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The most frequently used boundary-layer turbulence parameterization in numerical weather prediction (NWP) models are turbulence kinetic energy (TKE) based-based schemes. However, these parameterizations suffer from a potential weakness, namely the strong dependence on an ad-hoc quantity, the so-called turbulence length scale. The physical interpretation of the turbulence length scale is difficult and hence it cannot be directly related to measurements or large eddy simulation (LES) data. Consequently, formulations for the turbulence length scale in basically all TKE schemes are based on simplified assumptions and are model-dependent. A good reference for the independent evaluation of the turbulence length scale expression for NWP modeling is missing. Here we propose a new turbulence length scale diagnostic which can be used in the gray zone of turbulence without modifying the underlying TKE turbulence scheme. The new diagnostic is based on the TKE budget: The core idea is to encapsulate the sum of the molecular dissipation and the cross-scale TKE transfer into an effective dissipation, and associate it with the new turbulence length scale. This effective dissipation can then be calculated as a residuum in the TKE budget equation (for horizontal sub-domains of different sizes) using LES data. Estimation of the scale dependence of the diagnosed turbulence length scale using this novel method is presented for several idealized cases.
Vegetation responds to drought through a complex interplay of plant hydraulic mechanisms, posing challenges for model development and parameterization. We present a mathematical model that describes the dynamics of leaf water-potential over time while considering different strategies by which plant species regulate their water-potentials. The model has two parameters: the parameter λ describing the adjustment of the leaf water potential to changes in soil water potential, and the parameter Δψww describing the typical ‘well-watered’ leaf water potentials at non-stressed (near-zero) levels of soil water potential. Our model was tested and calibrated on 110 time-series datasets containing the leaf- and soil water potentials of 66 species under drought and non-drought conditions. Our model successfully reproduces the measured leaf water potentials over time based on three different regulation strategies under drought. We found that three parameter sets derived from the measurement data reproduced the dynamics of 53% of an drought dataset, and 52% of a control dataset [root mean square error (RMSE) < 0.5 MPa)]. We conclude that, instead of quantifying water-potential-regulation of different plant species by complex modeling approaches, a small set of parameters may be sufficient to describe the water potential regulation behavior for large-scale modeling. Thus, our approach paves the way for a parsimonious representation of the full spectrum of plant hydraulic responses to drought in dynamic vegetation models.
In the nineteenth century, two Neolithic axe-heads were reported from the Michelsberg enclosure system at Kapellenberg. The recent identification of an unusually large tumulus, from which the axe-heads were almost certainly once recovered, reveals that socio-political hierarchisation, linked to the emergence of high-ranking elites in Brittany and the Paris Basin during the fifth millennium cal BC, may have extended into Central Europe.
A realistic simulation of the atmospheric boundary layer (ABL) depends on an accurate representation of the land–atmosphere coupling. Land surface temperature (LST) plays an important role in this context and the assimilation of LST can lead to improved estimates of the boundary layer and its processes. We assimilated synthetic satellite LST retrievals derived from a nature run as truth into a fully coupled, state‐of‐the‐art land–atmosphere numeric weather prediction model. As assimilation system a local ensemble transform Kalman filter was used and the control vector was augmented by the soil temperature and humidity. To evaluate the concept of the augmented control vector, two‐day case‐studies with different control vector settings were conducted for clear‐sky periods in March and August 2017. These experiments with hourly LST assimilation were validated against the nature run and overall, the RMSE of atmospheric and soil temperature of the first‐guess (and analysis) were reduced. The temperature estimate of the ABL was particularly improved during daytime as was the estimate of the soil temperature during the whole diurnal cycle. The best impact of LST assimilation on the soil and the ABL was achieved with the augmented control vector. Through the coupling between the soil and the atmosphere, the assimilation of LST can have a positive impact on the temperature forecast of the ABL even after 15 hr because of the memory of the soil. These encouraging results motivate further work towards the assimilation of real satellite LST retrievals.
