regions for tin mineralization. We investigated the four largest plutons from the Western Erzgebirge (Germany) for the geochemistry of bulk rocks and autocrystic zircons and relate this information to their intrusion ages. The source rocks of the Variscan granites were identified as high-grade metamorphic rocks based on the comparison of Hf-O isotope data on zircons, the abundance of xenocrystic zircon ages as well as Nd and Hf model ages. Among these rocks, restite is the most likely candidate for later Variscan melts. Based on the evolution with time, we could reconstruct enrichment factors for tin and tungsten starting from the protoliths (575 Ma) that were later converted to high-grade metamorphic rocks (340 Ma) and served as sources for the older biotite granites (323–318 Ma) and the tin granites (315–314 Ma). This evolution involved a continuous enrichment of both tin and tungsten with an enrichment factor of ~15 for tin and ~7 for tungsten compared to the upper continental crust (UCC). Ore level concentrations (>10–100 times enrichment) were achieved only in the greisen bodies and dykes by subsequent hydrothermal processes.
Es werden einige Aufschlüsse auf dem Sonnenkamp in der Gemeinde Beim, 5 km östlich Osnabrück, beschrieben. Sie lassen erkennen, daß der drenthestadiale Vorstoß des Osnabrücker Gletschers hier eine lokale West-Ost-Richtung hatte. Zugleich lassen sie das Oszillieren einer Eisrandlage vermuten, die mit der Geschiebe-Akkumulation am Gattberg in Verbindung steht.
Toward parametrization of precipitating shallow cumulus cloud organization via moisture variance
(2021)
The influence of the initial vertical moisture profile on precipitating shallow cumulus cloud organization in terms of the column-averaged moisture variance is investigated using large-eddy simulations. Five idealized simulations based on the Rain in Cumulus over the Ocean field experiment with different initial moisture profiles are investigated. All cases simulate precipitating shallow cumulus convection in a marine sub-tropical region under large-scale subsidence. The results show that the moisture variance is mainly generated through the interaction of the moisture flux and the moisture gradient in the gradient production term at the top of the boundary layer. The development is characterized by three regimes: initial, transition, and quasi-steady regime. During the initial regime, the moisture gradient is built up by moisture accumulation until precipitating convection starts. Within the transition regime, precipitation enables mesoscale cloud organization with enhanced convective activity and moisture fluxes. The moisture variance increases from the moist to the dry initial moisture profiles. In a following quasi-steady regime, the moisture variance is approximately preserved. Thereby, the initial moisture gradient between the average sub-cloud layer and the free atmosphere is found to be an important factor for the generation of the quasi-steady column-averaged moisture variance. The result suggests that a resolved-scale variable like the moisture gradient can be used to estimate the quasi-steady state conditions resulting from cloud organization. This finding may serve as a starting point for the parametrization of the subgrid scale cloud organization caused by precipitating shallow convection.
Particulate matter (PM) largely consists of secondary organic aerosol (SOA) that is formed via oxidation of biogenic and anthropogenic volatile organic compounds (VOCs). Unambiguous identification of SOA molecules and their assignment to their precursor vapors are challenges that have so far only succeeded for a few SOA marker compounds, which are now well characterized and (partly) available as authentic standards. In this work, we resolve the complex composition of SOA by means of a top-down approach based on the newly created Aerosolomics database, which is fed by non-target analysis results of filter samples from oxidation flow reactor experiments. We investigated the oxidation products from the five biogenic VOCs α-pinene, β-pinene, limonene, 3-carene, and trans-caryophyllene and from the four anthropogenic VOCs toluene, o-xylene, 1,2,4-trimethylbenzene, and naphthalene. Using ultrahigh-performance liquid chromatography coupled to a high-resolution (Orbitrap) mass spectrometer, we determine the molecular formula of 596 chromatographically separated compounds based on exact mass and isotopic pattern. We utilize retention time and fragmentation mass spectra as a basis for unambiguous attribution of the oxidation products to their parent VOCs. Based on the molecular-resolved application of the database, we are able to assign roughly half of the total signal of oxygenated hydrocarbons in ambient suburban PM2.5 to one of the nine studied VOCs. The application of the database enabled us to interpret the appearance of diurnal compound clusters that are formed by different oxidation processes. Furthermore, by performing a hierarchical cluster analysis (HCA) on the same set of filter samples, we identified compound clusters that depend on sulfur dioxide mixing ratio and temperature. This study demonstrates how Aerosolomics tools (database and HCA) applied to PM filter samples can improve our understanding of SOA sources, their formation pathways, and temperature-driven partitioning of SOA compounds.
Particulate matter (PM) largely consists of secondary organic aerosol (SOA) that is formed via oxidation of biogenic and anthropogenic volatile organic compounds (VOCs). Unambiguous identification of SOA molecules and their assignment to their precursor vapors is a challenge that has so far only succeeded for a few SOA marker compounds, which are now well characterized and (partly) available as authentic standards. In this work, we resolve the complex composition of SOA by a top-down approach based on a newly created aerosolomics database, which is fed by non-target analysis results of filter samples from oxidation flow reactor experiments. We investigated the oxidation products from the five biogenic VOCs α-pinene, β-pinene, limonene, 3-carene, and trans-caryophyllene and from the four anthropogenic VOCs toluene, o-xylene, 1,2,4-trimethylbenzene, and naphthalene. Using ultra-high performance liquid chromatography coupled to a high-resolution (Orbitrap) mass spectrometer, we determine the molecular formula of 596 chromatographically separated compounds based on exact mass and isotopic pattern. We utilize retention time and fragmentation mass spectra as a basis for unambiguous attribution of the oxidation products to their parent VOCs. Based on the molecular-resolved application of the database, we are able to assign roughly half of the total signal of oxygenated hydrocarbons in ambient suburban PM2.5 to one of the nine studied VOCs. The application of the database enabled us to interpret the appearance of diurnal compound clusters that are formed by different oxidation processes. Furthermore, the application of a hierarchical cluster analysis (HCA) on the same set of filter samples enabled us to identify compound clusters that depend on sulfur dioxide mixing ratio and temperature. This study demonstrates how aerosolomics tools (database and HCA) applied on PM filter samples can improve our understanding of SOA sources, their formation pathways, and temperature-driven partitioning of SOA compounds.
Upper mantle shear zones are complex systems where deformation is commonly closely interacting with metamorphic (solid-solid) and/or melt/fluid-rock reactions. Here, feedback processes between deformation, reactions, grain size reduction and phase mixing result in strain weakening and the localization of deformation. The expression of these interlinked processes is portrayed by the microfabrics of strained peridotites and pyroxenites. The present thesis is focusing on these processes and their impact on the deformation in three upper mantle shear zones situated in the peridotite massifs of Lanzo (Italian Alps), Erro-Tobbio (Italian Alps) and Ronda (Betic Cordillera, Spain). In all three shear zones, the presence of melt led to phase mixing either by interstitial crystallization of pyroxenes from a Si-saturated and partially also highly evolved melt or by melt-rock reactions of pyroxene porphyroclasts with a Si-undersaturated melt. The effect of melt on the localization of strain is twofold and variable. Enhanced deformation by melt-wetted boundaries is assumed for all shear zones. Additionally, phase mixing by crystallization of interstitial pyroxenes or melt-rock reactions reduce or maintain the grain size by the formation of fine grained neoblasts and secondary phase boundary pinning. In this regard, pre- to early syn-kinematic, map-scale percolation of OH-bearing, evolved melts in the NW Ronda peridotite massif and the associated crystallization of interstitial pyroxenes result in the activation of grain size sensitive deformation mechanisms in the entire melt-effected area. In the rocks collected at Erro-Tobbio, syn-kinematic melt-rock reactions of pyroxene porphyroclasts and Si-undersaturated melt led to the formation of ultramylonitic neoblast tails (grain size ~10 μm). Compared to the adjacent coarser-grained olivine-dominated matrix, the activation of diffusion creep led to an increase in the strain rate by an order of magnitude within interconnected ultramylonitic layers. Strain localization and softening in ultramylonitic layers are also documented in the Lanzo samples. Neoblast tails of pyroxene porphyroclasts were likewise identified as their precursor. The phase assemblage of the tails, including ortho- and clinopyroxene, olivine, plagioclase, and spinel (± amphibole), and their geochemical trends suggest, unlike in Erro-Tobbio, a formation by continuous net-transfer reactions enhanced by the spinel lherzolite to plagioclase lherzolite transition.
The new results obtained from the three studied shear zones underscore the importance of reactions for the interlinked processes of grain size reduction, phase mixing, strain localization and strain softening in upper mantle shear zones. Concerning strain localization, the nature of the reaction (solid-solid, melt/fluid-rock) seems to play a subordinate role compared to its timing. Pre- to early syn-kinematic melt-triggered reactions result in strain localization along map-scale shear zones. Late stage syn-kinematic melt-rock or metamorphic reactions under high stress conditions are capable of localizing the deformation along discrete, sub-centimeter thick ultramylonites.
A graph theoretical approach to the analysis, comparison, and enumeration of crystal structures
(2008)
As an alternative approach to lattices and space groups, this work explores graph theory as a means to model crystal structures. The approach uses quotient graphs and nets - the graph theoretical equivalent of cells and lattices - to represent crystal structures. After a short review of related work, new classes of cycles in nets are introduced and their ability to distinguish between non-isomorphic nets and their computational complexity are evaluated. Then, two methods to estimate a structure’s density from the corresponding net are proposed. The first uses coordination sequences to estimate the number of nodes in a sphere, whereas the second method determines the maximal volume of a unit cell. Based on the quotient graph only, methods are proposed to determine whether nets consist of islands, chains, planes, or penetrating, disconnected sub-nets. An algorithm for the enumeration of crystal structures is revised and extended to a search for structures possessing certain properties. Particular attention is given to the exclusion of redundant nets and those, which, by the nature of their connectivity, cannot correspond to a crystal structure. Nets with four four-coordinated nodes, corresponding to sp3 hybridised carbon polymorphs with four atoms per unit cell, are completely enumerated in order to demonstrate the approach. In order to render quotient graphs and nets independent from crystal structures, they are reintroduced in a purely graph-theoretical way. Based on this, the issue of iso- and automorphism of nets is reexamined. It is shown that the topology of a net (that is the bonds in a crystal) constrains severely the symmetry of the embedding (that is the crystal), and in the case of connected nets the space group except for the setting. Several examples are studied and conclusions on phases are drawn (pseudo-cubic FeS2 versus pyrite; α- versus β- quartz; marcasite- versus rutile-like phases). As the automorphisms of certain quotient graphs stipulate a translational symmetry higher than an arbitrary embedding of the corresponding net would show, they are examined in more detail and a method to reduce the size of such quotient graphs is proposed. Besides two instructional examples with 2-dimensional graphs, the halite, calcite, magnesite, barytocalcite, and a strontium feldspar structures are discussed. For some of the structures it is shown that the quotient graph which is equivalent to a centred cell is reduced to a quotient graph equivalent to the primitive cell. For the partially disordered strontium feldspar, it is shown that even if it could be annealed to an ordered structure, the unit cell would likely remain unchanged. For the calcite and barytocalcite structures it is shown that the equivalent nets are not isomorphic.
Bei Damme, Gehrde und Rieste, 30 km nordöstlich von Osnabrück, kommt ein marin-sedimentäres, stratiformes Eisenerzlager vor, das aus Brauneisenerz-Geröllen und mergelig-glaukonitischer Matrix besteht und meist 2-7 m mächtig ist. Dieses Erzlager tritt in fünf unterschiedlich großen, linsenförmigen Zonen auf, die in 70-400 m Tiefe unter Gelände auf den flach einfallenden Flügeln einer 35 km langen und 10km breiten Oberkreide-Mulde liegen. Es gehört stratigraphisch dem Oberen Unter-Campan an und transgrediert auf tonige Gesteine der Unterkreide. In seinem Hangenden liegen Sedimentgesteine des Ober-Campan, Tertiär und Quartär. Das Erzlager entstand als marine Seife durch Abtragung, Umlagerung und Oxidation von Siderit-Konkretionen aus den tonigen Gesteinen der Unterkreide im Liegenden und in der Umgebung des Erzvorkommens. Von 1944-1967 ist das Erzlager in der jetzt auflässigen Grube Damme abgebaut worden. Dort erzeugte man aus Roherz mit 30-32 % Fe und 0,6-0,7% P durch naßmechanische Aufbereitung ein Konzentrat (versandfertiges Produkt) mit 46-47 % Fe und 0,8% P, das im Ruhrgebiet verhüttet wurde. Insgesamt wurden rund 9,2 Mio. t Roherz gefördert und 5,1 Mio. t Konzentrat erzeugt. Die Grube Damme ist aus wirtschaftlichen Gründen stillgelegt worden. Das Erz ist gegenwärtig nicht abbauwürdig. Deshalb sind die Erzvorräte noch nicht vollständig erkundet.
