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Hauptanliegen dieser Arbeit ist es, statistische Zusammenhänge zwischen der Nord-Atlantik-Oszillation (NAO) und der bodennahen Lufttemperatur in Europa zu untersuchen. Dazu wurden zunächst die Korrelationskoeffizienten nach Pearson, Kendall, Spearman und die Transinformation berechnet, sowie die zugehörigen Signifikanzen abgeschätzt. Diese Analysen wurden auch zeitlich gleitend durchgeführt, um mögliche Veränderungen im Einfluß der NAO auf die Temperatur nachweisen zu können. Weiterhin wurde mit Hilfe der selektiven Zeitreihenzerlegung nach signifikanten, charakteristischen zeitlichen Strukturen sowohl in der NAO als auch in den Zeitreihen der Lufttemperatur gesucht: Trend, glatte, saisonale, harmonische Komponente und Rauschen. Zweck dieser Untersuchung war es, gegebenenfalls gleichartige zeitliche Strukturen in der NAO und Temperatur zu finden, um den Zusammenhang zwischen NAO und Temperatur näher beschreiben zu können. Die Untersuchungen wurden fur den Zeitraum von 1871 bis 1990 in monatlicher, saisonaler und jährlicher Auflösung auf Basis von Zeitreihen der mittleren monatlichen Lufttemperatur 41 europäischer WMO- (World Meteorological Organization) Stationen, sowie zwei unterschiedlich definierten NAO-Index-Zeitreihen, die ebenfalls in Monatsmitteln vorlagen, durchgeführt. Ergänzend wurde auf einen globalen Datensatz von Temperaturflächenmitteln zuruckgegriffen, um auch aus globaler Sicht Aussagen uber Zusammenhänge zwischen NAO und bodennaher Lufttemperatur zu erhalten. Die Untersuchungen bezogen sich hierbei auf das Zeitintervall von 1892 bis 1994. Der Zusammenhang zwischen den in Europa beobachteten Temperaturen und der NAO ist linearer Natur und vor allem in den Wintermonaten ausgeprägt. Ein maximaler Zusammenhang findet sich im nordeuropäischen Winter mit einer erklärten Varianz um 40%. Ein Vergleich von extrem kalten Wintern mit der NAO hat gezeigt, daß extreme Kältereignisse nur bei einer schwachen NAO (negativer NAO-Index) auftreten. Im Jahresgang findet eine Verschiebung des durch die NAO beeinflußten Gebietes in Ost-West-Richtung statt. Das Minimum des Zusammenhanges besteht im Sommer bei maximaler Ost-Verschiebung. Weiterhin ist der Einfluß der NAO auf die Temperatur stark zonal ausgeprägt. Es besteht ein Nord-Süd-Gefälle von positiver Korrelation im Norden zu negativer im Süden Europas. Zu diesem Ergebnis führte sowohl die Analyse der Europadaten wie des globalen Datensatzes. Der Einfluß der NAO auf die Temperatur ist nicht stationär; seit Beginn dieses Jahrhunderts hat sich dieser zunehmend ostwärts verlagert. Ein signifikanter Trend konnte in den Indexreihen der NAO aber nicht nachgewiesen werden. Signifikante zeitliche Strukturen der NAO konnten im Bereich der niederfrequenten und auch hochfrequenten Variabilität gefunden werden. Die Winter-NAO (mittlerer Indexwert von Dezember bis Februar) zeigt insbesondere einen in den Wintertemperaturen (Temperaturmittel der Monate Dezember bis Februar) gleichartigen niederfrequenten Verlauf, der durch Polynome vierter und fünfter Ordnung beschrieben werden kann. Im Bereich der hochfrequenten Variabilität konnte mit Ausnahme der Sommer- und Herbstdaten in allen Indexreihen der NAO eine harmonische Schwingung mit einer Periode von etwa 7 Jahren detektiert werden. Die gleiche Schwingung findet sich in den Wintertemperaturen West- und Mitteleuropas.
Die öffentliche Klimadebatte scheint sich zu verselbständigen. Abgehoben von den Erkenntnissen der Fachwissenschaftler reden die einen von der "Klimakatastrophe", die uns demnächst mit voller Wucht treffen wird, wenn wir nicht sofort alles ganz anders machen; Panik ist ihnen das rechte Mittel, Aufmerksamkeit zu erregen. Die anderen sehen im "Klimaschwindel" einen Vorwand für Forschungsgelder und zusätzliche Steuerbelastung der Wirtschaft; ihre Strategie ist Verwirrung und Verharmlosung. Mit der Fixierung auf solche Extrempositionen werden wir den Herausforderungen der Zukunft sicherlich nicht gerecht. Höchste Zeit für eine Versachlichung und für einen klärenden Beitrag zum Verwirrspiel "Klima".
Die Genese der Leptinite und Paragneise zwischen Nordrach und Gengenbach im mittleren Schwarzwald
(1990)
Nachdem die Erforschung der anatektischen Prozesse lange Jahre das Bild des metamorphen Schwarzwalds prägte, wurden durch das Erkennen von Niedrigdruck- und Mitteldruck-Faziesserien (BLÜMEL 1983) und durch die lithologische Gliederung (WIMMENAUER 1984) neue Akzente im metamorphen Grundgebirge gesetzt. Im Rahmen des Kontinentalen Tiefbohrprogramms der Bundesrepublik Deutschland (KTB) wurde im Raum Nordrach-Gengenbach eine Leptinit-Paragneis-Wechselfolge kartiert. Vier Einheiten konnten unterschieden werden: (1) homogene Areale aus biotitarmen Leptiniten, (2) homogene Areale aus biotitreichen Leptiniten, (3) Areale aus verschiedenen, psammopelitischen Paragneisen und (4) eine Wechsellagerung im Aufschlussbereich zwischen Paragneisen und biotitarmen Leptiniten. Die ganze Wechselfolge stellt einen metamorphen, vulkano-sedimentären Komplex aus mindestens zwei verschiedenen Rhyolithen, rhyolithischen Tuffen, Tonsteinen, Grauwacken/Arkosen und Tuffiten dar. Die Struktur des Arbeitsgebiets wird durch die Wippersbach-Mulde, einen Bereich entlang des Haigerach-Tals mit Tendenz zu einem hochtemperatur-mylonitischen Gefüge und den Nordracher Granit, der parallel zur Foliation der Metamorphite intrudierte, geprägt. Im Mittelbachtal ist in streichender Verlängerung der Zone Diersburg-Berghaupten eine ca. 200 m breite Störungszone aufgeschlossen, die mehrphasig mylonitisch und kataklastisch überprägt wurde. Die biotitarmen Leptinite bestehen im wesentlichen aus 40 % Quarz