Groundwater is the largest source of accessible freshwater with its dynamics having significantly changed due to human withdrawals, and being projected to continue to as a result of climate change. The pumping of groundwater has led to lowered water tables, decreased base flow, and depletion.
Global hydrological models (GHMs) are used to simulate the global freshwater cycle, assessing impacts of changes in climate and human freshwater use. Currently, groundwater is commonly represented by a bucket-like linear storage component in these models. Bucket models, however, cannot provide information on the location of the groundwater table. Due to this limitation, they can only simulate groundwater discharge to surface water bodies but not recharge from surface water to groundwater and calculate no lateral and vertical groundwater flow whatsoever among grid cells. For instance this may lead to an underestimation of groundwater resources in semiarid areas, where groundwater is often replenished by surface water. In order to overcome these limitations it is necessary to replace the linear groundwater model in GHMs with a hydraulic head gradient-based groundwater flow model
This thesis presents the newly developed global groundwater model G3M and its coupling to the GHM WaterGAP spanning over 70,000 lines of newly developed code. Development and validation of the modeling software are discussed along with numerical challenges. Based on the newly developed software, a global natural equilibrium groundwater model is presented showing better agreements with observations than previous models. Groundwater discharge to rivers is found to be the most dominant flow component globally, compared to flows to other surface water bodies and lateral flows. Furthermore, first global maps of the distribution of gaining and losing surface water bodies are displayed.
For the purpose of determining the uncertainty in model outcomes a sensitivity study is conducted with an innovative approach through applying a global sensitivity analysis for a computationally complex model. First global maps of spatially distributed parameter sensitivities are presented. The results at hand indicate that globally simulated hydraulic heads are equally sensitive to hydraulic conductivity, groundwater recharge and surface water body elevation, even though parameter sensitivities do vary regionally.
A high resolution model of New Zealand is developed to further understand the involved uncertainties connected to the spatial resolution of the global model. This thesis finds that a new understanding is necessary how these models can be evaluated and that a simple increase in spatial resolution is not improving the model performance when compared to observations.
Alongside the assessment of the natural equilibrium, the concept of a fully coupled transient model as integrated storage component replacing the former model in the hydrological model WaterGAP is discussed. First results reveal that the model shows reasonable response to seasonal variability although it contains persistent head trends leading to global overestimates of water table depth due to an incomplete coupling. Nonetheless, WaterGAP-G3M is already able to show plausible long term storage trends for areas that are known to be affected by groundwater depletion. In comparison with two established regional models in the Central Valley the coupled model shows a highly promising simulation of storage declines.
Inclusions of breyite (previously known as walstromite-structured CaSiO3) in diamond are usually interpreted as retrogressed CaSiO3 perovskite trapped in the transition zone or the lower mantle. However, the thermodynamic stability field of breyite does not preclude its crystallization together with diamond under upper-mantle conditions (6–10 GPa). The possibility of breyite forming in subducted sedimentary material through the reaction CaCO3 + SiO2 = CaSiO3 + C + O2 was experimentally evaluated in the CaO–SiO2–C–O2 ± H2O system at 6–10 GPa, 900–1500 ∘C and oxygen fugacity 0.5–1.0 log units below the Fe–FeO (IW) buffer. One experimental series was conducted in the anhydrous subsystem and aimed at determining the melting temperature of the aragonite–coesite (or stishovite) assemblage. It was found that melting occurs at a lower temperature (∼1500 ∘C) than the decarbonation reaction, which indicates that breyite cannot be formed from aragonite and silica under anhydrous conditions and an oxygen fugacity above IW – 1. In the second experimental series, we investigated partial melting of an aragonite–coesite mixture under hydrous conditions at the same pressures and redox conditions. The melting temperature in the presence of water decreased strongly (to 900–1200 ∘C), and the melt had a hydrous silicate composition. The reduction of melt resulted in graphite crystallization in equilibrium with titanite-structured CaSi2O5 and breyite at ∼1000 ∘C. The maximum pressure of possible breyite formation is limited by the reaction CaSiO3 + SiO2 = CaSi2O5 at ∼8 GPa. Based on the experimental results, it is concluded that breyite inclusions found in natural diamond may be formed from an aragonite–coesite assemblage or carbonate melt at 6–8 GPa via reduction at high water activity.