This thesis presents microstructural investigations of rock salt from the central part of the Gorleben salt dome (Northern Germany). The main emphasis was to characterize the rock salt microfabrics, to identify operating deformation mechanisms in halite and anhydrite and to decipher the macro- and microstructural distribution of hydrocarbons, which have been encountered during the underground exploration of the salt dome. The microfabrics of the Knäuel- and the Streifensalz formation indicate that strain-induced grain boundary migration has been active during deformation of halite. Crystal plastic deformation of halite is further documented by lattice bending, subgrain formation and minor subgrain rotation. Evidence for pressure solution of halite has not been found, but cannot be excluded because of the small grain size, the lack of LPO and the low differential stress (1.1 - 1.3 MPa) as deduced from subgrain-size piezometry. Solution precipitation creep was proven for intercalated anhydrite layers and clusters, which have been deformed in the brittle-ductile regime. Brittle deformation of anhydrite in terms of boudinage and fracturing was counteracted by viscous creep of halite which caused a re-sealing of fractures and a reestablishing of the characteristic sealing capacity of rock salt. Hydrocarbons are mainly located along cross cut 1 West of the Gorleben exploration mine and are heterogeneously distributed in the rock salt. They are incorporated in the rock salt foliation in the form of streaks, dispersed clouds, clusters and isolated patches. On the micro-scale, hydrocarbons are trapped along grain boundaries of halite and/or anhydrite, in micro-capillary tubes of anhydrite and in pore space of the rare rock salt with elevated porosity (< 1.26 vol.-%). Such elevated porosities correlate with elevated hydrocarbon concentrations of several hundred ppm. The overall concentrations of hydrocarbons, however, are very low (< 0.05 wt.-%). Elevated porosity is depicted to be a remnant originating from an early stage of salt uplift when fluid and hydrocarbons have migrated and spread from the Staßfurt Karbonat (z2SK) into the superjacent Gorleben Hauptsalz. During halokinesis and the strong reworking of the salt body hydrocarbons have been redistributed and dismembered resulting in the isolated present-day occurrences. The distribution of hydrocarbons shows no relation to local variations in the rock salt fabric. The microstructures of hydrocarbon-bearing and hydrocarbon-free Gorleben rock salt are not distinguishable from each other. Likewise, the presence of hydrocarbons should not have influenced the mechanical behavior or the rock salt as indicated by the microfabrics studied and by geomechanical data. The pure amounts of hydrocarbons are too low for any detectable impact on the barrier properties of this part of rock salt. Although hydrocarbons have migrated into the Gorleben Hauptsalz during an early stage of salt uplift when the sealing capacity of rock salt was diminished, the major implication of their isolated distribution patterns is that the Gorleben rock salt was able to regain its sealing capacity during subsequent deformation and re-equilibration. Former migration pathways for fluid and hydrocarbons have been healed and do not exist anymore. The application of X-ray computed tomography (CT) allows the 3D visualization and quantification of anhydrite, pore space and fluid phases located along grain-boundaries or trapped as intracrystalline inclusions. The 3D reconstruction of anhydrite clusters and pore space for the same sample reveals different spatial distribution patterns. This fact implies that anhydrite is not responsible for such elevated pore space in the rock salt studied, which has been largely closed during the polyphase deformation history of the Gorleben salt dome. High-resolution nanoCT scans (≤ 1 μm voxel size) of single intra- and intercrystalline fluid inclusions in rock salt enable a characterization of gaseous, solid and liquid phases inside single fluid inclusions and give exact information on morphology and shape. The 3D reconstruction of grain boundary fluid inclusions allows the amount, volumes, surface areas or diameters of various types to be determined. Non-destructive X-ray CT imaging is presented as very useful tool to characterize the structural inventory of rock salt. This non-destructive technique offers new perspectives for microstructural studies and for a wide range of research in structural geology, in general.
[Nachruf] Arno Semmel
(2010)
Non-technical summary: There has been a long history of conflicts, studies, and debate over how to both protect rivers and develop them sustainably. With a pause in new developments caused by the global pandemic, anticipated further implementation of the Paris Agreement and high-level global climate and biodiversity meetings in 2021, now is an opportune moment to consider the current trajectory of development and policy options for reconciling dams with freshwater system health. Technical summary: We calculate potential loss of free-flowing rivers (FFRs) if proposed hydropower projects are built globally. Over 260,000 km of rivers, including Amazon, Congo, Irrawaddy, and Salween mainstem rivers, would lose free-flowing status if all dams were built. We propose a set of tested and proven solutions to navigate trade-offs associated with river conservation and dam development. These solution pathways are framed within the mitigation hierarchy and include (1) avoidance through either formal river protection or through exploration of alternative development options; (2) minimization of impacts through strategic or system-scale planning or re-regulation of downstream flows; (3) restoration of rivers through dam removal; and (4) mitigation of dam impacts through biodiversity offsets that include restoration and protection of FFRs. A series of examples illustrate how avoiding or reducing impacts on rivers is possible – particularly when implemented at a system scale – and can be achieved while maintaining or expanding benefits for climate resilience, water, food, and energy security. Social media summary: Policy solutions and development pathways exist to navigate trade-offs to meet climate resilience, water, food, and energy security goals while safeguarding FFRs.
Global water models (GWMs) simulate the terrestrial water cycle, on the global scale, and are used to assess the impacts of climate change on freshwater systems. GWMs are developed within different modeling frameworks and consider different underlying hydrological processes, leading to varied model structures. Furthermore, the equations used to describe various processes take different forms and are generally accessible only from within the individual model codes. These factors have hindered a holistic and detailed understanding of how different models operate, yet such an understanding is crucial for explaining the results of model evaluation studies, understanding inter-model differences in their simulations, and identifying areas for future model development. This study provides a comprehensive overview of how state-of-the-art GWMs are designed. We analyze water storage compartments, water flows, and human water use sectors included in 16 GWMs that provide simulations for the Inter-Sectoral Impact Model Intercomparison Project phase 2b (ISIMIP2b). We develop a standard writing style for the model equations to further enhance model improvement, intercomparison, and communication. In this study, WaterGAP2 used the highest number of water storage compartments, 11, and CWatM used 10 compartments. Seven models used six compartments, while three models (JULES-W1, Mac-PDM.20, and VIC) used the lowest number, three compartments. WaterGAP2 simulates five human water use sectors, while four models (CLM4.5, CLM5.0, LPJmL, and MPIHM) simulate only water used by humans for the irrigation sector. We conclude that even though hydrologic processes are often based on similar equations, in the end, these equations have been adjusted or have used different values for specific parameters or specific variables. Our results highlight that the predictive uncertainty of GWMs can be reduced through improvements of the existing hydrologic processes, implementation of new processes in the models, and high-quality input data.
Global water models (GWMs) simulate the terrestrial water cycle on the global scale and are used to assess the impacts of climate change on freshwater systems. GWMs are developed within different modelling frameworks and consider different underlying hydrological processes, leading to varied model structures. Furthermore, the equations used to describe various processes take different forms and are generally accessible only from within the individual model codes. These factors have hindered a holistic and detailed understanding of how different models operate, yet such an understanding is crucial for explaining the results of model evaluation studies, understanding inter-model differences in their simulations, and identifying areas for future model development. This study provides a comprehensive overview of how 16 state-of-the-art GWMs are designed. We analyse water storage compartments, water flows, and human water use sectors included in models that provide simulations for the Inter-Sectoral Impact Model Intercomparison Project phase 2b (ISIMIP2b). We develop a standard writing style for the model equations to enhance model intercomparison, improvement, and communication. In this study, WaterGAP2 used the highest number of water storage compartments, 11, and CWatM used 10 compartments. Six models used six compartments, while four models (DBH, JULES-W1, Mac-PDM.20, and VIC) used the lowest number, three compartments. WaterGAP2 simulates five human water use sectors, while four models (CLM4.5, CLM5.0, LPJmL, and MPI-HM) simulate only water for the irrigation sector. We conclude that, even though hydrological processes are often based on similar equations for various processes, in the end these equations have been adjusted or models have used different values for specific parameters or specific variables. The similarities and differences found among the models analysed in this study are expected to enable us to reduce the uncertainty in multi-model ensembles, improve existing hydrological processes, and integrate new processes.
Herein, the high-pressure/high-temperature synthesis (11 GPa, 650 °C) of Tb3B10O17(OH)5 in a modified Walker-type multianvil device is presented. The structure of this rare-earth borate was determined by single-crystal X-ray diffraction methods and was found to crystallize orthorhombically in the space group Pmn21 (no. 31) with the unit cell parameters a = 16.2527(4), b = 4.4373(1), and c = 8.8174(2) Å. The new compound was further characterized using infrared spectroscopy, energy-dispersive X-ray spectroscopy, second harmonic generation (SHG) measurements, and temperature-dependent X-ray powder diffraction. Tb3B10O17(OH)5 decomposes to β-Tb(BO2)3 at temperatures higher than 460 °C. With increasing temperatures, the formation of μ-TbBO3 was observed, which transforms to π-TbBO3 upon cooling.
High-pressure/high-temperature synthesis of the new boron-rich terbium hydroxyborate Tb3B12O19(OH)7
(2023)
Monoclinic Tb3B12O19(OH)7 was obtained by multianvil high-pressure/high-temperature syntheses at 6 GPa and 650 °C. The crystal structure was investigated by single-crystal X-ray diffraction methods and space group C2 (no. 5) with the unit cell parameters a = 24.2299(5) Å, b = 4.4667(1) Å, c = 7.0964(2) Å, β = 94.58(1)°, and two formula units per cell were revealed. Powder X-ray diffraction, infrared spectroscopy and the investigation of its second harmonic generation properties support the proposed structural model.
We investigate the contribution of oceanic methyl iodide (CH3I) to the stratospheric iodine budget. Based on CH3I measurements from three tropical ship campaigns and the Lagrangian transport model FLEXPART, we provide a detailed analysis of CH3I transport from the ocean surface to the cold point in the upper tropical tropopause layer (TTL). While average oceanic emissions differ by less than 50% from campaign to campaign, the measurements show much stronger variations within each campaign. A positive correlation between the oceanic CH3I emissions and the efficiency of CH3I troposphere–stratosphere transport has been identified for some cruise sections. The mechanism of strong horizontal surface winds triggering large emissions on the one hand and being associated with tropical convective systems, such as developing typhoons, on the other hand, could explain the identified correlations. As a result of the simultaneous occurrence of large CH3I emissions and strong vertical uplift, localized maximum mixing ratios of 0.6 ppt CH3I at the cold point have been determined for observed peak emissions during the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere)-Sonne research vessel campaign in the coastal western Pacific. The other two campaigns give considerably smaller maxima of 0.1 ppt CH3I in the open western Pacific and 0.03 ppt in the coastal eastern Atlantic. In order to assess the representativeness of the large local mixing ratios, we use climatological emission scenarios to derive global upper air estimates of CH3I abundances. The model results are compared with available upper air measurements, including data from the recent ATTREX and HIPPO2 aircraft campaigns. In the eastern Pacific region, the location of the available measurement campaigns in the upper TTL, the comparisons give a good agreement, indicating that around 0.01 to 0.02 ppt of CH3I enter the stratosphere. However, other tropical regions that are subject to stronger convective activity show larger CH3I entrainment, e.g., 0.08 ppt in the western Pacific. Overall our model results give a tropical contribution of 0.04 ppt CH3I to the stratospheric iodine budget. The strong variations in the geographical distribution of CH3I entrainment suggest that currently available upper air measurements are not representative of global estimates and further campaigns will be necessary in order to better understand the CH3I contribution to stratospheric iodine.
We investigate the contribution of oceanic methyl iodide (CH3I) to the stratospheric iodine budget. Based on CH3I measurements during three tropical ship campaigns and the Lagrangian transport model FLEXPART we provide a detailed analysis of CH3I transport from the ocean surface to the cold point in the upper tropical tropopause layer (TTL). While average oceanic emissions differ by less than 50% from campaign to campaign, the measurements show much stronger variations within each campaign. A positive correlation between the oceanic CH3I emissions and the efficiency of CH3I troposphere–stratosphere transport has been identified for some cruise sections. The mechanism of strong horizontal surface winds triggering large emissions on the one hand and being associated with tropical convective systems, such as developing typhoons, on the other hand, could explain the identified correlations. As a result of the simultaneous occurrence of large CH3I emissions and strong vertical uplift, localized maximum mixing ratios of 0.6 ppt CH3I at the cold point have been determined for observed peak emissions during the SHIVA-Sonne campaign in the coastal West Pacific. The other two campaigns give considerable smaller maxima of 0.1 ppt CH3I for the TransBrom campaign in the open West Pacific and 0.03 ppt for emissions from the coastal East Atlantic during the DRIVE campaign. In order to assess the representativeness of the large local mixing ratios we use climatological emission scenarios to derive global upper air estimates of CH3I abundances. The model results are compared to available upper air measurements including data from the recent ATTREX and HIPPO2 aircraft campaigns. In the East Pacific region, the location of the available measurement campaigns in the upper TTL, the comparisons give a good agreement indicating that around 0.01 to 0.02 ppt of CH3I enter the stratosphere. However, other tropical regions, which are subject to stronger convective activity show larger CH3I entrainment, e.g., 0.08 ppt in the West Pacific. The strong variations in the geographical distribution of CH3I entrainment suggest that currently available upper air measurements are not representative of global estimates and further campaigns will be necessary in order to better understand the CH3I contribution to stratospheric iodine.