und 60 % Feldspat. Sie sind nahezu massig, feinkörnig-ungleichkörnig (0,1 - 1 mm) mit amöboiden Kornformen. Mylonitische Gefüge kommen untergeordnet vor. Ihr Mineralbestand lautet: Quarz, Biotit, Granat, Sillimanit, Cordierit, Spinell, Ilmenit, Rutil. Die ehemaligen Hypersolvus-Feldspäte Mesoperthit und Antiperthit zeigen eine Entwicklungsreihe zu diskreten Plagioklas(An10-20)- und Orthoklas-Körnern. Um Granat ist eine Corona aus Cordierit-Quarz-Symplektit oder hellgrünem Biotit entwickelt. Die biotitreichen Leptinite haben durch den erhöhten Biotit-Gehalt (um 3 %) ein flaseriges Gefüge. Ihnen fehlt Mesoperthit, dafür führen sie reichlich Antiperthit (An20). Monazit ist ein charakteristischer akzessorischer Gemengteil. Die chemische Zusammensetzung der Leptinite entspricht der von Rhyolithen und ist über viele km nahezu konstant. Eine Probe ist stark an Uran verarmt. Die untersuchten Leptinite ähneln nach Auftreten, Chemismus und Metamorphose den Leptiniten von Todtmoos im Südschwarzwald. Die Paragneise werden in Quarz-Feldspat-reiche Meta-Grauwacken/Meta-Arkosen und Cordierit-reiche Meta-Pelite gegliedert. Das Gefüge ist feinkörnig, lagig-flaserig, teilweise mittelkörnig-migmatitisch und selten mylonitisch oder metablastisch. Der Mineralbestand lautet: Quarz, Plagioklas(An30), Antiperthit, Orthoklas, Biotit, Cordierit, Granat, Kyanit, Sillimanit (meist pseudomorph nach Kyanit), Andalusit (kontaktmetamorph), Spinell, Diaspor, Rutil, Graphit, Ilmenit und Sulfide. Die chemischen Analysen der Paragneise wurden mit denen von nicht metamorphen Sedimenten verglichen: die cordieritreichen Paragneise konnten als metamorphe Tongesteine bestimmt werden, die Quarz-Feldspat-reichen Paragneise sind metamorphe Grauwacken oder Arkosen, da sich Grauwacken und Arkosen nach ihrer chemischen Analyse nicht eindeutig unterscheiden lassen. Im Arbeitsgebiet gibt es nur ein kleines Amphibolit-Vorkommen. Es handelt sich um einen Cummingtonit-führenden Amphibolit, bei dem sich noch ein früheres Metamorphose-Stadium unter hohen Drücken nachweisen lässt. Der Strukturzustand der Alkalifeldspäte (Or85) ist lithologieabhängig und liegt zwischen Orthoklas und Maximum Mikroklin. Granat ist nur schwach diffusions-zoniert. Die Ca-reichen Zentren und Ca-armen Ränder der Granate zeigen eine Druckentlastung an. Aus den Biotit-Analysen (TiO2 bis 5,3 Gew.-%) wurde abgeleitet, da die Tschermak-Substitution die AlVI-Variation nicht erklären kann, sondern dass der AlVI-Gehalt in den untersuchten Biotiten wahrscheinlich vom Fe/(Fe+Mg)-Verhältnis des Gesteins abhängt. Cordierit (teilweise Fe-reich) ist meist pinitisiert. Bei einigen Piniten kann nicht ausgeschlossen werden, dass nach NEDELEC & PAQUET (1981) nicht Cordierit sondern eine Schmelze das Edukt war. Grüner und brauner Fe-Mg-Zn-Aluminat-Spinell kommt vorwiegend zusammen mit Cordierit (±Diaspor) als Corona um Kyanit vor. Das ganze Aggregat wird durch eine äußere Plagioklas-Corona vom Rest des Gesteins abgekapselt. Die metamorphe Entwicklung der untersuchten Gesteine beginnt mit einem druckbetonten Stadium (Hochdruck-Granulitfazies bis ?Eklogit-Fazies) und der Paragenese Granat + Kyanit + Hypersolvus-Feldspäte + Quarz ± Biotit. Die Temperatur lässt sich nur recht unsicher zu 700 °C abschätzen. Mit dem jetzt vorliegenden Plagioklas ergibt sich mit dem GPAQ-Thermobarometer, dem GRAIL- und dem GRIPS-Barometer ein Druck um 7-9 kbar, der als gut belegter Mindestdruck interpretiert wird. Falls aber während dieses Stadiums die Ca-reichen Granat-Zentren der biotitarmen Leptinite mit einem Hypersolvus-Alkalifeldspat (3 Mol-% Anorthit-Komponente nach der CIPW-Norm der Gesteinsanalyse) und Kyanit im Gleichgewicht standen, dann ergeben sich deutlich höhere Drücke von 14-19 kbar. Dieses Metamorphose-Stadium lässt sich mit dem geochronologischen 480 Ma-Ereignis (Ordovizium) korrelieren. Darauf folgt ein Druckentlastungs-Zwischenstadium mit der Umwandlung von Kyanit in Sillimanit und der Bildung der Spinell-Coronen um Al2SiO5-Minerale. Den Abschluss der Metamorphose-Entwicklung bildet ein statisches Cordieritisierungs-Stadium (LP-HT-Metamorphose, Cordierit-Kalifeldspat-Paragenese). Es bewirkte das statische Wachstum von reichlich Cordierit in Biotit-Sillimanit-reichen Teilgefügen und um Granat. Die Temperatur lag dabei nach dem Granat-Biotit-, dem Granat-Cordierit- und dem Granat-Ilmenit-Thermometer bei 650±50 °C. Der Druck betrug dabei nach dem GPAQ-Thermobarometer 3±2 kbar. Dieses Metamorphose-Stadium ist im NE des Raums Nordrach-Gengenbach stark ausgeprägt, im SW, wo das frühe, druckbetonte Stadium gut erhalten ist, nur schwach. Das statische Cordieritisierungs-Stadium lässt sich in das Karbon einstufen.
Mit dem mathematischen Werkzeug zur Filterung von Lärmprozessen, die für die Praktizierung der numerischen Wettervorhersage in ihrer Anfangszeit eine große Rolle gespielt hat, wird an den linearisierten Gleichungen für ein barotropes Flachwassermodell im β-Format die Frage behandelt, wie sich der Rossby-förmige Wellenmodus entwickelt, wenn gleichzeitige Trägheitsschwerewellenmoden infolge von veränderlichen filternden Gleichungen unterdrückt werden.
Zunächst werden einige analytische Grundbeziehungen einer lärmfreien Adjustierung von Anfangsfeldern ausgeführt. Dann richtet sich die Untersuchung auf lärmfilternde prognostische Modellgleichungen (Absch. 5, 6, 7). Aus dieser Analysis in Abhängigkeit von der Filterstufe findet man im Vergleich mit der konventionellen synoptisch-skaligen Rossby-Formel, die der Filterstufe Null entspricht, zum Teil erweiterte Wellengeschwindigkeiten der Rossby-förmigen Physik. Dabei treten sogar unerwartete neue Effekte auf, die wohl primär im Langwellenspektrum zählen.