Background: Point of care devices for performing targeted coagulation substitution in bleeding patients have become increasingly important in recent years. New on the market is the Quantra® from HemoSonics (LC, Charlottesville, VA, US). It uses sonorheometry, a sonic estimation of elasticity via resonance (SEER), a novel ultrasound-based technology that measures viscoelastic properties of whole blood. Several studies have already shown the comparability with devices already established on the market such as the ROTEM® (TEM International GmbH, Munich, Germany).
Objective: In contrast to existing studies, the planned study will be the first prospective interventional study using the new Quantra® system in a cardiac surgical patient cohort. The aim is to investigate the non-inferiority between an already existing coagulation algorithm, based on ROTEM®/Multiplate®, and a new algorithm based on the Quantra®, for the treatment of coagulopathic cardiac surgical patients.
Methods: The study is divided into two phases. In an initial observation phase, whole blood samples of 20 patients will be analyzed using both ROTEM®/Multiplate® and Quantra® obtained at three defined points of time (prior to surgery, after completion of cardiopulmonary bypass, on arrival in the intensive care unit). The obtained threshold values will be used to create an algorithm for hemotherapy. In a second intervention phase, the new algorithm will be tested against an algorithm used routineously for years at our department for non-inferiority.
Results: The main objective of the examination is the cumulative loss of blood within 24 hours after surgery. Statistical calculations based on literature and in-house data suggest that the new algorithm is not inferior if the difference in cumulative blood loss is < 150ml/24 h.
Conclusions: Because of the comparability of the Quantra® sonorheometry system with ROTEM® rotational thromboelastometric measurement methods, the existing hemotherapy treatment algorithm can be adapted to the Quantra device with a proof of non-inferiority. Clinical Trial: International Registered Report Identifier (IRRID): clinicaltrials.gov: NCT03902275
We apply seismic full waveform inversion to SH‐ and Love‐wave data for investigating the near‐surface lithology at an archaeological site. We evaluate the resolution of the applied full waveform inversion algorithm through ground truthing in the form of an excavation and sediment core studies. Thereby, we investigate the benefits of full waveform inversion in comparison with other established methods of near‐surface prospecting in terms of resolution capabilities and interpretation security. The study is performed in a presumed harbour area of the ancient Thracian city of Ainos. The exemplary target is the source of a linear magnetic anomaly oriented perpendicular to the coast, which was found in a previous magnetic gradiometry survey, suggesting a mole. The SH‐wave full waveform inversion recovered a subsurface SH‐wave velocity model with submeter resolution showing lateral and vertical velocity variation between 40 and 150 m/s. To tame the non‐linearity of the full waveform inversion, a sequential inversion of frequency bands has to be combined with time‐windowing in order to separate the Love wave from the reflected SH wavefield. We compare the full waveform inversion results with multichannel analysis of surface waves, standard seismic reflection imaging, electrical resistivity tomography and electromagnetic induction. It turns out that the respective depth sections are correlated to a certain degree with the full waveform inversion results. However, the structural resolution of the other geophysical methods is significantly lower than for the full waveform inversion. An exception is the reflection seismic imaging, which shows the same resolution as full waveform inversion but can only be interpreted together with the full waveform inversion–based velocity model. An archaeological excavation as well as coring data allows ground truthing and a direct understanding of the geophysical structures. The results show that the target was a sort of near‐surface trench of about 3–4 m width and 0.8 m to 1.0 m depth, filled with silty sediment, which differs from the layered surrounding in colour and composition. The ground truthing revealed that only SH‐wave full waveform inversion and seismic reflection imaging could image the trench and sediment structure with satisfying lateral and depth resolution. We emphasize that the velocity distribution from SH‐wave full waveform inversion agrees closely with the excavated subsurface structures, and that the discovered changes in seismic velocity correlate with changes in the sand content in the respective sediment facies sequences. The study demonstrated that SH‐wave full waveform inversion is capable to image structural and lithological changes in the near subsurface at scales as low as 0.5 m, thus providing the high resolution needed for archaeological and geoarchaeological prospection.