The accurate knowledge of the groundwater storage variation (ΔGWS) is essential for reliable water resource assessment, particularly in arid and semi-arid environments (e.g., Australia, the North China Plain (NCP)) where water storage is significantly affected by human activities and spatiotemporal climate variations. The large-scale ΔGWS can be simulated from a land surface model (LSM), but the high model uncertainty is a major drawback that reduces the reliability of the estimates. The evaluation of the model estimate is then very important to assess its accuracy. To improve the model performance, the terrestrial water storage variation derived from the Gravity Recovery And Climate Experiment (GRACE) satellite mission is commonly assimilated into LSMs to enhance the accuracy of the ΔGWS estimate. This study assimilates GRACE data into the PCRaster Global Water Balance (PCR-GLOBWB) model. The GRACE data assimilation (DA) is developed based on the three-dimensional ensemble Kalman smoother (EnKS 3D), which considers the statistical correlation of all extents (spatial, temporal, vertical) in the DA process. The ΔGWS estimates from GRACE DA and four LSM simulations (PCR-GLOBWB, the Community Atmosphere Biosphere Land Exchange (CABLE), the Water Global Assessment and Prognosis Global Hydrology Model (WGHM), and World-Wide Water (W3)) are validated against the in situ groundwater data. The evaluation is conducted in terms of temporal correlation, seasonality, long-term trend, and detection of groundwater depletion. The GRACE DA estimate shows a significant improvement in all measures, notably the correlation coefficients (respect to the in situ data) are always higher than the values obtained from model simulations alone (e.g., ~0.15 greater in Australia, and ~0.1 greater in the NCP). GRACE DA also improves the estimation of groundwater depletion that the models cannot accurately capture due to the incorrect information of the groundwater demand (in, e.g., PCR-GLOBWB, WGHM) or the unavailability of a groundwater consumption routine (in, e.g., CABLE, W3). In addition, this study conducts the inter-comparison between four model simulations and reveals that PCR-GLOBWB and CABLE provide a more accurate ΔGWS estimate in Australia (subject to the calibrated parameter) while PCR-GLOBWB and WGHM are more accurate in the NCP (subject to the inclusion of anthropogenic factors). The analysis can be used to declare the status of the ΔGWS estimate, as well as itemize the possible improvements of the future model development.
has been demonstrated in climate models that both the Indian and East Asian summer monsoons (ISM and EASM) are strengthened by the uplift of the entire Asian orography or Tibetan Plateau (TP) (i.e. bulk mountain uplift). Such an effect is widely perceived as the major mechanism contributing to the evolution of Asian summer monsoons in the Neogene. However, geological evidence suggests more diachronous growth of the Asian orography (i.e. regional mountain uplift) than bulk mountain uplift. This demands a re-evaluation of the relation between mountain uplift and the Asian monsoon in the geological periods. In this study, sensitivity experiments considering the diachronous growth of different parts of the Asian orography are performed using the regional climate model COSMO-CLM to investigate their effects on the Asian summer monsoons. The results show that, different from the bulk mountain uplift, the regional mountain uplift can lead to an asynchronous development of the ISM and EASM. While the ISM is primarily intensified by the thermal insulation (mechanical blocking) effect of the southern TP (Zagros Mountains), the EASM is mainly enhanced by the surface sensible heating of the central, northern and eastern TP. Such elevated surface heating can induce a low-level cyclonic anomaly around the TP that reduces the ISM by suppressing the lower tropospheric monsoon vorticity, but promotes the EASM by strengthening the warm advection from the south of the TP that sustains the monsoon convection. Our findings provide new insights to the evolution of the Asian summer monsoons and their interaction with the tectonic changes in the Neogene.
The Late Miocene (11.6–5.3 Ma) is a crucial period in the history of the Asian monsoon. Significant changes in the Asian climate regime have been documented for this period, which saw the formation of the modern Asian monsoon system. However, the spatiotemporal structure of these changes is still ambiguous, and the associated mechanisms are debated. Here, we present a simulation of the average state of the Asian monsoon climate for the Tortonian (11–7 Ma) using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1° × 1°) and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our regional Tortonian run shows a stronger-than-present East Asian winter monsoon wind as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered present-day northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. Precipitation decreases in northern China and northern India, but increases in southern China, the western coast and the southern tip of India. This can be attributed to the changes in both the regional topography (e.g. the lower northern Tibetan Plateau) and the global climate conditions (e.g. the higher sea surface temperature). The spread of dry summer conditions over northern China and northern Pakistan in our Tortonian run further implies that the monsoonal climate may not have been fully established in these regions in the Tortonian. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better characterizes the convective activity and its response to regional topographical changes. It therefore provides a useful and compared to global models, a complementary tool to improve our understanding of the Asian monsoon evolution in the Late Miocene.
In the last decade, the Climate Limited-area Modeling (CLM) Community has contributed to the Coordinated Regional Climate Downscaling Experiment (CORDEX) with an extensive set of regional climate simulations. Using several versions of the COSMO-CLM community model, ERA-Interim reanalysis and eight Global Climate Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) were dynamically downscaled with horizontal grid spacings of 0.44◦(∼50 km), 0.22◦ (∼25 km) and 0.11◦ (∼12 km) over the CORDEX domains Europe, South Asia, East Asia, Australasia and Africa. This major effort resulted in 80 regional climate simulations publicly available through the Earth System Grid Federation (ESGF) web portals for use in impact studies and climate scenario assessments. Here we review the production of these simulations and assess their results in terms of mean near-surface temperature and precipitation to aid the future design of the COSMO-CLM model simulations. It is found that a domain-specific parameter tuning is beneficial, while increasing horizontal model resolution (from 50 to 25 or 12 km grid spacing) alone does not always improve the performance of the simulation. Moreover, the COSMO-CLM performance depends on the driving data. This is generally more important than the dependence on horizontal resolution, model version and configuration. Our results emphasize the importance of performing regional climate projections in a coordinated way, where guidance from both the global (GCM) and regional (RCM) climate modelling communities is needed to increase the reliability of the GCM-RCM modelling chain.
In the last decade, the Climate Limited-area Modeling Community (CLM-Community) has contributed to the Coordinated Regional Climate Downscaling Experiment (CORDEX) with an extensive set of regional climate simulations. Using several versions of the COSMO-CLM-Community model, ERA-Interim reanalysis and eight global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) were dynamically downscaled with horizontal grid spacings of 0.44∘ (∼ 50 km), 0.22∘ (∼ 25 km), and 0.11∘ (∼ 12 km) over the CORDEX domains Europe, South Asia, East Asia, Australasia, and Africa. This major effort resulted in 80 regional climate simulations publicly available through the Earth System Grid Federation (ESGF) web portals for use in impact studies and climate scenario assessments. Here we review the production of these simulations and assess their results in terms of mean near-surface temperature and precipitation to aid the future design of the COSMO-CLM model simulations. It is found that a domain-specific parameter tuning is beneficial, while increasing horizontal model resolution (from 50 to 25 or 12 km grid spacing) alone does not always improve the performance of the simulation. Moreover, the COSMO-CLM performance depends on the driving data. This is generally more important than the dependence on horizontal resolution, model version, and configuration. Our results emphasize the importance of performing regional climate projections in a coordinated way, where guidance from both the global (GCM) and regional (RCM) climate modeling communities is needed to increase the reliability of the GCM–RCM modeling chain.
Evidence of widespread wildfires in a coal seam from the middle Permian of the North China Basin
(2017)
The North China Basin is the largest coal-bearing basin in China, and has an areal extent of 800,000 km2. We analyzed 138 coal samples and in situ pillar coal samples of the middle Permian from this basin by macropetrography, microscope, scanning electron microscope, gas chromatography, and gas chromatography–mass spectrometer in order to study wildfires. High contents of inertinite (charcoal) and natural coke particles observed in coal samples indicate that vegetation in precursor mires and peats of the middle Permian coal from north China was exposed to far-ranging wildfires. In addition, high-molecular-weight polycyclic aromatic hydrocarbons were detected in the coal samples. These aromatic compounds were formed under high temperatures and provide further evidence of wildfire. These wildfires would have discharged significant CO and CO2 gases into the atmosphere and affected the paleoclimate and paleoecosystem.
State-of-the-art general circulation models (GCMs) are tested and challenged by the ability to reproduce paleoclimate key intervals. In order to account for climate changes associated with soil dynamics we have developed a soil scheme, which is asynchronously coupled to a state-of-the-art atmosphere ocean GCM with dynamic vegetation. We test the scheme for conditions representative of a warmer (mid-Holocene, 6 kyr before present, BP) and colder (Last Glacial Maximum, 21 kyr BP) than pre-industrial climate. The computed change of physical soil properties (i.e. albedo, water storage capacity, and soil texture) for these different climates leads to amplified global climate anomalies. Especially regions like the transition zone of desert/savannah and taiga/tundra, exhibit an increased response as a result of the modified soil treatment. In comparison to earlier studies, the inclusion of the soil feedback pushes our model simulations towards the warmer end in the range of mid-Holocene studies and beyond current estimates of global cooling during the Last Glacial Maximum based on PMIP2 (Paleoclimate Modelling Intercomparison Project 2) studies. The main impact of the interactive soil scheme on the climate response is governed by positive feedbacks, including dynamics of vegetation, snow, sea ice, local water recycling, which might amplify forcing factors ranging from orbital to tectonic timescales.
Until now, the NW Indian Ocean was sparsely covered with coral proxy records, and records from the Maldives Archipelago do not exist. The first such coral proxy record from the central Maldives is presented in this study. It originates from a massive Porites lutea (Quoy and Gaimard, 1833) colony that was sampled March 2007 in the lagoon of Rasdhoo Atoll (4°N/ 73°W), which is located in the central Maldives. The record spans a period of 90 yrs and reaches back to 1917 AD with monthly to bimonthly resolution. This study investigates temporal variations of the skeletal stable oxygen (delta18O) and carbon (delta13C) isotopes, the strontium-to-calcium (Sr/Ca), and the annual extension-rates, and their relationship to historical climate variations 1917-2007. Annual extension-rates show an increase over the 20th century, and are correlated with instrumental sea surface temperatures (SST). The interannual variation of the extension-rates within 2.5-4 years is driven by the El Niño-Southern Oscillation (ENSO). The amount of skeletal extension during the summer months is triggered by variations in the strength of the SW monsoon. Interannual and decadal variability in monsoon current activity (18-19 yrs) and rainfall over India are an expression of the summer monsoon strength. This is the reason why a statistical link between coral extension-rates and precipitation over India can be established. This implies that annual extension-rates in corals can be used as a new proxy for Indian monsoon variability on decadal resolution. The delta18O record exhibits the 20th century warming trend that is influenced by the effect of monsoon-induced cooling. delta18O also reveals interannual ENSO triggered variability, which is due to ENSO-forced variations in SST and sea surface salinity (SSS). A decadal variation at 12-14 yrs cannot be linked to SST variations in the NW Indian Ocean, but with decadal variations of SSS. They could be caused by ENSO- forced variations of the monsoon currents during the mature phase of ENSO teleconnections in the Indian Ocean in boreal winter. The Sr/Ca record does not indicate a significant warming, in spite of the observed SST rise at the sampling site. Changes in seawater Sr/Ca cannot be excluded. Nevertheless, interannual ENSO forcing is still evident. Evidence for the Pacific Decadal Oscillation (PDO) is found during 1917-1955. Afterwards, the Sr/Ca data indicate the disappearance of PDO forcing. By the combination of Sr/Ca and delta18O it is possible to detect ~80% of historical El Niño and La Niña events at the sample site. This study confirms the notion that interannual to multi-decadal climate fluctuations in the Pacific play a crucial role for climate variability in the Indian Ocean.