Die Anwendung der WKB-Theorie zur Simulation der schwach nichtlinearen Dynamik von Schwerewellen
(2014)
Es ist schon seit Längerem bekannt, dass Schwerewellen die Zirkulation der mittleren Atmosphäre beeinflussen. Sie werden fast ausschließlich in der Troposphäre durch Prozesse wie Gebirgsüberströmung, Konvektionen, Frontogenese etc. erzeugt. Sie propagieren von ihrem Entstehungsort in der Troposphäre in die höheren Schichten der Atmosphäre und transportieren dabei ihre Energie und ihren Impuls. Unter der Voraussetzung, dass die Energie von Schwerewellen erhalten bleibt und die Dichte der Atmosphäre mit der Höhe exponentiell abnimmt, wächst die Amplitude der Schwerewellen so stark an, dass sie brechen und ihren Impuls in Stratosphäre und Mesosphäre deponieren. Als Folge davon beeinflussen Schwerewellen die großräumige Zirkulation der Atmosphäre und sind damit ein wichtiges Bindeglied, welches die Troposphäre mit anderen Atmosphärenbereichen verbindet. Folglich ist es wichtig, dass die Klima- und Wettermodelle in der Lage sind, die Schwerewellendynamik zu beschreiben. Bedauerlicherweise können diese Modelle nicht das komplette Schwerewellenspektrum auflösen. Somit müssen Schwerewellen in den Modellen parametrisiert werden. Viele Parametrisierungsschemen basieren auf Wentzel-Kramer-Brillouin(WKB)-Theorie. Die WKB-Gleichungen, die sogenannten Strahlengleichungen, beschreiben die räumliche und zeitliche Variation der Welleneigenschaften wie Wellenzahl, Wellenamplitude und Wellenfrequenz entlang der Charakteristiken, welche durch die lokale Gruppengeschwindigkeit vorgegeben sind. Die numerische Modelle, die auf den Strahlengleichungen basieren, werden als Strahlenmodelle bezeichnet. In Strahlenmodellen werden Schwerewellen durch Wellenteilchen dargestellt. Zur Zeit verwenden die Strahlenmodelle stationäre Strahlengleichungen, da die Wechselwirkung eines zeitabhängigen Schwerewellenfeldes mit einem zeit- und ortsabhängigen Hintergrund zu Problemen in Strahlenmodellen führen kann. Die Strahlengleichungen basieren auf der Annahme, dass sich nie zwei Wellenteilchen mit den unterschiedlichen Welleneigenschaften an einer Position befinden können. Wenn an einer Position zwei Wellenteilchen mit den unterschiedlichen Wellenzahlen befinden, entsteht sogenannte Kaustik: ein Punkt im Raum, an dem sich mehrere Charakteristiken kreuzen. Wenn eine Kaustik entsteht, kann die Wellenamplitude nicht mehr bestimmt werden. Ziel der vorliegenden Arbeit ist es mithilfe der WKB-Theorie die Ausbreitung von Schwerewellenpaketen in einer raum- und zeitabhängigen Hintergrundströmung zu beschreiben und ein numerisches Modell zu entwickeln, welches die Schwerewellen parametrisieren und ihre Wechselwirkung mit der raum- und zeitabhängigen Hintergrundströmung beschreiben kann.
Einfachheitshalber wird in dieser Arbeit nur die Wechselwirkung zwischen horizontal periodischen, vertikal lokalisierten Schwerewellenpaketen und der raum- und zeitabhängigen Hintergrundströmung betrachtet.
A suite of diagnostics is applied to in-situ aircraft measurements and one Chemistry-Climate Model (CCM) data to characterize the vertical structure of the Tropical Tropopause Layer (TTL). The diagnostics are based on vertical tracer profiles and relative vertical tracer gradients, using tropopause-referenced coordinates, and tracer-tracer relationships in the tropical Upper Troposphere/Lower Stratosphere (UT/LS).
Observations were obtained during four tropical campaigns performed from 1999 to 2006 with the research aircraft Geophysica and have been compared to the output of the ECHAM5/MESSy CCM. The model vertical resolution in the TTL (~500 m) allows for appropriate comparison with high-resolution aircraft observations and the diagnostics used highlight common TTL features between the model and the observational data.
The analysis of the vertical profiles of water vapour, ozone, and nitrous oxide, in both the observations and the model, shows that concentration mixing ratios exhibit a strong gradient change across the tropical tropopause, due to the role of this latter as a transport barrier and that transition between the tropospheric and stratospheric regimes occurs within a finite layer. The use of relative vertical ozone and carbon monoxide gradients, in addition to the vertical profiles, helps to highlight the region where this transition occurs and allows to give an estimate of its thickness. The analysis of the CO-O3 and H2O-O3 scatter plots and of the Probability Distribution Function (PDF) of the H2O-O3 pair completes this picture as it allows to better distinguish tropospheric and stratospheric regimes that can be identified by their different chemical composition.
The joint analysis and comparison of observed and modelled data allows to state that the model can represent the background TTL structure and its seasonal variability rather accurately. The model estimate of the thickness of the interface region between tropospheric and stratospheric regimes agrees well with average values inferred from observations. On the other hand, the measurements can be influenced by regional scale variability, local transport processes as well as deep convection, that can not be captured by the model.
A suite of diagnostics is applied to in-situ aircraft measurements and one Chemistry-Climate Model (CCM) data to characterize the vertical structure of the Tropical Tropopause Layer (TTL). The diagnostics are based on the vertical tracers profiles, relative vertical tracers gradients, and tracer-tracer relationships in the tropical Upper Troposphere/Lower Stratosphere (UT/LS), using tropopause coordinates.
Observations come from the four tropical campaigns performed from 1998 to 2006 with the research aircraft Geophysica and have been directly compared to the output of the ECHAM5/MESSy CCM. The model vertical resolution in the TTL allows for appropriate comparison with high-resolution aircraft observations and the diagnostics used highlight common TTL features between the model and the observational data.
The analysis of the vertical profiles of water vapour, ozone, and nitrous oxide, in both the observations and the model, shows that concentration mixing ratios exhibit a strong gradient change across the tropical tropopause, due to the role of this latter as a transport barrier and that transition between the tropospheric and stratospheric regimes occurs within a finite layer. The use of relative vertical ozone gradients, in addition to the vertical profiles, helps to highlight the region where this transition occurs and allows to give an estimate of its thickness. The analysis of the CO-O3 and H2O-O3 scatter plots and of the Probability Distribution Function (PDF) of the H2O-O3 pair completes this picture as it allows to better distinguish tropospheric and stratospheric regimes that can be identified, first, by their differing chemical composition.
The joint analysis and comparison of observed and modelled data allows us to evaluate the capability of the model in reproducing the observed vertical structure of the TTL and its variability, and also to assess whether observations from particular regions on a monthly timescale can be representative of the fine scale mean structure of the Tropical Tropopause Layer.
Development of the flash-heating method for measuring melting temperatures in the diamond anvil cell
(2016)
A new ‘laser flash-heating’ method has been developed for measuring melting temperatures above 2000 K in a diamond anvil cell at gigapascals of pressure. It overcomes the general difficulties in detecting an onset of melting in a diamond anvil cell. It also circumvents the notorious experimental difficulties associated with the long heating durations of the CW laser-heating and the short timescales in the pulsed laser-heating and shock-compression experiments.
In this method, the duration of heating a sample is tuned to avoid chemical reactions of the sample with the diamond anvils and the surrounding pressure medium, while maintaining the accuracy of the temperature measurements. The absence of chemical reactions is confirmed by the EDS technique. Melt detection is now unambiguous from the analysis of textures on the surface and in depth of the recovered samples using the SEM and FIBM techniques, respectively. Using this method, the following has been achieved.