Ongoing climate change is a major threat to biodiversity and impacts on species distributions and abundances are already evident. Heterogenous responses of species due to varying abiotic tolerances and dispersal abilities have the potential to further amplify or ameliorate these impacts through changes in species assemblages. Here we investigate the impacts of climate change on terrestrial bird distributions and, subsequently, on species richness as well as on different aspects of phylogenetic diversity of species assemblages across the globe. We go beyond previous work by disentangling the potential impacts on assemblage phylogenetic diversity of species gains vs. losses under climate change and compare the projected impacts to randomized assemblage changes.
We show that climate change might not only affect species numbers and composition of global species assemblages but could also have profound impacts on assemblage phylogenetic diversity, which, across extensive areas, differ significantly from random changes. Both the projected impacts on phylogenetic diversity and on phylogenetic structure vary greatly across the globe. Projected increases in the evolutionary history contained within species assemblages, associated with either increasing phylogenetic diversification or clustering, are most frequent at high northern latitudes. By contrast, projected declines in evolutionary history, associated with increasing phylogenetic over-dispersion or homogenisation, are projected across all continents.
The projected widespread changes in the phylogenetic structure of species assemblages show that changes in species richness do not fully reflect the potential threat from climate change to ecosystems. Our results indicate that the most severe changes to the phylogenetic diversity and structure of species assemblages are likely to be caused by species range shifts rather than range reductions and extinctions. Our findings highlight the importance of considering diverse measures in climate impact assessments and the value of integrating species-specific responses into assessments of entire community changes.
Aim: Plant life‐forms characterize key morphological strategies that enable large‐scale comparisons of plant communities. This study applies Raunkiær's plant life‐form concept that was developed for temperate climate to a subtropical island flora, in parts, dominated by summer aridity. We quantify how plant life‐form patterns as well as patterns of important plant functional traits (PFTs) relate to important climate and topographic characteristics.
Location: La Palma, Canary Islands.
Taxon: Flora of La Palma.
Methods: We assigned each native plant species a plant life‐form, that is, phanerophyte, chamaephyte, hemicryptophyte, geophyte and therophyte, as well as PFTs (succulence and N‐fixer). We used stacked species distribution models to assess occurrence probability for each species using the Atlantis database (500 m × 500 m grid). We related richness and percentage values for each plant life‐form and PFT to climate and topography.
Results: Plant life‐forms and PFTs showed a clear pattern within geographic but also climate space, while topography had a minor effect. Phanerophytes mainly contributed to the flora in humid areas. Chamaephytes and hemicryptophytes most strongly contributed to the summit scrub flora and, to some degree, also to the arid coastal regions. Geophytes and therophytes were mainly found in dry coastal regions. N‐fixers contributed mainly to warm‐arid and cool‐arid regions, while succulent species were mainly found in arid coastal regions.
Main conclusions: Raunkiær's plant life‐form concept can be comprehensively transferred to a subtropical island flora by adapting to local unfavourable growing conditions, that is, aridity. Using the strong environmental gradients offered by our study island, we identify substantial climate‐driven variation in patterns of plant life‐forms and PFTs that might be used for large‐scale comparisons in macroecological studies. The growth strategies reflected in Raunkiær's plant life‐forms suggest differences in species establishment and coexistence dynamics within different parts of the island's climate space.