Nucleation and growth of aerosol particles from atmospheric vapors constitutes a major source of global cloud condensation nuclei (CCN). The fraction of newly formed particles that reaches CCN sizes is highly sensitive to particle growth rates, especially for particle sizes <10 nm, where coagulation losses to larger aerosol particles are greatest. Recent results show that some oxidation products from biogenic volatile organic compounds are major contributors to particle formation and initial growth. However, whether oxidized organics contribute to particle growth over the broad span of tropospheric temperatures remains an open question, and quantitative mass balance for organic growth has yet to be demonstrated at any temperature. Here, in experiments performed under atmospheric conditions in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN), we show that rapid growth of organic particles occurs over the range from −25 ∘C to 25 ∘C. The lower extent of autoxidation at reduced temperatures is compensated by the decreased volatility of all oxidized molecules. This is confirmed by particle-phase composition measurements, showing enhanced uptake of relatively less oxygenated products at cold temperatures. We can reproduce the measured growth rates using an aerosol growth model based entirely on the experimentally measured gas-phase spectra of oxidized organic molecules obtained from two complementary mass spectrometers. We show that the growth rates are sensitive to particle curvature, explaining widespread atmospheric observations that particle growth rates increase in the single-digit-nanometer size range. Our results demonstrate that organic vapors can contribute to particle growth over a wide range of tropospheric temperatures from molecular cluster sizes onward.
Northern Chile, which includes the extremely arid Atacama Desert and the semiarid Andean Highlands, has more than 100 basins with interior drainage; most contain salars (salt-ilncrusted playas). The area of interior drainage totals more than 38,000 square miles, within which salara and clay playas extend over a total area of about 2,800 square miles. In addition, hills and valleys in the Atacama Desert are extensively covered either with a thin hard saline crust, chiefly salt-cemented soil, or with a powdery soil that has a high content of saline material, chiefly anhydrite and gypsum. The region has an exceptional variety of types of hard saline crusts that are generally rare in other deserts, and many morphological and structural salt features, some of which may be unique. Soft saline crusts and clay playas, more characteristic of arid regions elsewhere, are also present. Hard salar crusts have formed by deposition of saline material in open water or by capillary migration and evaporation of near-surface ground water. Such crusts generally range from a few inches to several feet in thickness. Locally, crusts may attain thicknesses of several tens of feet, and one salar, Salar Grande, is a basin filled with high. purity rock salt to a local depth of at least 560 feet. Six general types of hard salar crusts are distinguished: (1) layered massive rock salt with a rugged surface, (2) slabby or nodular silty rock salt, (3) rugged gypsum or anhydrite, (4) massive coarsely crystalline rock salt, (5) smooth rock salt, and (6) silty nitrate-bearing saline crust. Soft surfaces or crusts include moist gypsum-bearing crusts, which commonly contain nodules and layers of ulexite in Andean salars, and moist to dry puffy soils and crusts that contain gypsum, thenardite and mirabilite as the principal saline constituents. An unusual chemical feature of the salars and the desert soils of northern Chile is the general paucity of carbonate minerals (for example, trona, calcite, and aragonite) which are widespread in other desert regions. Among the many morphological and structural features that can be recognized in and near salars of northern Chile, the most unusual occur in hard rock-salt crusts, which in themselves are scarce in other arid regions. Included are features due to corrosion of rock-salt crusts by windblown water or free-flowing surface water, such as: (1) salt cusps and crenulate margins of salars, (2) salt channels, (3) salt pseudobarchans, and (4) salt tubes. Constructional features in the salars include: (1) gypsum buttresses at borders of saline ponds, (2) salt veins, (3) salt stalactites, and (4) salt cones. In some salars, new fresh-water springs have formed steep-walled brine pools in thick rock-salt crusts. Prominent salt cascades and constructional salt terraces have been built up in one Andean valley by springs that are fed by brine from a nearby salar (Salar de Pedernales). Sag basins and prominent scarps occur along faults that cut through the salt mass of Salar Grande. Of, the 67 closed basins in the Andean Highlands of northern Chile, at least 35 show shorelines or deltas of former perennial lakes. Today only flve perennial lakes occur in this area. The former lakes probably formed at one or more times during the Pleistocene and perhaps continued to form into Holocene time. They indicate a climate that was either more rainy or cooler, or both, during the time of their formation. However, the absence of glacial features throughout most of the northern Chilean Andes indicates that the climate during the Pleistocene glacial stages was not greatly different from today's climate. It is estimated that perennial lakes would form in nearly all thil Andean basins if the mean annual rainfall of the region above 10,000 feet in altitude were increased to 15 inches from its present 8 inches, and if the mean annual temperature were about 2° F. less than it is at present.
In the Central German Uplands, Fagus sylvatica and Picea abies have been particularly affected by climate change. With the establishment of beech forests about 3000 years ago and pure spruce stands 500 years ago, they might be regarded as ‘neophytes’ in the Hessian forests. Palaeoecological investigations at wetland sites in the low mountain ranges and intramontane basins point to an asynchronous vegetation evolution in a comparatively small but heterogenous region. On the other hand, palynological data prove that sustainably managed woodlands with high proportions of Tilia have been persisting for several millennia, before the spread of beech took place as a result of a cooler and wetter climate and changes in land management. In view of increasingly warmer and drier conditions, Tilia cordata appears especially qualified to be an important silvicultural constituent of the future, not only due to its tolerance towards drought, but also its resistance to browsing, and the ability to reproduce vegetatively. Forest managers should be encouraged to actively promote the return to more stress-tolerant lime-dominated woodlands, similar to those that existed in the Subboreal chronozone.
Global distributions of profiles of sulphur hexafluoride (SF6) have been retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat covering the period September 2002 to March 2004. Individual SF6 profiles have a precision of 0.5 pptv below 25 km altitude and a vertical resolution of 4–6 km up to 35 km altitude. These data have been validated versus in situ observations obtained during balloon flights of a cryogenic whole-air sampler. For the tropical troposphere a trend of 0.230±0.008 pptv/yr has been derived from the MIPAS data, which is in excellent agreement with the trend from ground-based flask and in situ measurements from the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division. For the data set currently available, based on at least three days of data per month, monthly 5° latitude mean values have a 1 o standard error of 1%. From the global SF6 distributions, global daily and monthly distributions of the apparent mean age of air are inferred by application of the tropical tropospheric trend derived from MIPAS data. The inferred mean ages are provided for the full globe up to 90° N/S, and have a 1 o standard error of 0.25 yr. They range between 0 (near the tropical tropopause) and 7 years (except for situations of mesospheric intrusions) and agree well with earlier observations. The seasonal variation of the mean age of stratospheric air indicates episodes of severe intrusion of mesospheric air during each Northern and Southern polar winter observed, long-lasting remnants of old, subsided polar winter air over the spring and summer poles, and a rather short period of mixing with midlatitude air and/or upward transport during fall in October/November (NH) and April/May (SH), respectively, with small latitudinal gradients, immediately before the new polar vortex starts to form. The mean age distributions further confirm that SF6 is destroyed in the mesosphere to a considerable degree. Model calculations with the Karlsruhe simulation model of the middle atmosphere (KASIMA) chemical transport model agree well with observed global distributions of the mean age only if the SF6 sink reactions in the mesosphere are included in the model.
Recently, carbonates have attracted a lot of attention, due to the recognition of their importance in the global carbon cycle. This was enabled by improvement of the experimental techniques that allow for investigating the stability, structure, and physical properties of materials and high-pressures and high-temperatures, that is, they allow for investigating minerals and geochemical processes at the conditions occurring deep inside Earth. Although a lot of research has been focused on carbonates, there are still some open questions regarding their structure and physical properties at such extreme conditions. The aim of this thesis is to establish a deeper understanding of the nature of the phase transitions in carbonates by studying how do the atoms building up the crystal structure vibrate, that is lattice dynamics. The methodology adapted in this study is a combination of experimental and computational methods which allows for a very thorough examination of the problem. The computational approach allows to determine parameters that are elusive or tedious to measure, and the experimental results provide a solid benchmark for the calculations. This tandem of methods has been widely used for investigating lattice dynamics of various materials. In this study it was used to elucidate the structure and properties of carbonates in the deep Earth conditions
Biogenic NO emissions from soils (SNOx) play important direct and indirect roles in tropospheric chemistry. The most widely applied algorithm to calculate SNOx in global models was published 15 years ago by Yienger and Levy (1995), and was based on very few measurements. Since then, numerous new measurements have been published, which we used to build up a compilation of world wide field measurements covering the period from 1978 to 2010. Recently, several satellite-based top-down approaches, which recalculated the different sources of NOx (fossil fuel, biomass burning, soil and lightning), have shown an underestimation of SNOx by the algorithm of Yienger and Levy (1995). Nevertheless, to our knowledge no general improvements of this algorithm, besides suggested scalings of the total source magnitude, have yet been published. Here we present major improvements to the algorithm, which should help to optimize the representation of SNOx in atmospheric-chemistry global climate models, without modifying the underlying principals or mathematical equations. The changes include: (1) using a new landcover map, with twice the number of landcover classes, and using annually varying fertilizer application rates; (2) adopting a fraction of 1.0 % for the applied fertilizer lost as NO, based on our compilation of measurements; (3) using the volumetric soil moisture to distinguish between the wet and dry states; and (4) adjusting the emission factors to reproduce the measured emissions in our compilation (based on either their geometric or arithmetic mean values). These steps lead to increased global annual SNOx, and our total above canopy SNOx source of 8.6 Tg yr−1 (using the geometric mean) ends up being close to one of the satellite-based top-down approaches (8.9 Tg yr−1). The above canopy SNOx source using the arithmetic mean is 27.6 Tg yr−1, which is higher than all previous estimates, but compares better with a regional top-down study in eastern China. This suggests that both top-down and bottom-up approaches will be needed in future attempts to provide a better calculation of SNOx.
Soil biogenic NO emissions (SNOx) play important direct and indirect roles in chemical processes of the troposphere. The most widely applied algorithm to calculate SNOx in global models was published 15 years ago by Yienger and Levy (1995), was based on very few measurements. Since then numerous new measurements have been published, which we used to build up a atabase of field measurements conducted world wide covering the period from 1978 to 2009, including 108 publications with 560 measurements.
Recently, several satellite based top-down approaches, which recalculated the different sources of NOx (fossil fuel, biomass burning, soil and lightning), have shown an underestimation of SNOx by the algorithm of Yienger and Levy (1995). Nevertheless, to our knowledge no general improvements of this algorithm have yet been published.
Here we present major improvements to the algorithm, which should help to optimize the representation of SNOx in atmospheric-chemistry global climate models, without modifying the underlying principal or mathematical equations. The changes include: 1) Using a new up to date land cover map, with twice the number of land cover classes, and using annually varying fertilizer application rates; 2) Adopting the fraction of SNOx induced by fertilizer application based on our database; 3) Switching from soil water column to volumetric soil moisture, to distinguish between the wet and dry state; 4) Tuning the emission factors to reproduce the measured emissions in our database and calculate the emissions based on their mean value. These steps lead us to increased global yearly SNOx, and our total SNOx source ends up being close to one of the top-down approaches. In some geographical regions the new results agree better with the top-down approach, but there are also distinct differences in other regions. This suggests that a ombination of both top-down and bottom-up approaches could be combined in a future attempt to provide an even better calculation of SNOx.