1. The melting curve of hcp-Re has been measured to 48 GPa, 4200 K for the first time. It has a significantly steeper slope than those observed for other transition metals like W and Mo with bcc structures. Above 20 GPa, Re becomes the most refractory metal surpassing W.
2. The melting curve of bcc-Mo has been measured to 45 GPa, 3100 K. It agrees with previous melt-slopes approaching zero value with pressure as reported in the LHDAC experiments using ADXRD and visual observation techniques for inferring the onset of melting. Flash-heating experiments at pressures higher than 50 GPa are required to further corroborate the flat melt-slope and resolve the long standing controversy about melting of Mo.
3. The melting curve of bcc-Ta has been measured to 85 GPa, 4300 K. Unlike in previous experiments using ADXRD and visual observation as probes, it has been tightly bracketed with an unambiguous detection of the onset of melting, without any chemical reaction. The present melting curve cannot be reconciled with shock measurements and theoretical predictions, and the precision of measurements calls for a reevaluation of theoretical, shock compression, and other DAC approaches to determine melting at high pressures. A further analysis with TEM technique for investigating the structure of the heated portion below and above melting temperatures of Ta may benefit in resolving various phase transitions predicted to explain the vast discrepancies in the reported melt-slopes.
When extrapolated to one atmosphere pressure, all the measured flashmelting curves agree with the known melting points.
In this work we present the setup and first tests of our new BIO IN detector. This detector is designed to classify atmospheric ice nuclei (IN) for their biological content. Biological material is identified via its auto-fluorescence (intrinsic fluorescence) after irradiation with UV radiation. Ice nuclei are key substances for precipitation development via the Bergeron–Findeisen process. The level of scientific knowledge regarding origin and climatology (temporal and spatial distribution) of IN is very low. Some biological material is known to be active as IN even at relatively high temperatures of up to –2°C (e.g. pseudomonas syringae bacteria). These biological IN could have a strong influence on the formation of clouds and precipitation. We have designed the new BIO IN sensor to analyze the abundance of IN of biological origin. The instrument will be flown on one of the first missions of the new German research aircraft ''HALO'' (High Altitude and LOng Range).
Development of a Bioaerosol single particle detector (BIO IN) for the Fast Ice Nucleus CHamber FINCH
(2010)
In this work we present the setup and first tests of our new BIO IN detector. This detector was constructed to classify atmospheric ice nuclei (IN) for their biological content. It is designed to be coupled to the Fast Ice Nucleus CHamber FINCH. If one particle acts as an ice nucleus, it will be at least partly covered with ice at the end of the development section of the FINCH chamber. The device combines an auto-fluorescence detector and a circular depolarization detector for simultaneous detection of biological material and discrimination between water droplets, ice crystals and non activated large aerosol particles. The excitation of biological material with UV light and analysis of auto-fluorescence is a common principle used for flow cytometry, fluorescence microscopy, spectroscopy and imaging. The detection of auto-fluorescence of airborne single particles demands some more experimental effort. However, expensive commercial sensors are available for special purposes, e.g. size distribution measurements. But these sensors will not fit the specifications needed for the FINCH IN counter (e.g. high sample flow of up 10 LPM). The newly developed -low cost- BIO IN sensor uses a single high-power UV LED for the electronic excitation instead of much more expensive UV lasers. Other key advantages of the new sensor are the low weight, compact size, and the little effect on the aerosol sample, which allows it to be coupled with other instruments for further analysis. The instrument will be flown on one of the first missions of the new German research aircraft "HALO" (High Altitude and LOng range).
A new version of a digital global map of irrigation areas was developed by combining irrigation statistics for 10825 sub-national statistical units and geo-spatial information on the location and extent of irrigation schemes. The map shows the percentage of each 5 arc minute by 5 arc minute cell that was equipped for irrigation around the year 2000. It is thus an important data set for global studies related to water and land use. This paper describes the data set and the mapping methodology and gives, for the first time, an estimate of the map quality at the scale of countries, world regions and the globe. Two indicators of map quality were developed for this purpose, and the map was compared to irrigated areas as derived from two remote sensing based global land cover inventories. We plan to further improve that data set; therefore comments, information and data that might contribute to that effort are highly welcome.
A new version of a digital global map of irrigation areas was developed by combining irrigation statistics for 10 825 sub-national statistical units and geo-spatial information on the location and extent of irrigation schemes. The map shows the percentage of each 5 arc minute by 5 arc minute cell that was equipped for irrigation around the year 2000. It is thus an important data set for global studies related to water and land use. This paper describes the data set and the mapping methodology and gives, for the first time, an estimate of the map quality at the scale of countries, world regions and the globe. Two indicators of map quality were developed for this purpose, and the map was compared to irrigated areas as derived from two remote sensing based global land cover inventories.
Amines are potentially important for atmospheric new particle formation, but their concentrations are usually low with typical mixing ratios in the pptv range or even smaller. Therefore, the demand for highly sensitive gas-phase amine measurements has emerged in the last several years. Nitrate chemical ionization mass spectrometry (CIMS) is routinely used for the measurement of gasphase sulfuric acid in the sub-pptv range. Furthermore, extremely low volatile organic compounds (ELVOCs) can be detected with a nitrate CIMS. In this study we demonstrate that a nitrate CIMS can also be used for the sensitive measurement of dimethylamine (DMA, (CH3/2NH) using the NO3−•(HNO3)1 − 2• (DMA) cluster ion signal. Calibration measurements were made at the CLOUD chamber during two different measurement campaigns. Good linearity between 0 and ~120 pptv of DMA as well as a sub-pptv detection limit of 0.7 pptv for a 10 min integration time are demonstrated at 278K and 38% RH.
Analysis of stratospheric transport from an observational point of view is frequently realized by evaluation of mean age of air values from long-lived trace gases. However, this provides more insight into general transport strength and less into its mechanism. Deriving complete transit time distributions (age spectra) is desirable, but their deduction from direct measurements is difficult and so far primarily achieved by assumptions about dynamics and spectra themselves. This paper introduces a modified version of an inverse method to infer age spectra from mixing ratios of short-lived trace gases. For a full description of transport seasonality the formulation includes an imposed seasonal cycle to gain multimodal spectra. The EMAC model simulation used for a proof of concept features an idealized dataset of 40 radioactive trace gases with different chemical lifetimes as well as 40 chemically inert pulsed trace gases to calculate pulse age spectra. Annual and seasonal mean inverse spectra are compared to pulse spectra including first and second moments as well as the ratio between them to assess the performance on these time scales. Results indicate that the modified inverse age spectra match the annual and seasonal pulse age spectra well on global scale beyond 1.5 years mean age of air. The imposed seasonal cycle emerges as a reliable tool to include transport seasonality in the age spectra. Below 1.5 years mean age of air, tropospheric influence intensifies and breaks the assumption of single entry through the tropical tropopause, leading to inaccurate spectra in particular in the northern hemisphere. The imposed seasonal cycle wrongly prescribes seasonal entry in this lower region and does not lead to a better agreement between inverse and pulse age spectra without further improvement. As the inverse method aims for future implementation on in situ observational data, possible critical factors for this purpose are delineated finally.