Ca-Silikate als natürliche Einschlüsse in Diamanten sind so extrem selten und bislang wenig untersucht, daß der Weg, sie synthetisch herzustellen, um entsprechende Analysen durchführen zu können, gerechtfertigt wird. Um die Veränderungen über einen großen Druckbereich bis zu Bedingungen, die dem Unteren Erdmantel entsprechen, durchführen zu können, wurde ein neues Hochdrucklabor mit einer Multi-Anvil-Presse aufgebaut. In dieses Labor sind viele Erfahrungen aus eigenen Experimenten und aus anderen Arbeitsgruppen eingeflossen, sodaß eine leistungsfähige Hochdruckanlage zur Verfügung steht. Kernstück dieses Hochdrucksystems ist der innere Hochdruckaufbau, wobei nicht ein bereits etablierter Hochdruckaufbau kopiert, sondern - durch das Integrieren der Vorzüge von unterschiedlichen Systemen - ein eigenständiger Hochdruckaufbau entwickelt wurde. Das System ist für weitere Ausbaumöglichkeiten vorbereitet, sodaß z. B. großvolumige Kapseln zusammen mit den Ceramcast-Oktaedern bis 80 kbar eingesetzt werden können, bzw. der maximale Druckbereich mit einem 10/4 mm Aufbau bis über 200 kbar ausgeweitet werden kann. Die Untersuchung der Reaktionskinetik an den Ca-Silikatphasen stellt eine besondere Herausforderung dar. Aus vorangegangenen Experimenten und Untersuchungen ist die "nicht Quenchbarkeit" von Ca-Perovskit und die Amorphisierung von Ca-Walstromit bekannt, sodaß sich die Untersuchungen mittels der herkömmlichen Hochdruckmethoden für diese Fragestellung als nachteilig erweisen. Dank der Zusammenarbeit mit dem "Material Science Laboratory" am Synchrotron in Daresbury bot sich die Möglichkeit, in situ Hochdruckexperimente an den Ca-Silikatphasen durchzuführen. Es stand nur eine begrenzte Entwicklungszeit zur Verfügung, um die neuartige "fine-to-fine" Geometrie zu entwickeln und zu erproben. Mit diesem Hochdruckaufbau ist es gelungen, in situ Hochdruckexperimente bei bis zu 150 kbar und 1400°C durchzuführen und dabei Ca-Perovskit zu kristallisieren. Mit den kleineren 10mm MgO-Oktaedern und 5 bzw. 4 mm Truncation an den Wolframcarbid-Würfeln sind sogar bei gleicher Geometrie noch höhere Drücke realisierbar. Die Beobachtungen an den durchgeführten Experimente ermöglicht eine Aussage zur Reaktionskinetik der Phasenumwandlung bei Ca-Silikaten. Die Disproportionsreaktion von Ca-Perovskit zu den zwei Phasen Larnit und Si-Titanit läuft sehr rasch ab, wo hingegen die Rekombinationsreaktion dieser beiden Phasen zu Ca-Walstromit kinetisch gehemmt und innerhalb von Stunden keine Umwandlung beobachtet werden konnte. Darüber hinaus bestätigen die eigenen Experimente ein Einsetzen der Amorphisierung von Ca-Perovskit bei Drücken unterhalb von 10 kbar. Eine Amorphisierung von Ca-Walstromit wurde auch nach vollständiger Druckentlastung nicht beobachtet. Werden die Beobachtungen der kinetischen Experimente der Phasenumwandlung an Ca-Silikaten auf die natürlichen Bedingungen bei der Diamantentstehung und deren Aufstiegspfad übertragen, spricht dies für ein Modell des raschen Aufstiegs aus dem Unteren Mantel bzw. der Übergangszone und einem Steckenbleiben im Oberen Mantel bei moderaten Drücken. Der Weg an die Erdoberfläche findet dann zu einem späteren Zeitpunkt ebenfalls mit schnellen Aufstiegsgeschwindigkeiten statt. Die Ergebnisse der Löslichkeits-Hochdruckexperimente von Kalium und Phosphor bestätigen die Beobachtungen, die an den natürlichen Ca-Silikateinschlüssen gemacht wurden. In dem Zweiphasenfeld, in dem Larnit zusammen mit Si-Titanit koexsistiert, hebt sich vor allem die sehr hohe Löslichkeit von Kalium und Phosphor hervor. Zwar wurde bereits in den natürlichen Einschlüssen ein auffallend hoher Gehalt dieser Elemente beobacht, die Experimente zur maximalen Löslichkeit zeigen jedoch, daß sich weitaus höhere Gehalte im Larnit lösen können. Für diese Phase trifft die gekoppelte Substitution von Kalium und Phosphor gegen Calcium und Silicium im Verhältnis 1 : 1 zu. Interessant ist zudem die offenbare Druckhabhängigkeit der Löslichkeit in Larnit. Für eine geobarometrische Anwendung dieses Druckeffekts ist das Stabilitätsfeld mit nur 20 kbar relativ schmal, so daß der Druckgradient gering ist. Die Titanit-Struktur erweist sich im Gegensatz dazu als nicht kompatibel für diese Elemente. In Si-Titanit werden nur extrem geringe Gehalte an Kalium und Phosphor eingebaut. In den natürlichen Einschlüssen wurden gleichermaßen geringe Gehalte nachgewiesen. Damit kann vom Erreichen der maximalen Löslichkeit in den natürlichen Proben ausgegangen werden. Als potentieller Träger von Kalium und Phosphor in der Übergangszone ist die Phase Larnit. Sie kann sehr hohe Gehalte dieser Elemente aufnehmen, mit steigendem Druck nimmt die Löslichkeit jedoch ab. Direkte Messungen der Löslichkeit an Ca-Perovskit liegen bislang nicht vor. Die Experimente an der unteren Stabilitätsgrenze zeigen sehr geringe Gehalte an Kalium und Phosphor. Eine Substitution in dieser sehr dichten Struktur findet nicht statt. Die geringe Löslichkeit in Ca-Perovskit entspricht nicht dem erwarteten Ergebnis. Diese Phase galt bislang als möglicher Träger von Kalium und Phosphor im Unteren Mantel. Wenn davon ausgegangen wird, daß Einschlüsse, in denen Larnit und Si-Titanit nachgewiesen werden, möglicherweise ehemals Ca-Perovskit gewesen sind und damit eine Herkunft aus dem Unteren Mantel haben, so sprechen die hohen Gehalte an Kalium und Phosphor in Larnit gegen diese Annahme. Ein Einschluß, der als Ca-Perovskit im Unteren Mantel kristallisiert ist, kann nicht die großen Mengen an Kalium und Phosphor einbauen, wie sie dann im Larnit als direkte Umwandlungsphase nachgewiesen werden. Möglicherweise sind Einschlüsse, die hohe Gehalte an Kalium und Phosphor zeigen, in dem Zweiphasenstabilitätsfeld Larnit/Si-Titanit kristallisiert, und ein Hinweis darauf, daß sie kein Disproportionsprodukt aus vormaligem Ca-Perovskit sind. Bislang ungeklärt bleibt die Frage, ob mit höherem Druck die Löslichkeit von Kalium und Phosphor in Ca-Perovskit zunimmt. Wenn eine Druckabhängigkeit der Löslichkeit vorliegt, würde dies dafür sprechen, daß die Diamanten mit Ca-Perovskit-Einschlüssen aus dem Unteren Mantel stammen und nicht aus der Übergangszone. Die Annahme der Herkunft dieser speziellen Diamantparagenese aus dem Unteren Mantel wird auch durch das Auftreten von Ferro-Periklas und Stichovit zusammen mit Ca-Perovskit im gleichen Diamantkristall bekräftigt. Zukünftige Experimente bei höheren Drücken könnten die Frage klären, ob bei einer Druckerhöhung eine Zunahme der Löslichkeit in Ca-Perovskit beobachtet wird. Eine beachtliche Zunahme der Löslichkeit mit dem Druck würde das Modell der Herkunft der Ca-Silikateinschlüsse aus dem Unteren Mantel stützen. Die Löslichkeit von Kalium und Phosphor in Ca-Walstromit zeigt sowohl in den natürlichen Einschlüssen als auch in den Experimenten mittlere Gehalte dieser Elemente an. Abweichend von den Beobachtungen in den Einschlüssen ist jedoch der erhöhte Kaliumgehalt, der nicht den erwarteten stöchiometrischen Austausch von 1 : 1 wiedergibt. Untersuchungen an natürlichen Ca-Walstromit als Einschlüsse in Diamanten werden zukünftig von besonderem Interesse sein, da diese Einschlüsse entsprechend häufiger auftreten und als Probenmaterial vorliegen. Weitere Experimente im Ca-Walstromit-Stabilitätsfeld mit unterschiedlichen Gehalten an Spurenelementen und entsprechenden Strukturuntersuchungen können die Frage der Stabilität bzw. der Amorphisierung klären. Ein unmittelbares Amorphisieren von Ca-Walstromit nach der Druckentlastung wird nicht beobachtet und auch die energiereiche Strahlung der Mikrosonde bzw. des Synchrotrons hat keine Amorphisierung zur Folge. Beim Bestrahlen mit der sehr energiereichen Strahlung bei den TEM-Untersuchungen zeigt sich jedoch, daß Ca-Walstromit nicht sehr stabil ist und innerhalb weniger Minuten amorphisiert. Die TEM-Untersuchungen weisen auf mögliche Polymorphe von Ca-Walstromit hin. Wenn sich unterschiedliche Polymorphe nachweisen lassen, ist von abweichenden Löslichkeiten und unter Umständen anderen Einbaumechanismen in den Phasen auszugehen.
In der hier vorliegenden Arbeit wurden Spurenstoff-Flüsse zwischen Atmosphäre und Pedosphäre, sowie zwischen Atmosphäre und Vegetation untersucht. Der Austausch zwischen Atmosphäre und Boden wurde mit Hilfe von dynamischen Bodenkammern gemessen. Zur Bestimmung des Austauschs zwischen Atmosphäre und Biosphäre wurden Gradienten der Spurengase oberhalb der Baumkronen gemessen und daraus die Flüsse bestimmt. Weiterhin wurden methodische Vergleiche der Gradientmethode mit anderen Methoden (Relaxed-Eddy-Accumulation, Eddy- Correlation) durchgeführt. Die Untersuchungen mit Hilfe der Gaswechselkammern zeigen, dass während aller Messungen der Boden eine Senke von atmosphärischem Carbonylsulfid dargestellt hat. Hiermit wird die Rolle des Bodens als eine Senke für COS bestätigt. Die Depositonsraten betragen im Mittel - 0,81 pmolm exp -2 s exp -1 und besitzen eine Variabilität zwischen - 0,23 und - 1,38 pmolm exp -2 s exp -1. Im Vergleich zu den Literaturwerten (siehe Tabelle 1.1) sind die Aufnahmeraten des Bodens auf der Versuchsfläche "F1" schwach ausgeprägt. Im Vergleich zu anderen Arbeiten (siehe Lehmann & Conrad, 1996; Kesselmeier et al., 1999) sind keine eindeutigen Korrelationen zwischen dem COS-Fluss und der Lufttemperatur bzw. der Bodenfeuchte oder den Bodentemperaturen in 2, 5 und 10 cm zu erkennen. Diese hier aufgeführten Arbeiten beruhen jedoch auf Labormessungen mit nur sehr geringen homogenen und präparierten Bodenmengen. Die Feldmessungen im Rahmen dieser Arbeit wurden nicht unter vergleichbar definierten Bedingungen durchgeführt. Aufgrund zahlreicher beeinflussender Parameter und der vertikalen Inhomogenität des Bodens konnte jedoch auch nicht mit vergleichbar guten Korrelationen gerechnet werden. Eine saisonale Abhängigkeit der COS-Aufnahme ist über einen Zeitraum von 21 2 Monaten nicht ausgeprägt. Da die Messungen einer Kampagne im Mai 1999 aufgrund von Kontaminationen der Luftproben vollständig verworfen wurden, erstreckten sich die Messungen nur vom Hochsommer bis zum Frühherbst. Die räumliche Variabilität erreicht dagegen innerhalb einer Entfernung von 10 m eine Spanne zwischen - 0,43 und - 0,73 pmolm exp -2 s exp -1. Zurückzuführen ist dies auf die starke räumliche ....
Laut jüdischem Kalender entstand die Welt vor genau 5778 Jahren, nach der Bibel vor 6021 Jahren. Doch als Forscher begannen, auf und in der Erde selbst nach Spuren ihres Alters zu suchen, mussten sie die Zahl immer weiter nach oben korrigieren. Nach heutigen Datierungsmethoden ist unser Planet zwischen 4,5 und 4,6 Milliarden Jahre alt.
Volatile organic compounds (VOCs) were analyzed in air and snow samples at the Jungfraujoch high alpine research station in Switzerland as part of CLACE 5 (CLoud and Aerosol Characterization Experiment) during February/March 2006. The fluxes of individual compounds in ambient air were calculated from gas phase concentrations and wind speed. The highest concentrations and flux values were observed for the aromatic hydrocarbons benzene (14.3 μg.m−2 s−1), 1,3,5-trimethylbenzene (5.27 μg.m−2 s−1), toluene (4.40 μg.m−2 −1), and the aliphatic hydrocarbons i-butane (7.87 μg.m−2 s−1), i-pentane (3.61 μg.m−2 s−1) and n-butane (3.23 μg.m−2 s−1). The measured concentrations and fluxes were used to calculate the efficiency of removal of VOCs by snow, which is defined as difference between the initial and final concentration/flux values of compounds before and after wet deposition. The removal efficiency was calculated at −24°C (−13.7°C) and ranged from 37% (35%) for o-xylene to 93% (63%) for i-pentane. The distribution coefficients of VOCs between the air and snow phases were derived from published poly-parameter linear free energy relationship (pp-LFER) data, and compared with distribution coefficients obtained from the simultaneous measurements of VOC concentrations in air and snow at Jungfraujoch. The coefficients calculated from pp-LFER exceeded those values measured in the present study, which indicates more efficient snow scavenging of the VOCs investigated than suggested by theoretical predictions.
Volatile organic compounds (VOCs) were analyzed in air and snow samples at the Jungfraujoch high alpine research station in Switzerland as part of CLACE 5 (CLoud and Aerosol Characterization Experiment) during February/March 2006. The fluxes of individual compounds in ambient air were calculated from gas phase concentrations and wind speed. The highest flux values were observed for the aromatic hydrocarbons benzene (14.3 µg m−2s−1), 1,3,5-trimethylbenzene (5.27 µg m−2s−1), toluene (4.40 µg m−2s−1), and the aliphatic hydrocarbons i-butane (7.87 µg m−2s−1), i-pentane (3.61 µg m−2s−1) and n-butane (3.23 µg m−2s−1). The fluxes were used to calculate the efficiency of removal of VOCs by snow, and the effect of temperature on removal efficiency. The removal efficiency was calculated at – 24◦C (−13.7◦C) and ranged from 37% (35%) for o-xylene to 93% (63%) for i-pentane. The distribution coefficients of VOCs between the air and snow phases were derived from published poly-parameter linear free energy relationship (pp-LFER) data, and compared with distribution coef- ficients obtained from the simultaneous measurements of VOC concentrations in air and snow at Jungfraujoch. The coefficients calculated from pp-LFER exceeded those values measured in the present study, which indicates more efficient snow scavenging of the VOCs investigated than suggested by theoretical predictions.
Under the Kigali Amendment to the Montreal Protocol, new controls are being implemented to reduce emissions of HFC-23 (CHF3), a by-product during the manufacture of HCFC-22 (CHClF2). Starting in 2015, China and India, who dominate global HCFC-22 production (75% in 2017), set out ambitious programs to reduce HFC-23 emissions. Here, we estimate that these measures should have seen global emissions drop by 87% between 2014 and 2017. Instead, atmospheric observations show that emissions have increased and in 2018 were higher than at any point in history (15.9 ± 0.9 Gg yr−1). Given the magnitude of the discrepancy between expected and observation-inferred emissions, it is likely that the reported reductions have not fully materialized or there may be substantial unreported production of HCFC-22, resulting in unaccounted-for HFC-23 by-product emissions. The difference between reported and observation-inferred estimates suggests that an additional ~309 Tg CO2-equivalent emissions were added to the atmosphere between 2015 and 2017.
Within the world’s oceans, regionally distinct ecological niches develop due to differences in water temperature, nutrients, food availability, predation and light intensity. This results in differences in the vertical dispersion of planktonic foraminifera on the global scale. Understanding the controls on these modern-day distributions is important when using these organisms for paleoceanographic reconstructions. As such, this study constrains modern depth habitats for the northern equatorial Indian Ocean, for 14 planktonic foraminiferal species (G. ruber, G. elongatus, G. pyramidalis, G. rubescens, T. sacculifer, G. siphonifera, G. glutinata, N. dutertrei, G. bulloides, G. ungulata, P. obliquiloculata, G. menardii, G. hexagonus, G. scitula) using stable isotopic signatures (δ18O and δ13C) and Mg/Ca ratios. We evaluate two aspects of inferred depth habitats: (1) the significance of the apparent calcification depth (ACD) calculation method/equations and (2) regional species-specific ACD controls. Through a comparison with five global, (sub)tropical studies we found the choice of applied equation and δ18Osw significant and an important consideration when comparing with the published literature. The ACDs of the surface mixed layer and thermocline species show a tight clustering between 73–109 m water depth coinciding with the deep chlorophyll maximum (DCM). Furthermore, the ACDs for the sub-thermocline species are positioned relative to secondary peaks in the local primary production. We surmise that food source plays a key role in the relative living depths for the majority of the investigated planktonic foraminifera within this oligotrophic environment of the Maldives and elsewhere in the tropical oceans.
In Ergänzung zu einem vorangegangenen Projekt (Schönwiese et al., 2005) ist in der vorliegenden Studie eine weitere extremwertstatistische Untersuchung durchgeführt worden. Dazu wurden auf der Basis von täglichen Klimadaten aus Hessen und Umgebung (49°N bis 52°N, 7°O bis 11°O), und zwar der Temperatur von 53 Stationen und des Niederschlages von 84 Stationen, Schwellen extremer Werte definiert, um die Anzahl der Über- bzw. Unterschreitungen dieser Schwellen auf signifikante Trends hin zu untersuchen. Bei der Temperatur findet sich dabei eine systematische Zunahme von Hitzetagen (Maximumtemperatur über 30 °C) im August, wohingegen im Juli fast keine, und im Juni nur vereinzelt signifikante Zunahmen von Hitzetagen gefunden wurden. Hierbei zeigt sich, wie auch bei anderen Temperatur-Schwellen eine Abnahme der Signifikanz mit zunehmender Schwellenhöhe, was durch selteneres Auftreten besonders extremer Ereignisse verursacht wird. Im Winter und Frühjahr hat entsprechend die Anzahl der Frost- bzw. Eistage (Minimum- bzw. Maximumtemperatur unter 0 °C) signifikant abgenommen. Besonders ausgeprägt ist dies für die Frosttage im Frühling der Fall. Beim Niederschlag hat im Sommer, wiederum vor allem im August, die Anzahl von Trockentagen zugenommen. Extrem hohe Niederschlagssummen sind dagegen in dieser Jahreszeit seltener geworden, in den anderen Jahreszeiten jedoch häufiger. Vor allem der März zeichnet sich durch verbreitet hochsignifikante Zunahmen von Tagen mit Starkniederschlägen aus. Die Erhaltungsneigung von besonders warmen bzw. kalten Witterungen hat sich in den meisten Monaten nicht signifikant verändert. Es ist jedoch eine Neigung zu kürzeren relativ einheitlichen Witterungsabschnitten im Februar und März, sowie zu längeren im Oktober und November zu beobachten. Diese Ergebnisse sind jedoch vermutlich nicht sehr robust, da sich bei einer Verkürzung des Zeitfensters der Autokorrelationsfunktion die Signifikanzen teilweise (vor allem im April) deutlich verändern. Bei den Trends der Zahl der Trockenperioden erkennt man im Sommer einen positiven Trend; sie nehmen somit zu. Dies gilt sowohl für die 7-tägigen als auch für die 11-tägigen Trockenperioden. Die übrigen Jahreszeiten zeigen bei den 7-tägigen Trockenperioden nur schwache oder negative Trends. Bei den 11-tägigen Trockenperioden gilt dies nur für das Frühjahr und den Herbst, im Winter sind die Trends im Norden überwiegend positiv, im Süden negativ. Betrachtet man die Länge der längsten Trockenperioden, so nimmt diese im Sommer zu, im Frühjahr und im Gesamtjahr jedoch ab. Im Herbst ist das Bild uneinheitlich; dies kann aber auch daran liegen, dass lange sommerliche Trockenperioden in den Herbst hineinreichen und dann dort gezählt werden. Ein weiterer Aspekt ist die Analyse der Anzahl und Länge bestimmter Witterungsabschnitte (Clusteranalyse), die durch relativ hohe oder tiefe Temperatur bzw. relativ wenig bzw. viel Niederschlag definiert sind. So können beispielsweise Tage mit weniger als 1 mm Niederschlag als Trockencluster bezeichnet werden. Dabei erkennt man im Sommer einen Trend zu mehr Trockenclustern,in Übereinstimmung mit den oben genannten Ergebnissen, in den übrigen Jahreszeiten und im Gesamtjahr jedoch einen Trend zu weniger Trockenclustern. Innerhalb des Sommers ist dieser Trend im August am stärksten, in den übrigen Jahreszeiten im März, Oktober und Dezember. Bei den Clustern von Feuchteereignissen, das heißt Tagen mit relativ viel Niederschlag, ist das Bild umgekehrt. Im Sommer nimmt deren Zahl ab, ansonsten nimmt sie zu. Die stärksten Trends sind dabei wiederum im August (Abnahme) bzw. im März, Oktober und Dezember (jeweils Zunahme) zu erkennen. Alle diese Trends werden im der Regel umso schwächer, je höher die Schranke der Niederschlagsmenge gewählt wird. Bei den Temperaturdaten sind die Trends von Frost- und Eistagen nur im November überwiegend positiv, in allen Wintermonaten (Dezember, Januar und Februar) jedoch fast ausschließlich negativ. Darin spiegelt sich somit der Trend zu höheren Temperaturen wider. Bei den Wärmeclustern ändern sich die Trends mit der Höhe der Schranke. Bei der Schranke von 25°C zeigen der Juli, insbesondere aber der August positive Trends. Bei der 30°C-Schranke bleibt der Augusttrend positiv, der Julitrend wird dagegen negativ. Bei der Schranke von 35°C werden die Augusttrends dann deutlich geringer, während die Julitrends, wenn auch schwächer ausgeprägt, negativ bleiben. Die Trends im Juni sind dagegen insgesamt schwach. Betrachtet man die Signifikanz der Trends, so sind insbesondere die Trends bei hohen Schranken weniger signifikant. Dies gilt für die hohen Niederschlagschranken (20mm, 30mm, 95%-Perzentil, 99%-Perzentil) ebenso wie für die hohen Temperaturschranken (30°C, 35°C). Weiterhin ist die Signifikanz dann niedrig, wenn die Zahl der Cluster im betrachteten Zeitraum klein ist. In Monaten und Jahreszeiten, in denen nur wenige Cluster auftreten, ist der Trend der Zahl der Cluster meist nicht signifikant. Insgesamt zeigen beim Niederschlag die untere Schranke von 1mm sowie die oberen Schranken von 10mm und 90% die signifikantesten Trends. Bei den Temperaturdaten ist das bei den Frosttagen generell, bei den Eistagen im Januar und Februar sowie bei den sommerlichen Clustern mit einer Tagesmaximumtemperatur von über 25°C der Fall (mit zum Teil über 95% bzw. 99% Signifikanz).
Observed global and European spatiotemporal related fields of surface air temperature, mean-sea-level pressure and precipitation are analyzed statistically with respect to their response to external forcing factors such as anthropogenic greenhouse gases, anthropogenic sulfate aerosol, solar variations and explosive volcanism, and known internal climate mechanisms such as the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). As a first step, a principal component analysis (PCA) is applied to the observed spatiotemporal related fields to obtain spatial patterns with linear independent temporal structure. In a second step, the time series of each of the spatial patterns is subject to a stepwise regression analysis in order to separate it into signals of the external forcing factors and internal climate mechanisms as listed above as well as the residuals. Finally a back-transformation leads to the spatiotemporally related patterns of all these signals being intercompared. Two kinds of significance tests are applied to the anthropogenic signals. First, it is tested whether the anthropogenic signal is significant compared with the complete residual variance including natural variability. This test answers the question whether a significant anthropogenic climate change is visible in the observed data. As a second test the anthropogenic signal is tested with respect to the climate noise component only. This test answers the question whether the anthropogenic signal is significant among others in the observed data. Using both tests, regions can be specified where the anthropogenic influence is visible (second test) and regions where the anthropogenic influence has already significantly changed climate (first test).