Deriving stratospheric age of air spectra using an idealized set of chemically active trace gases
(2019)
Analysis of stratospheric transport from an observational point of view is frequently realized by evaluation of the mean age of air values from long-lived trace gases. However, this provides more insight into general transport strength and less into its mechanism. Deriving complete transit time distributions (age spectra) is desirable, but their deduction from direct measurements is difficult. It is so far primarily based on model work. This paper introduces a modified version of an inverse method to infer age spectra from mixing ratios of short-lived trace gases and investigates its basic principle in an idealized model simulation. For a full description of transport seasonality the method includes an imposed seasonal cycle to gain multimodal spectra. An ECHAM/MESSy Atmospheric Chemistry (EMAC) model simulation is utilized for a general proof of concept of the method and features an idealized dataset of 40 radioactive trace gases with different chemical lifetimes as well as 40 chemically inert pulsed trace gases to calculate pulse age spectra. It is assessed whether the modified inverse method in combination with the seasonal cycle can provide matching age spectra when chemistry is well-known. Annual and seasonal mean inverse spectra are compared to pulse spectra including first and second moments as well as the ratio between them to assess the performance on these timescales. Results indicate that the modified inverse age spectra match the annual and seasonal pulse age spectra well on global scale beyond 1.5 years of mean age of air. The imposed seasonal cycle emerges as a reliable tool to include transport seasonality in the age spectra. Below 1.5 years of mean age of air, tropospheric influence intensifies and breaks the assumption of single entry through the tropical tropopause, leading to inaccurate spectra, in particular in the Northern Hemisphere. The imposed seasonal cycle wrongly prescribes seasonal entry in this lower region and does not lead to a better agreement between inverse and pulse age spectra without further improvement. Tests with a focus on future application to observational data imply that subsets of trace gases with 5 to 10 species are sufficient for deriving well-matching age spectra. These subsets can also compensate for an average uncertainty of up to ±20 % in the knowledge of chemical lifetime if a deviation of circa ±10 % in modal age and amplitude of the resulting spectra is tolerated.
During the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive dataset of all halogen species relevant for the atmospheric budget of total organic bromine has been collected in the West Pacific region using the FALCON aircraft operated by the German Aerospace agency DLR (Deutsches Zentrum für Luft- und Raumfahrt) covering a vertical range from the planetary boundary layer up to the ceiling altitude of the aircraft of 13 km. In total, more than 700 measurements were performed with the newly developed fully-automated in-situ instrument GHOST-MS (Gas cHromatograph for the Observation of Tracers – coupled with a Mass Spectrometer) by the Goethe University of Frankfurt (GUF) and with the onboard whole-air sampler WASP with subsequent ground based state-of-the-art GC/MS analysis by the University of East Anglia (UEA). Both instruments yield good agreement for all major (CHBr3 and CH2Br2) and minor (CHBrCl, CHBrCl2 and CHBr2Cl) VSLS (very short-lived substances), at least at the level of their 2 σ measurement uncertainties. In contrast to the suggestion that the Western Pacific could be a major source region for VSLS (Pyle et al., 2011), we found only slightly enhanced mixing ratios of brominated halogen source gases relative to the levels reported in Montzka et al. (2011) for other tropical regions. A budget for total organic bromine, including all four halons,CH3Br and the VSLS, is derived for the upper troposphere, the input region for the TTL and thus also for the stratosphere, compiled from the SHIVA dataset. With exception of the two minor VSLS CHBrCl2 and CHBr2Cl, excellent agreement with the values reported in Montzka et al. (2011) is found, while being slightly higher than previous studies from our group based on balloon-borne measurements.
Recent analysis of long-term balloon-borne measurements of Antarctic stratospheric condensation nuclei (CN) and temperature combined with global model calculations showed the wide extent of a mid stratospheric layer of new particles. Here the nucleation model SAWNUC is used to derive Antarctic stratospheric gaseous sulfuric acid profiles and to investigate the nucleation process of this CN layer. The sulfuric acid profiles were derived for an altitude range of 18-32 km between July and October by simulating air parcel trajectories that descend inside the polar vortex and calculating the sulfuric acid amount that reproduces the observations. The derived sulfuric acid concentrations (volume mixing ratios) are of the order of magnitude of 104 cm-3 (10-14) in July. In the following months the concentrations increase to about 107 cm-3 (10 exp -11) in October. They depend strongly on the temperature because a given temperature leaves only a small sulfuric acid range to reproduce the observed magnitude of CN. Ion-induced nucleation occurs. However, while it dominates nucleation at higher temperatures it has no significant influence on the nucleation rates at lower temperatures. Preexisting particles significantly reduce nucleation at sulfuric acid mixing ratios below 1 ppt. First estimates of sulfuric acid production rates range from 0.5 to about 500 molecules cm-3 s-1. A production mechanism for gaseous sulfuric acid during the Antarctic winter seems to be necessary to fully explain the observations. The derived sulfuric acid profiles compare well with midlatitude and Arctic sulfuric acid concentrations.
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.
Die vorliegende Diplomarbeit beschäftigt sich mit dem Vergleich des ASTER GDEM und SRTM, zweier kostenlos verfügbarer, digitaler Geländehöhenmodelle mit nahezu globaler Abdeckung. Die Untersuchungsgebiete befinden sich im Kleinwalsertal (Österreich) und in Südhessen (Deutschland). Der Vergleich der Geländehöhendaten erfolgt durch die Ermittlung der Höhenabweichung zu Referenzhöhen, die aus hochauflösenden amtlichen Geländemodellen ermittelt wurden. Die Höhenabweichung wurde zudem für bestimmte geomorphologische Oberflächenformen und Landbedeckungen ermittelt. Des Weiteren werden die Geländehöhendaten auf ihre Eignung für geomorphometrische und hydrologische Analysen bewertet.
Der Paläontologe und das Meer : Eberhard Gischler erforscht das Klimagedächtnis von Korallenriffen
(2018)
Measurements of vertical velocity from vertically pointing Doppler lidars are used to derive the profiles of vertical velocity variance. Observations were taken during the FESSTVaL (Field Experiment on Submesoscale Spatio-Temporal Variability in Lindenberg) campaign during the warm seasons of 2020 and 2021. Normalized by the square of convective velocity scale, the average vertical velocity variance profile follows the universal profile of Lenschow et al. (1980), however, daily profiles still show a high day-to-day variability. We found that moisture transport and the content of moisture in the boundary layer could explain the remaining variability of the normalized vertical velocity variance. The magnitude of the normalized vertical velocity variance is highest on clear-sky days, and decreases as the relative humidity increase and surface latent heat flux decrease in cloud-topped and rainy days. This suggests that moisture content and moisture transport are limiting factors for the intensity of turbulence in the convective boundary layer. We also found that the intensity of turbulence decreases with an increase in boundary layer cloud fraction during FESSTVaL, while the latent heating in the cloud layer was not a relevant source of turbulence in this case. We conclude that a new vertical velocity scale has to be defined that would take into account the moist processes in the convective boundary layer.