Diese Arbeit besteht aus zwei Teilen. Im ersten Teil wurde der Einfluss der anthropogen verursachten Erhöhung der atmosphärischen Konzentration von Treibhausgasen auf beobachtete Klimaelemente für die letzten 100 bis 120 Jahre untersucht. Die bodennahe Lufttemperatur wurde in unterschiedlicher räumlicher Auflösung und Abdeckung analysiert: Globales und hemisphärische Mittel, 84 flächengleiche Gebietsmittel globaler Abdeckung und 5°x5°-Gitterpunkte für die europäische Region, für die außerdem der auf Meeresniveau reduzierte Luftdruck und der Niederschlag untersucht wurden. Es wurde ein empirisch-statistischer Ansatz verwendet, der die Datenfelder zunächst in ihre räumlichen und zeitlichen Hauptstrukturen zerlegt (EOF-Zerlegung) und nachfolgend Regressionsbeziehungen zwischen den zeitlichen Hauptstrukturen (Zielgrößen) und den potenziellen Einflussgrößen mittels einer Selektionsstrategie (schrittweise Regression) findet, was zu einer Signaltrennung bezüglich der unterschiedlichen anthropogenen sowie natürlichen Einflüsse führt. Durch eine Abschätzung der Überzufälligkeit der Signal-Rausch-Verhältnisse wurden die Signifikanzen der einzelnen Signale berechnet. Als anthropogene Einflussgrößen wurden neben der logarithmierten Treibhausgaskonzentration (GHG) noch die Konzentration von troposphärischem Sulfat (SUL) aus anthropogenen Quellen verwendet. Die natürlichen Einflussgrößen umfassen Schwankungen der Solarkonstanten (SOL), Strahlungsantrieb explosiver Vulkanausbrüche (VUL), den Southern Oscillation Index (SOI, als Maß für das El-Nino-Phänomen) und den Nord-Atlantik-Oszillations-Index (NAO). In der globalen und den hemisphärischen Mitteltemperaturen dominiert das GHG-Signal. Es unterscheidet sich dabei hochsignifikant vom Zufall und von der natürlichen Variabilität und weist eine mittlere Signalamplitude von etwa 0,5 K auf. Das SUL-Signal ist hier, wie auch in den anderen Datensätzen, unplausibel, was an den fragwürdigen verwendeten Einflüssen liegt, welche die zugrundeliegenden Prozesse nicht hinreichend erfassen. In den räumlich differenzierten Datensätzen ist der zufallsartige Anteil in den Zeitreihen generell höher als in den gemittelten, was die Signifikanzen der GHG-Signale herabsetzt. In Europa ist vor allem im Winter die NAO dominant, was dort zusätzlich den Nachweis des GHG-Signals erschwert. Im europäischen Luftdruck und Niederschlag werden zwar ebenfalls GHG-Signale gefunden, die jedoch aufgrund der hohen Rauschkomponente nur sehr schwach signifikant sind. Des Weiteren ist die Wirkung der anthropogenen Erhöhung der Treibhausgase auf diese Klimaelemente indirekter als bei der Temperatur, wodurch die statistische Ähnlichkeitsbetrachtung hier eventuell auch natürlich verursachte Trendkomponenten irrtümlich als anthropogen selektiert. Im zweiten Teil der Arbeit wurden Witterungseinflüsse auf Ernteerträge in der BRD (West) von 1950-1998 untersucht. Die Ertragsdaten der 21 untersuchten Fruchtarten sind mit ausgeprägten Trends behaftet, die wahrscheinlich zum weitaus überwiegenden Teil durch gewollte Ertragssteigerungen verursacht worden sind. Diese sog. Züchtungsvarianz wurde daher mittels eines Gaußschen Tiefpassfilters von der interannulären Variabilität getrennt, welche Umwelteinflüssen zugeordnet wird. Hierdurch können keine Wirkungen langfristiger Klimatrends auf die Erträge untersucht werden. Als meteorologische Parameter wurden Bundeslandmittel der bodennahen Lufttemperatur und des Niederschlages in monatlicher Auflösung verwendet. Die quadrierten Klima- Zeitreihen sind ein Maß für extreme Anomalien. Durch Bildung von Produkten bzw. Quotienten aus Temperatur und Niederschlag erhält man Zeitreihen, welche die kombinierte Wirkung beider Klimaelemente beschreiben. Die Witterungsabhängigkeiten der Erträge wurden durch Korrelation und Regression (schrittweise Regression) mit den meteorologischen Parametern quantifiziert. Hierbei zeigte sich unter anderem ein negativer Einfluss feucht-warmer April-Anomalien auf Getreide-Erträge. Des Weiteren konnten Ernteeinbrüche verschiedener Fruchtarten mit extrem trocken-heißen Witterungsperioden im Sommer in Verbindung gebracht werden. Korrelationen und Regressionskoeffizienten von quadratischen Einflussreihen sind fast ausschließlich negativ. Somit wirken sich vor allem extreme Anomalien der meteorologischen Parameter ertragsmindernd aus. Mit Hilfe einer Monte-Carlo-Simulation konnte die Überzufälligkeit der durch die meteorologischen Parameter erklärten Varianzen an den Erträgen qualitativ bewertet werden. In etwa 40% der untersuchten Beziehungen ist ein Witterungsein deutlich sichtbar. Des Weiteren ist eine Untersuchung der Veränderungen (Intensität und Häufung) extremer Witterungen, vor allem sommerlicher Hitzeperioden, nötig, um den Klima-Impakt auf deutsche Ernteerträge besser abzuschätzen. Auch ist die Frage noch offen, ob langfristige anthropogene Klimaänderungen, wie sie hier detektiert worden sind, mit Änderungen des Extremwertverhaltens verknüpft sind.
In der hier vorliegenden Diplomarbeit wurde der globale Einfluß des ENSO-Phänomens (El Niño/Southern Oscillation) und des Vulkanismus auf den Luftdruck in Meeresspiegelhöhe sowie auf die Lufttemperatur in Bodennähe untersucht. Weiterhin sollte der Frage nachgegangen werden, ob starke Vulkanausbrüche das ENSO-Phänomen beeinflussen. Hierfür wurden 100-jährige Zeitreihen von Jahres- und saisonalen Mitteln des Southern-Oscillation-Index (SOI), Anomalien der Meeresoberflächentemperatur im tropischen Ostpazifik (SST) sowie der Vulkanismusparameter nach Grieser [17] verwendet. Weiterhin wurde ein globaler, aus 80 flächengleichen Boxen bestehender Datensatz des Luftdrucks in Meeresspiegelhöhe für den Zeitraum 1883 bis 1992 erstellt und ein gleichartiger Boxdatensatz der Luftemperatur in Bodennähe verwendet. Die angewandte Methodik ist eine von Denhard 1996 [11] entwickelte Filtertechnik (Prozeßfilter), mit deren Hilfe sich externe Störungen auf ein dynamisches System analysieren lassen. Es wurde ein methodischer Vergleich zwischen dem Prozeßfilter und der Kreuzspektralanalyse durchgeführt, der aufzeigte, daß bei der hier vorliegenden Fragestellung der Prozeßfilter bessere Ergebnisse liefert. Die Analysen der ENSO-Parameter (SOI, SST) mit den Boxdatensätzen der internen Klimavariablen (Luftdruck und Temperatur) bestätigen die bekannten Wirkungen des ENSO-Phänomens auf das Temperatur- sowie das Luftdruckfeld in Bodennähe bzw. Meeresspiegelhöhe. Für einen entdeckten, im jahreszeitlichen Verlauf unterschiedlichen Einfluß von ENSO auf die Lufttemperatur im tropischen Westpazifik ist dem Autor keine vergleichbare Diskussion aus der Literatur bekannt. In dieser Region wurde im Winter und Frühjahr (jeweils bezogen auf die Nordhemisphäre) eine Erhöhung der Lufttemperatur während El Niño, im Sommer und Herbst dagegen eine Erniedrigung festgestellt. Die Wirkung des Vulkanismus auf den Luftdruck in Meeresspiegelhöhe ist stark von ENSO überlagert. Dieser Effekt wurde in abgeschwächter Form auch bei den, ansonsten klimatologisch interpretierbaren, Korrelationsmustern zwischen den Gebietsmittelreihen der bodennahen Lufttemperatur und dem Vulkanismusparameter festgestellt. Ein ursächliches Einwirken des Vulkanismus auf ENSO konnte im Rahmen dieser Arbeit nicht gefunden werden.
We synthesised observations of total particle number (CN) concentration from 36 sites around the world. We found that annual mean CN concentrations are typically 300–2000 cm -3 in the marine boundary layer and free troposphere (FT) and 1000–10 000 cm -3 in the continental boundary layer (BL). Many sites exhibit pronounced seasonality with summer time concentrations a factor of 2–10 greater than wintertime concentrations. We used these CN observations to evaluate primary and secondary sources of particle number in a global aerosol microphysics model. We found that emissions of primary particles can reasonably reproduce the spatial pattern of observed CN concentration (R2=0.46) but fail to explain the observed seasonal cycle (R2=0.1). The modeled CN concentration in the FT was biased low (normalised mean bias, NMB=& -88%) unless a secondary source of particles was included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB= -25%). Simulated CN concentrations in the continental BL were also biased low (NMB= -74%) unless the number emission of anthropogenic primary particles was increased or a mechanism that results in particle formation in the BL was included. We ran a number of simulations where we included an empirical BL nucleation mechanism either using the activation-type mechanism (nucleation rate, J, proportional to gas-phase sulfuric acid concentration to the power one) or kinetic-type mechanism (J proportional to sulfuric acid to the power two) with a range of nucleation coefficients. We found that the seasonal CN cycle observed at continental BL sites was better simulated by BL particle formation (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). The nucleation constants that resulted in best overall match between model and observed CN concentrations were consistent with values derived in previous studies from detailed case studies at individual sites. In our model, kinetic and activation-type nucleation parameterizations gave similar agreement with observed monthly mean CN concentrations.
We use observations of total particle number concentration at 36 worldwide sites and a global aerosol model to quantify the primary and secondary sources of particle number. We show that emissions of primary particles can reasonably reproduce the spatial pattern of observed condensation nuclei (CN) (R2=0.51) but fail to explain the observed seasonal cycle at many sites (R2=0.1). The modeled CN concentration in the free troposphere is biased low (normalised mean bias, NMB=−88%) unless a secondary source of particles is included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB=−25%). Simulated CN concentrations in the continental boundary layer (BL) are also biased low (NMB=−74%) unless the number emission of anthropogenic primary particles is increased or an empirical BL particle formation mechanism based on sulfuric acid is used. We find that the seasonal CN cycle observed at continental BL sites is better simulated by including a BL particle formation mechanism (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). Using sensitivity tests we derive optimum rate coefficients for this nucleation mechanism, which agree with values derived from detailed case studies at individual sites.
Bei Driehausen, ca. 13 km nordöstlich von Osnabrück, werden saalezeitliche Schmelzwassersande abgebaut, die wegen der Überlagerung durch Grundmoräne als "Vorschüttsande" anzusprechen sind. Die Grundmoräne läßt sich in einen Setztill und einen Ausschmelztill untergliedern. Aus Messungen der Geschiebeeinregelung ergeben sich für den unteren Teil der Grundmoräne Eisbewegungen nach Südwesten und Westen, für den oberen Schubrichtungen nach Süden. Nach dem südschwedisch geprägten Leitgeschiebeinhalt der Grundmoräne scheint es sich hier um den ersten saalezeitlichen Eisvorstoß in NW-Deutschland zu handeln. An der Basis der ca. 10-15 m mächtigen Schmelzwassersande treten wiederum stärker tonige Sedimente und auch Geschiebe auf, die auf eine ältere, vermutlich elsterzeitliche Grundmoräne hinweisen.
High-pressure single-crystal to 20 GPa and powder diffraction measurements to 50 GPa, show that the structure of Pb2SnO4 strongly distorts on compression with an elongation of one axis. A structural phase transition occurs between 10 GPa and 12 GPa, with a change of space group from Pbam to Pnam. The resistivity decreases by more than six orders of magnitude when pressure is increased from ambient conditions to 50 GPa. This insulator-to-semiconductor transition is accompanied by a reversible appearance change from transparent to opaque. Density functional theory-based calculations show that at ambient conditions the channels in the structure host the stereochemically-active Pb 6s2 lone electron pairs. On compression the lone electron pairs form bonds between Pb2+ ions. Also provided is an assignment of irreducible representations to the experimentally observed Raman bands.
We performed an experiment under long-term microgravity conditions aboard the International Space Station (ISS) to obtain information on the energetics and experimental constraints required for the formation of chondrules in the solar nebula by ’nebular lightning’. As a simplified model system, we exposed porous forsterite (Mg2 SiO4) dust particles to high-energetic arc discharges. The characterization of the samples after their return by synchrotron microtomography and scanning electron microscopy revealed that aggregates had formed, consisting of several fused Mg2SiO4 particles. The partial melting and fusing of Mg2SiO4 dust particles under microgravity conditions leads to a strong reduction of their porosity. The experimental outcomes vary strongly in their appearance from small spherical melt-droplets (∅≈90 µm) to bigger and irregularly shaped aggregates (∅≈350 µm). Our results provided new constraints with respect to energetic aspects of chondrule formation and a roadmap for future and more complex experiments on Earth and in microgravity conditions.
Die nachfolgende Dissertation wurde an der Goethe-Universität Frankfurt am Institut für Geowissenschaften (FB 11) in der Arbeitsgruppe Kristallographie und Mineralogie (AG Winkler) verfasst. Die Betreuung der hier durchgeführten Arbeiten erfolgte hauptsächlich durch Prof. B. Winkler in Zusammenarbeit mit Dr. L. Bayarjargal, PD Dr. E. Haussühl und PD Dr. V. Vinograd. Bei dem vorliegenden Manuskript handelt es sich um eine kumulative bzw. publikationsbasierte Dissertation, welche die Forschungsergebnisse verschiedener bereits veröffentlichter wissenschaftlicher Fachartikel zusammenfasst.
Die Arbeit beschreibt verschiedene Synthesen und Untersuchungen an Carbonaten und teilt sich im Wesentlichen in zwei Abschnitte. Zum einen wurden Experimente mit Carbonaten bei Extrembedingungen bzw. unter hohen Drücken und hohen Temperaturen durchgeführt, wie sie auch im Inneren der Erde zu finden sind. Im zweiten Teil wurden Carbonate bei Raumbedingungen synthetisiert und der Einbau von Seltenerdelementen untersucht. Grundsätzlich werden jedoch in beiden Teilen dieser Arbeit die Strukturen und Eigenschaften verschiedener Carbonate und eine mögliche Kationensubstitution bzw. die Synthese isostruktureller Verbindungen erforscht.