Measurements of vertical velocity from vertically pointing Doppler lidars are used to derive the profiles of normalized vertical velocity variance. Observations were taken during the FESSTVaL (Field Experiment on Submesoscale Spatio-Temporal Variability in Lindenberg) campaign during the warm seasons of 2020 and 2021. Normalized by the square of the convective velocity scale, the average vertical velocity variance profile follows the universal profile of Lenschow et al. (1980). However, daily profiles still show a high day-to-day variability. We found that moisture transport and the content of moisture in the boundary layer could explain the remaining variability of the normalized vertical velocity variance. The magnitude of the normalized vertical velocity variance is highest on clear-sky days and decreases as the absolute humidity increases and surface latent heat flux decreases on cloud-topped days. This suggests that moisture content and moisture transport are limiting factors for the intensity of turbulence in the convective boundary layer. We also found that the intensity of turbulence decreases with an increase in the boundary layer cloud fraction during FESSTVaL, while the latent heating in the cloud layer was not a relevant source of turbulence in this case. We conclude that a new vertical velocity scale has to be defined that would take into account the moist processes in the convective boundary layer.
Chlorine and bromine atoms can lead to catalytic destruction of ozone in the stratosphere. Therefore the use and production of ozone depleting substances (ODS) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent Effective Stratospheric Chlorine (EESC) has been adapted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a new formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the “release time distribution”. The improved formulation shows that EESC levels in the year 1980 for the mid latitude lower stratosphere were significantly lower than previously calculated. 1980 marks the year commonly defined as the onset of anthropogenic ozone depletion in the stratosphere. Assuming that the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than currently assumed in this region of the stratosphere. Based on the improved formulation, EESC level at mid-latitudes will reach this landmark only in 2060. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We conclude that, under the assumptions that all other atmospheric parameters like stratospheric dynamics and chemistry are unchanged, the recovery of mid latitude stratospheric ozone would be expected to be delayed by about a 10 years, in a similar way as EESC.
Strain localization in the lithosphere and the formation, evolution, and maintenance of resulting plate boundaries play a crucial role in plate tectonics and thermo‐chemical mantle convection. Previously activated lithospheric deformation zones often appear to maintain a “memory” of weakening, leading to tectonic inheritance within plate reorganizations including the Wilson cycle. Different mechanisms have been proposed to explain such strain localization, but it remains unclear which operates on what spatio‐temporal scales, and how to best incorporate them in large‐scale mantle convection models. Here, we analyze two candidates, (1), grain‐size sensitive rheology and, (2), damage‐style parameterizations of yield, stress which are sometimes used to approximate the former. Grain‐size reduction due to dynamic recrystallization can drive localization in the ductile domain, and grain growth provides a time‐dependent rheological hardening component potentially enabling the preservation of rheological heterogeneities. We compare the dynamic weakening and hardening effects as well as the timescales of strength evolution for a composite rheology including grain‐size dynamics with a pseudo‐plastic rheology including damage‐ (or “strain”‐) dependent weakening. We explore the implications of different proposed grain‐size evolution laws, and test to which extent strain‐dependent rheologies can mimic the weakening and hardening effects of the more complex micro‐physical behavior. Such an analysis helps to better understand the parallels and differences between various strain‐localization modeling approaches used in different tectonics and geodynamics communities. More importantly, our results contribute to efforts to identify the key ingredients of strain‐localization and damage hysteresis within plate tectonics and how to represent those in planetary‐scale modeling.
Highlights
• New fumarole and thermal water data for Askja and Kverkfjöll volcanoes, Iceland.
• Data compared to modelled compositions and fluxes of magmatic gas.
• Fumarole compositions compatible with origin of CO2 and S from degassing intrusions.
• Intrusive magmatic fluxes sufficient to sustain hydrothermal fluxes of CO2 and S in Iceland
• Magma degassing insignificant/minor source of H2O and Cl to Icelandic hydrothermal fluids
Abstract
Mantle volatiles are transported to Earth's crust and surface by basaltic volcanism. During subaerial eruptions, vast amounts of carbon, sulfur and halogens can be released to the atmosphere during a short time-interval, with impacts ranging in scale from the local environment to the global climate. By contrast, passive volatile release at the surface originating from magmatic intrusions is characterized by much lower flux, yet may outsize eruptive volatile quantities over long timescales. Volcanic hydrothermal systems (VHSs) act as conduits for such volatile release from degassing intrusions and can be used to gauge the contribution of intrusive magmatism to global volatile cycles. Here, we present new compositional and isotopic (δD and δ18O-H2O, 3He/4He, δ13C-CO2, Δ33S-δ34S-H2S and SO4) data for thermal waters and fumarole gases from the Askja and Kverkfjöll volcanoes in central Iceland. We use the data together with magma degassing modelling and mass balance calculations to constrain the sources of volatiles in VHSs and to assess the role of intrusive magmatism to the volcanic volatile emission budgets in Iceland.
The CO2/ΣS (10−30), 3He/4He (8.3–10.5 RA; 3He/4He relative to air), δ13C-CO2 (−4.1 to −0.2 ‰) and Δ33S-δ34S-H2S (−0.031 to 0.003 ‰ and −1.5 to +3.6‰) values in high-gas flux fumaroles (CO2 > 10 mmol/mol) are consistent with an intrusive magmatic origin for CO2 and S at Askja and Kverkfjöll. We demonstrate that deep (0.5–5 kbar, equivalent to ∼2–18 km crustal depth) decompression degassing of basaltic intrusions in Iceland results in CO2 and S fluxes of 330–5060 and 6–210 kt/yr, respectively, which is sufficient to account for the estimated CO2 flux of Icelandic VHSs (3365–6730 kt/yr), but not the VHS S flux (220–440 kt/yr). Secondary, crystallization-driven degassing from maturing intrusions and leaching of crustal rocks are suggested as additional sources of S. Only a minor proportion of the mantle flux of Cl is channeled via VHSs whereas the H2O flux remains poorly constrained, because magmatic signals in Icelandic VHSs are masked by a dominant shallow groundwater component of meteoric water origin. These results suggest that the bulk of the mantle CO2 and S flux to the atmosphere in Iceland is supplied by intrusive, not eruptive magmatism, and is largely vented via hydrothermal fields.
Increasing atmospheric CO2 stimulates photosynthesis which can increase net primary production (NPP), but at longer timescales may not necessarily increase plant biomass. Here we analyse the four decade-long CO2-enrichment experiments in woody ecosystems that measured total NPP and biomass. CO2 enrichment increased biomass increment by 1.05 ± 0.26 kg C m−2 over a full decade, a 29.1 ± 11.7% stimulation of biomass gain in these early-secondary-succession temperate ecosystems. This response is predictable by combining the CO2 response of NPP (0.16 ± 0.03 kg C m−2 y−1) and the CO2-independent, linear slope between biomass increment and cumulative NPP (0.55 ± 0.17). An ensemble of terrestrial ecosystem models fail to predict both terms correctly. Allocation to wood was a driver of across-site, and across-model, response variability and together with CO2-independence of biomass retention highlights the value of understanding drivers of wood allocation under ambient conditions to correctly interpret and predict CO2 responses.
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.
Vielleicht hätte sich außerhalb der Fachwissenschaft niemand für das Weltklimaproblem interessiert, wären da nicht zwei brisante, miteinander gekoppelte Fakten: Die Menschheit ist hochgradig von der Gunst des Klimas abhängig. Es kann uns daher nicht gleichgültig sein, was mit unserem Klima geschieht. Und: Die Menschheit ist mehr und mehr dazu übergegangen, das Klima auch selbst zu beeinflussen. Daraus erwächst uns allen eine besondere Verantwortung. ...
Tropische Korallenriffe sind die artenreichsten Ökosysteme im Ozean. Die »tropischen Regenwälder der Meere« beherbergen zirka 800 Korallenarten und mehrere zehntausend Arten aus fast allen bekannten Tierstämmen. Korallenriffe bedecken weltweit eine Fläche von 600.000 Quadratkilometern, das sind 0,17 Prozent der Erdoberfläche. Sie treten als nahe der Küste gelegene Saumriffe, küstenfernere Barriereriffe, ringförmige Atolle und flache Karbonat-Plattformen auf . Der Begriff »Karbonat« weist darauf hin, dass Korallen als Riffbildner ein Skelett aus Kalk haben. Auch Kalkalgen und Weichtiere wie Muscheln und Schnecken sind durch die Bildung von Kalkskeletten und Kalkschalen am Riffaufbau beteiligt. Da tropische Korallenriffe nur in der Nähe der Meeresoberfläche wachsen, können Geowissenschaftler mit Hilfe fossiler Korallenfunde ermitteln, wie sich der Pegel des Meeresspiegels in vergangenen Jahrtausenden entwickelt hat. Auch andere wichtige Klimadaten wie Wassertemperatur, Sonneneinstrahlung und Kohlendioxid-Gehalt der Atmosphäre sind in Korallenriffen »gespeichert«. Frankfurter Geowissenschaftler erschließen diese wichtigen Daten, die weit vor menschliche Messungen zurückreichen, durch systematische Bohrungen in Korallenriffen der Karibik, des Persischen Golfs und der Malediven.
Crustal structure at the western end of the North Anatolian Fault Zone from deep seismic sounding
(2001)
The first deep seismic sounding experiment in Northwestern Anatolia was carried out in October 1991 as part of the "German - Turkish Project on Earthquake Prediction Research" in the Mudurnu area of the North Anatolian Fault Zone. The experiment was a joint enterprise by the Institute of Meteorology and Geophysics of Frankfurt University, the Earthquake Research Institute (ERI) in Ankara, and the Turkish Oil Company (TPAO). Two orthogonal profiles, each 120 km in length with a crossing point near Akyazi, were covered in succession by 30 short period tape recording seismograph stations with 2 km station spacing. 12 shots, with charge sizes between 100 and 250 kg, were fired and 342 seismograms out of 360 were used for evaluation. By coincidence an M b = 4.5 earthquake located below Imroz Island was also recorded and provided additional information on Moho and the sub-Moho velocity. A ray tracing method orginally developed by Weber (1986) was used for travel time inversion. From a compilation of all data two generalized crustal models were derived, one with velocity gradients within the layers and one with constant layer velocities. The latter consists of a sediment cover of about 2 km with V p » 3.6 km/s, an upper crystalline crust down to 13 km with V p » 5.9 km/s, a middle crust down to 25 km depth with V p » 6.5 km/s, a lower crust down to 39 km Moho depth with V p » 7.0 km/s and V p » 8.05 km/s below the Moho. The structure of the individual profiles differs slightly. The thickest sediment cover is reached in the Izmit-Sapanca-trough and in the Akyazi basin. Of particular interest is a step of about 4 km in the lower crust near Lake Sapanca and probably an even larger one in the Moho (derived from the Imroz earthquake data). After the catastrophic earthquake of Izmit on 17 August 1999 this significant heterogeneity in crustal structure appears in a new light with regard to the possible cause of the Izmit earthquake. Heterogeneities in structure are frequently also heterogeneities in strength and stress that impede or even lock rupture. The Izmit earthquake is discussed in relation to a large stepover or jog at the North Anatolian Fault.
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.
We present the prototype of a regional climate system model based on the COSMO-CLM regional climate model coupled with several model components, analyze the performance of the couplings and present a strategy to find an optimum configuration with respect to computational costs and time to solution.
The OASIS3-MCT coupler is used to couple COSMO-CLM with two land surface models (CLM and VEG3D), a regional ocean model for the Mediterranean Sea (NEMO-MED12), two ocean models for the North and Baltic Sea (NEMO-NORDIC and TRIMNP+CICE) and the atmospheric component of an earth system model (MPI-ESM). We present a unified OASIS3-MCT interface which handles all couplings in a similar way, minimizes the model source code modifications and describes the physics and numerics of the couplings. Furthermore, we discuss solutions for specific regional coupling problems like handling of different domains, multiple usage of MCT interpolation library and efficient exchange of 3D fields.
A series of real-case simulations over Europe has been conducted and the computational performance of the couplings has been analyzed. The usage of the LUCIA tool of the OASIS3-MCT coupler enabled separation of the direct costs of: coupling, load imbalance and additional computations. The resulting limits for time to solution and costs are shown and the potential of further improvement of the computational efficiency is summarized for each coupling.
It was found that the OASIS3-MCT coupler keeps the direct coupling costs of communication and horizontal interpolation small in comparison with the costs of the additional computations and load imbalance for all investigated couplings. For the first time this could be demonstrated for an exchange of approximately 450 2D fields per time step necessary for the atmosphere-atmosphere coupling between COSMO-CLM and MPI-ESM.
A procedure for finding an optimum configuration for each of the couplings was developed considering the time to solution and costs of the simulations. The optimum configurations are presented for sequential and concurrent coupling layouts. The procedure applied can be regarded as independent on the specific coupling layout and coupling details.
In dieser Arbeit werden Schmelz- und Anreicherungsprozesse des Erdmantels, sowie Kristallisationsereignisse der Erdkruste zweier ausgewählter Gebiete in Namibia und Spanien mithilfe geochemischer Methoden rekonstruiert und in einen zeitlichen Zusammenhang gebracht. Ein Vergleich der gewonnenen Ergebnisse beider Kompartimente soll dabei weitere Informationen liefern inwieweit Prozesse des Erdmantels und der Erdkruste miteinander verknüpft waren. Insbesondere soll ein weitere Beitrag zur aktuellen Diskussion geliefert werden, bei der sich das sogenannte „pulsed growth“ und „steady accumulation“ Modell gegenüberstehen (siehe Zusammenstellung Pearson et al., 2007). Zudem tragen die neu gewonnenen Daten dazu bei, die regionalen geologischen Gegebenheiten im besonderen Hinblick auf die geotektonische Geschichte besser zu verstehen.
Das Gibeon Kimberlit Feld befindet sich in der tektonischen Einheit des Rehoboth Terranes in Namibia und ist gekennzeichnet von Vulkanismus vor etwa 72.5 Ma (Davies et al., 2001), der Granat Peridotite und krustale Xenolithe mit an die Oberfläche beförderte. Eine klare Einordnung des Rehoboth Terranes in die Gesamtheit des Süd Afrikanischen Plattenverbunds ist noch nicht vollständig geklärt.