Die Ergebnisse zur Sedimentologie, Taphonomie und Paläoökologie der Dinotheriensande des Urrheins in Rheinhessen geben weiteren Aufschluß über die tektonosedimentäre und paläoökologische Entwicklung des Urrheins. Die als Dinotheriensande bekannten Ablagerungen des Urrheins, deren Bildung nach biostratigraphischen Kleinsäugerfunden ins Obermiozän (Vallesium, MN 9, ca. 10,5 - 11 Ma.) gestellt werden, zeichnen sich durch fossile Wirbeltierfragmente teils großer Säugetiere sowie grober Gerölle überwiegend an der Basis, in einigen Bereichen auch aus Grobsand sowie größtenteils aus Fein- bis Mittelsand bestehenden fluviatilen Sedimenten aus. Der im heutigen Raum von Eppelsheim unter einer Ca. 3 m mächtigen Lössschicht liegende ehemalige Flusslauf des Urrheins floß von Worms und Westhofen aus dem Süden kommend entlang einer tektonisch bedingten Schwächezone in Eppelsheim nach Norden über Bermersheim Richtung Wißberg und Sprendlingen weiter nach Bingen. Dabei räumte die anfänglich sehr starke Strömung die durch tektonische Bewegung und eventuelle Verkarstung geschwächten Kalke der Inflata-Schichten (Aquitanium, Unter Miozän) und den Oberen Cerithienschichten (Chattium, oberstes Ober Oligozän bis Aquitanium, Unter Miozän) zu einem Flussbett aus. Die dabei durch die starke Strömung mitgeführten gut gerundeten, max. 170 mm großen Gerölle und Wirbeltierfragmente wurden an der Basis der Dinotheriensande über den abdichtenden Tonen der oligozänen Süßwasserschichten, in Verbindung mit glimmerfreien Grobsanden, abgelagert. Neben den Grobsanden (0,63 - 2 mm) an der Basis zwischen den großen Geröllen bestehen die Dinotheriensande überwiegend aus Feinsand (0,06 - 0,2 mm) und Mittelsand (0,2 - 0,63 mm), teils in gradierter Schichtung. In einigen Bereichen kommen immer wieder auch Grobsande und kleine bis mittelgroße Gerölle bis zum Top vor. Dabei erreichen die aus mehreren Schichtkörpern bestehenden Ablagerungen der Dinotheriensande bei Eppelsheim eine Gesamtmächtigkeit von 6,96 m. Die einzelnen Schichtkörper dieser Ablagerungen zeigen überwiegend Schrägschichtung, wobei die einzelnen Schichtungsblätter tangentiale Schrägschichtung erkennen lassen. Die Auswertung der Vorschüttungsrichtung aus Schrägschichtungsmessungen ergeben für die Hauptrichtung der Paläoströmung über der Basis eine Strömung aus SSE kommend, wobei die Strömung im weiteren Verlauf der Ablagerungen im Grabungsbereich von Eppelsheim von SE bis hin zum Top der Dinotheriensande von SSW kommend wechselt. Dabei lassen sich in den Ablagerungen der Dinotheriensande mit einer Gesamtmächtigkeit von 6,96 m schwerpunktmäßig von der Basis bis zum Top drei Fossilhorizonte erkennen. Hierbei variiert die Höhe des 2. Fossilhorizontes, von der Basis des 1. Fossilhorizontes in den Dinotherie~sandenü ber dem Ton der Süßwasserschichten gemessen, bei Ca. 140 - 150 Cm, sowie die Höhe des 3. Fossilhorizontes bei Ca. 400 - 410 cm. Neben der Anreicherung von fossilen Wirbeltierresten und den großen Geröllen an der Basis befinden sich in den Dinotheriensanden auch bis zu 50 mm große Gerölle, die überwiegend in dem 2. und 3. Fossilhorizont abgelagert wurden. Die Analyse von 10000 unterschiedlichen Geröllen ergab eine Zusammensetzung von gut gerundeten Quarzarten, Quarzite, Sandsteine, Kieselschiefer, Hornsteine, unterschiedliche Variationen von Chalzedon sowie Karneol, Rhyolith und Granit von der Basis bis zum Top der Dinotheriensande. Zwischen den Sanden eingeschaltete große Tonlinsen machen den Eindruck ehemaliger abgebrochener Uferbruchstücke, zumal sie teilweise mit großen Geröllen sedimentiert wurden. Die eigentlichen Sande bestehen aus überwiegend gut bis kantengerundetem Quarzsand, mit einem Glimmer-Anteil von Muskovit, etwas Biotit und im geringem Maße Phlogopit. Das Schwermineralspektrum setzt sich aus Granat, Apatit, Amphibol, Staurolith, Turmalin, Zirkon, Alterit, Hypersthen, Spinell, Siderit, Rutil, Topas, Gips und Augit sowie einem hohen Gehalt an opaken Mineralen zusammen. Die fossilen Wirbeltierfragmente, von Proboscidae, Rhinocerotidae, Equidae, Suidae, Cervidae, Bovidae, Tragulidae, Anthracotheriidae, Tapiroidae, Castoridae, unterschiedliche Arten von Carnivora sowie von Primaten und Insectivora stammend, bestehen zum größten Teil aus deren Zahnen und Zahnfragmenten. Weitere craniale und postcraniale Fragmente kommen gegenüber den Zähnen in geringerem Umfang vor. Fast alle Fragmente sind leicht bis stark abgerollt (Abrollungsgrad). Der größte Teil der Knochenfragmente zeigt ein einheitliches Bruchmuster, welches sich durch eine sägezahnförmige Fraktur mit scharfen Bruchkanten kennzeichnet. Einige Spuren in Form von Oberflächenmarken an den fossilen Knochen und Zähnen zeigen neben Bißspuren von Carnivora auch postmortale Spuren von Insekten und Nagern. Trockenrisse deuten auf eine mehr oder weniger längere Liegezeit der Kadaver bzw. der Skelette, Teilskelette oder vereinzelter Knochen an der Erdoberfläche vor der eigentlichen Sedimentation in den Dinotheriensanden hin. Auffallend finden sich die fossilen Wirbeltierreste in den Dinotheriensanden fast immer in unartikulierter und vereinzelter Fundlage, ausgenommen im Strömungsschatten größerer Objekte, wie zum Beispiel der große Kalkklotz im Grabungsbereich von Eppelsheim. Dabei handelt es sich um eine durchmischte Ansammlung von unartikulierten Wirbeltier-Fragmenten (Voorhies-Gruppen). Seit Beginn des 19. Jahrhunderts kamen die durch Zufall ausgegrabenen fossilen Wirbeltierreste aus den sogenannten Sandkauten Rheinhessens durch Ankauf ins Hessische Landesmuseum von Darmstadt (HLMD) und, neben anderen Instituten im In- und Ausland sowie einigen Privatsammlungen, ins Naturhistorische Museum von Mainz (NHMM). Die seit 1996 jährlich laufenden wissenschaftlichen Grabungen des Forschungsinstituts Senkenberg / Frankfurt a. Main (FIS) und im Anschluss des NHMM in Eppelsheim lieferten zu diesen historischen Sammlungen weitere Funde. Derzeit sind im HLMD 3217, im NHMM 5432 und im FIS 2278 fossile Funde aus den Dinotheriensanden von Rheinhessen inventarisiert (Stand: Frühjahr 2006). Die bei der Auswertung gewonnenen Daten der bestimmbaren, teilbestimmbaren und unbestimmbaren Funde aller drei Museen (HLMD, NHMM U. FIS) lieferten neben den schon erwahnten Daten über Abrollungsgrad, Bruchmuster, Oberflächenmarken und Voorhies- Gruppen, auch die über die orientierten Zähne ermittelbaren Werte der Mindestanzahl von Individuen aus den bekannten Fundorten in Rheinhessen. Über den Abkauungsgrad der Zähne, in Verbindung mit ihrer natürlichen Position, ließ sich das Altersspektrum dieser Individuen erstellen. Daneben wurde die Fossilienfarbe erfasst, mit deren Hilfe man die Funde in den historischen Sammlungen zur nachträglich Bestimmung des Fundhorizontes benutzen kann, da durch postsedimentäre Ausfällungen die Dinotheriensande, inklusive der darin befindlichen Fossilien, von der Basis bis zum Top unterschiedlich gefärbt sind. Schließlich wurde über die durchschnittlichen Gewichtsdaten der rezenten Vertreter der hier zu behandelten Tierarten eine Verteilungsübersicht in den drei bekannten Museen (HLMD, NHMM u. FIS) erstellt.
The evolution and interrelationships of carnivorous squamates (mosasaurs, snakes, monitor lizards, Gila Monsters) are a contentious part of reptile systematics and go to the heart of conflict between morphological and molecular data in inferring evolutionary history. One of the best-preserved fossils in this motley grouping is “Saniwa” feisti Stritzke, 1983, represented by complete skeletons from the early-middle Eocene of Messel, Germany. We re-describe it on the basis of superficial examination, stereoradiography, and high-resolution X-ray computed tomography of new and published specimens. The scalation of the lizard is unique, consisting of small, keeled scales on the head (including a row of enlarged medial supraorbitals) and large, rhomboidal, keeled scales (invested by osteoderms) that covered the rest of the body. Two paired longitudinal rows of enlarged scales ran down the neck. The head was laterally compressed and box-shaped due to the presence of a strong canthal-temporal ridge; the limbs and tail were very long. Notable osteological features include: a toothed, strap-like vomer; septomaxilla with a long posterior process; palpebral with a long posterolateral process; a lacrimal boss and a single lacrimal foramen; a well-developed cultriform process of the parabasisphenoid; two hypoglossal (XII) foramina in addition to the vagus; a lack of resorption pits for replacement teeth; and possibly the presence of more than one wave of developing replacement teeth per locus. There are no osteological modifications suggestive of an intramandibular hinge, but postmortem displacement of the angular-prearticular-surangular complex in multiple specimens suggests that there might have been some degree of mobility in the lower jaw based on soft-tissue modifications. Using phylogenetic analyses on a data-set comprising 473 morphological characters and 46 DNA loci, we infer that a monophyletic Palaeovaranidae Georgalis, 2017, including Eosaniwa Haubold, 1977, lies on the stem of Varanidae Merrem, 1820, basal to various Cretaceous Mongolian taxa. We transfer feisti to the new genus Paranecrosaurus n. gen. Analysis of gut contents reveals only the second known specimen of the cryptozoic lizard Cryptolacerta hassiaca Müller, Hipsley, Head, Kardjilov, Hilger, Wuttke & Reisz, 2011, confirming a diet that was at least partly carnivorous; the preservation of the teeth of C. hassiaca suggests that the gastric physiology of Paranecrosaurus feisti (Stritzke, 1983) n. comb. had high acidity but low enzyme activity. Based on the foregoing and linear discriminant function analysis, we reconstruct P. feisti n. comb., as a powerful, widely roaming, faunivorous-carnivorous stem monitor lizard with a sensitive snout. If the molecular phylogeny of anguimorphs is correct, then many of the features shared by Helodermatidae Gray, 1837 and Varanidae must have arisen convergently, partly associated with diet. In that case, a reconciliation of morphological and molecular data would require the discovery of equally primitive fossils on the helodermatid stem.
The LPJ-GUESS dynamic vegetation model uniquely combines an individual- and patch-based representation of vegetation dynamics with ecosystem biogeochemical cycling from regional to global scales. We present an updated version that includes plant and soil N dynamics, analysing the implications of accounting for C-N interactions on predictions and performance of the model. Stand structural dynamics and allometric scaling of tree growth suggested by global databases of forest stand structure and development were well-reproduced by the model in comparison to an earlier multi-model study. Accounting for N cycle dynamics improved the goodness-of-fit for broadleaved forests. N limitation associated with low N mineralisation rates reduces productivity of cold-climate and dry-climate ecosystems relative to mesic temperate and tropical ecosystems. In a model experiment emulating free-air CO2 enrichment (FACE) treatment for forests globally, N-limitation associated with low N mineralisation rates of colder soils reduces CO2-enhancement of NPP for boreal forests, while some temperate and tropical forests exhibit increased NPP enhancement. Under a business-as-usual future climate and emissions scenario, ecosystem C storage globally was projected to increase by c. 10 %; additional N requirements to match this increasing ecosystem C were within the high N supply limit estimated on stoichiometric grounds in an earlier study. Our results highlight the importance of accounting for C-N interactions not only in studies of global terrestrial C cycling, but to understand underlying mechanisms on local scales and in different regional contexts.
The LPJ-GUESS dynamic vegetation model uniquely combines an individual- and patch-based representation of vegetation dynamics with ecosystem biogeochemical cycling from regional to global scales. We present an updated version that includes plant and soil N dynamics, analysing the implications of accounting for C–N interactions on predictions and performance of the model. Stand structural dynamics and allometric scaling of tree growth suggested by global databases of forest stand structure and development were well reproduced by the model in comparison to an earlier multi-model study. Accounting for N cycle dynamics improved the goodness of fit for broadleaved forests. N limitation associated with low N-mineralisation rates reduces productivity of cold-climate and dry-climate ecosystems relative to mesic temperate and tropical ecosystems. In a model experiment emulating free-air CO2 enrichment (FACE) treatment for forests globally, N limitation associated with low N-mineralisation rates of colder soils reduces CO2 enhancement of net primary production (NPP) for boreal forests, while some temperate and tropical forests exhibit increased NPP enhancement. Under a business-as-usual future climate and emissions scenario, ecosystem C storage globally was projected to increase by ca. 10%; additional N requirements to match this increasing ecosystem C were within the high N supply limit estimated on stoichiometric grounds in an earlier study. Our results highlight the importance of accounting for C–N interactions in studies of global terrestrial N cycling, and as a basis for understanding mechanisms on local scales and in different regional contexts.