Die Südöstliche vulkanische Provinz in Spanien (SEVP) mit besonderem Hinblick auf die Region um Casas de Tallante stellt das zweite Probengebiet für diese Arbeit dar. Vor etwa 2.6 Ma (Bellon et al., 1983) kam es zur Extrusion von alkali-basaltischen Schmelzen, die zahlreiche Spinell / Plagioklas Peridotite mit sich brachten. Tufflagen, sowie die Matrix der Basalte ermöglichen einen Einblick in die untere Kruste der Region.
Untersuchungen der Erdmantelproben aus Namibia auf ihre Haupt- und Spurenelementchemie, sowie Lu-Hf und Sm-Nd Isotopie zeigten, dass zwei verschiedene Manteltypen vorliegen („N“ und „σ“ Typ), die zu einem Zeitpunkt um etwa 850 Ma („N“) und 1.9 Ga („σ“) angereichert wurden. Eine letzte Anreicherung beider Typen fand vermutlich während der Pan–Afrikanischen Orogenese um etwa 450 Ma statt. Die Reinterpretation eines zuvor publizierten Datensatzes (Pearson et al., 2004), suggeriert, dass es zu einer ersten Verarmung der σ Peridotite um etwa 2.9 Ga kam.
Untersuchungen der U-Pb und Hf Isotopie an Zirkonen aus der unteren Kruste des Probengebiets in Namibia ergaben, dass es zur Bildung von juvenilem Krustenmaterial vermutlich bereits im Archaikum kam (wie bereits vorgeschlagen durch z.B. Hoal et al., 1995; Franz et al., 1996), sowie in den Zeiträumen von 2.3 bis 2.7 und 1.5 bis 1.6 Ga, mit jeweils anschließendem krustalem Recycling und Krustenmischung. Eine Übereinstimmung von Mantel- und Krustenevents konnte für die Zeiträume von etwa 1.8, 0.8 - 0.9 Ga und 0.4 – 0.5 Ga gefunden werden. Eine mögliche erste Verarmung des σ Mantels wird bestätigt durch Zirkonalter im Bereich von 2.7 bis 2.9 Ga.
Die Analyse ausgewählter Spinell / Plagioklas Peridotite aus der SEVP, ergaben, dass ein heterogener Mantel mit mindestens 3 verschiedenen Typen vorliegt. Eine Korrelation der Lu-Hf Isotopie von 3 Proben dieses Probensatzes, sowie den Hf Isotopien einer weiteren Probe von Bianchini et al. (2011) suggerieren, dass es eventuell zu einem Verarmungsereignis zu einem Zeitpunkt von etwa 550 Ma kam. Sr Isotopien von Klinopyroxenen und Plagioklasen im Vergleich ergaben, dass die Sr Isotopie der Plagioklase, im Gegensatz zu den Klinopyroxenen, von denen der Alkali Basalte überprägt wurden.
Zirkonanalysen aus Lokalitäten innerhalb der SEVP (U-Pb, Hf) ergaben ein weitreichendes Altersspektrum, beginnend bei etwa 2-3 Ma bis hin ins Archaikum (2.7 bis 2.9 Ga) mit Provenance Ursprung aus Gondwana und dem Arabisch-Nubischen Schild. Die Kombination der U-Pb Altersinformationen mit den entsprechenden Hf Isotopien, zeigten, dass es vermutlich bereits im Archaikum zu juveniler Krustenbildung kam. Zirkone > 100 µm datieren den Zeitpunkt der Eruption der Alkali Basalte mit Altern um etwa 2.6 Ma und Hf Isotopien, die einem leicht verarmten Mantel entsprechen. Ein mögliches Verarmungsereignis im Erdmantel zu einem Zeitpunkt von etwa 550 Ma, ist im Einklang mit Krustenrecycling zu selbigem Zeitpunkt.
Die neugewonnenen Daten dieser Arbeit unterstützten das „pulsed growth“ Modell.
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In the original manuscript, Figs. 7–16 included fonts which were not correctly embedded in the file. As such, unless certain propriety software (ArcGIS) is installed on the viewing platform, the figures will appear corrupted. In this Corrigendum, Figs. 7–16 and their captions are reproduced with the fonts correctly embedded. Please find the correct figures below.
Convective shower characteristics simulated with the convection-permitting climate model COSMO-CLM
(2019)
This paper evaluates convective precipitation as simulated by the convection-permitting climate model (CPM) Consortium for Small-Scale Modeling in climate mode (COSMO-CLM) (with 2.8 km grid-spacing) over Germany in the period 2001–2015. Characteristics of simulated convective precipitation objects like lifetime, area, mean intensity, and total precipitation are compared to characteristics observed by weather radar. For this purpose, a tracking algorithm was applied to simulated and observed precipitation with 5-min temporal resolution. The total amount of convective precipitation is well simulated, with a small overestimation of 2%. However, the simulation underestimates convective activity, represented by the number of convective objects, by 33%. This underestimation is especially pronounced in the lowlands of Northern Germany, whereas the simulation matches observations well in the mountainous areas of Southern Germany. The underestimation of activity is compensated by an overestimation of the simulated lifetime of convective objects. The observed mean intensity, maximum intensity, and area of precipitation objects increase with their lifetime showing the spectrum of convective storms ranging from short-living single-cell storms to long-living organized convection like supercells or squall lines. The CPM is capable of reproducing the lifetime dependence of these characteristics but shows a weaker increase in mean intensity with lifetime resulting in an especially pronounced underestimation (up to 25%) of mean precipitation intensity of long-living, extreme events. This limitation of the CPM is not identifiable by classical evaluation techniques using rain gauges. The simulation can reproduce the general increase of the highest percentiles of cell area, total precipitation, and mean intensity with temperature but fails to reproduce the increase of lifetime. The scaling rates of mean intensity and total precipitation resemble observed rates only in parts of the temperature range. The results suggest that the evaluation of coarse-grained (e.g., hourly) precipitation fields is insufficient for revealing challenges in convection-permitting simulations.
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.
Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods--typically the most diverse fossilised organisms in Cambrian ecosystems--where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah). Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous) in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace.
The total stratospheric organic chlorine and bromine burden was derived from balloon-borne measurements in the tropics (Teresina, Brazil, 5°04´ S, 42°52´ W) in 2005. Whole air samples were collected cryogenically at altitudes between 15 and 34 km. For the first time, we report measurements of a set of 28 chlorinated and brominated substances in the tropical upper troposphere and stratosphere including ten substances with an atmospheric lifetime of less than half a year. The substances were quantified using pre-concentration techniques followed by Gas Chromatography with Mass Spectrometric detection. In the tropical tropopause layer at altitudes between 15 and 17 km we found 1.1–1.4% of the chlorine and 6–8% of the bromine to be present in the form of very short-lived organic compounds. By combining the data with tropospheric reference data and age of air observations the abundances of inorganic chlorine and bromine (Cly and Bry) were derived. At an altitude of 34 km we calculated 3062 ppt of Cly and 17.5 ppt of Bry from the decomposition of both long- and short-lived organic source gases. Furthermore we present indications for the presence of additional organic brominated substances in the tropical upper troposphere and stratosphere.