bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantifying post-glacial erosion at the Gorner glacier, Switzerland, using OSL and 10Be surface exposure dating.
Authors: Elkadi Joanne , Lehmann Benjamin , King Georgina , Steinemann Olivia , Ivy-Ochs Susan , Christl Marcus , Herman Frédéric
Published: March 2020

Quaternary erosion through glacial and post-glacial processes has left an imprint on Alpine topography. There are few methods capable of resolving these processes on Late glacial to Holocene timescales. The aim of this study is to contribute towards a more detailed understanding of post-glacial erosion across the Central and Western Alps by better constraining the post-glacial erosion history of the Gorner glacier in Zermatt, Switzerland. This is done using a new approach that combines Optically Stimulated Luminescence (OSL) and 10Be cosmogenic nuclide surface exposure dating to invert for post-glacial erosion rates (Lehmann et al., 2019). Both dating methods are influenced by surface erosion but operate on different spatial scales- OSL signals form within the first 1-5 mm of a rock surface (Sohbati et al., 2011) whereas the 10Be signal accumulates within approximately the first 3 m (Lal, 1991). Six bedrock samples, exposed progressively since the Last Glacial Maximum, were collected along a vertical transect spanning an elevation of 641 m. Preliminary results show inheritance in the bottom three samples suggesting multiple advances and retreat. Further results for the post-glacial erosion rates down the transect, and comparison to other glaciers in the Western Alps, will be presented.

References:

Lal, D., 1991. Cosmic ray labelling of erosion surfaces: in situ nuclide production rates and erosion models. Earth and Planetary Science Letters, 104, 424-439.

Lehmann, B et al., 2019. Evaluating post-glacial bedrock erosion and surface exposure duration by coupling in situ optically stimulated luminescence and 10Be dating. Earth Surface Dynamics, 7.

Sohbati, R. et al., 2011. Investigating the resetting of OSL signals in rock surfaces. Geochronometria, 38(3), 249-258.
Using Sun-induced fluorescence and Carbonyl Sulfide flux to assess the response to seasonal heatwave in a citrus orchard
Authors: Cochavi Amnon , Amer Madi , Stern Rafael , Yakir Dan
Published: March 2020

Springtime heatwaves are common phenomena in the Mediterranean region, named ‘Sharav’ or ‘Hamsin’. During these heatwaves, air temperatures (Ta) and vapor pressure demand (VPD) increase rapidly over 3-5 days, followed by a dramatic drop of at least 5℃ in Ta and 1 kPa in VPD back to the pre-event values.

Here, we used our mobile lab in an irrigated lemon orchard in Rehovot, Israel to carry out eddy covariance (EC) flux measurements of net ecosystem exchange of CO2 (NEE), water vapor, and carbonyl sulfide (COS), as well as canopy Sun-induced fluorescence (SIF) together with other spectral indices (NDVI, PRI, NIRv). This was supplemented with leaf-scale measurements of Pulse Amplitude modulated (PAM). Five heatwave events were detected during a two-months measurement campaign. Two other events were defined as intermediate days, with VPD values higher than normal but lower than in the full-scale heatwaves.

During both the heatwave and intermediate days, the COS fluxes (Fcos), far-red SIF, and electron transport rate (ETR), decreased during midday to the same level, compared to the control days. In contrast, NEE responded differentially between the heatwave and intermediate days, with midday values of -5.9±0.9, -3.7±0.7 and -0.69±0.62 µmol m-2s-1 CO2, in the control, intermediate and heatwave days, respectively. No differences were detected in both NDVI and NIRv values. The PRI index, related to energy transfer through the non-photochemical quenching (NPQ) pathway, showed a similar pattern to that of NEE. The recovery of the ecosystem from the heatwave events was rapid and occurred within a day after the end of the events.

The results indicate a link between the far-red SIF and the ETR in the response to the heatwaves. Moreover, the reduction in far-red SIF was negatively associated with the increase in NPQ, which was reflected in both the spectral (PRI) and the PAM (NPQ value) measurements. The observed decrease in Fcos is expected to reflect a decrease in stomatal conductance to a similar extent in the heatwave and intermediate days. However, the lower rate of CO2 assimilation in the full-scale heat wave days suggests that additional factors further decreased its rates beyond that limited by conductance. This can be related to the increased effect of the heat stress on other energy-demanding pathways (e.g. photorespiratory, isoprene production) that can suppress net assimilation in these days.

This work demonstrated that the relation between carbon assimilation and far-red SIF can be complex, and that combining SIF and COS measurements can help partition the effects of heat stress on conductance and other physiological effects.
Seasonal Variability of Mesoscale Instabilities in the Azores Current System
Authors: Bettencourt João , Guedes Soares Carlos
Published: March 2020

The Azores Current-Front system coincides with the northern limit of the subtropical gyre in  the Eastern North Atlantic. The mean zonal jet is positioned south of the Azores archipelago  and extends from west of the mid-atlantic ridge to the Gulf of Cadiz, where it partially  turns south. North of the main jet, a sub-surface counter-current is found, flowing westwards. The associated thermal front separates the warm subtropical waters from the colder subpolar waters. The instantaneous flow in the Azores Current/Front system is characterized by the presence of meandering currents with length scales of 200 km that regularly shed anticyclonic warm water and cyclonic cold water eddies to the north and south of the mean jet axis, respectively, due to vortex stretching and the planetary beta effect. The time scale of eddy shedding is 100-200 days. On the meandering arms of the current, downwelling 
and upwelling cells are found and sharp thermal gradients are formed and a residual poleward heat transport is observed. The instability cycle that originates the mesoscale meanders and the eddies is well-known from quasi-geostrophic and primitive equation models initialized from a basic baroclinic state: a first phase of baroclinic instability feeds on available potential energy to raise eddy kinetic energy levels, that, in a second phase feed the mean kinetic energy by Reynolds stress convergence. The cycle repeats itself as long as the APE reservoir is filled at the end of each cycle.

However, seasonal variability of the zonal jet dynamics has not been addressed before and it can provide valuable insights in to the variations of the Eastern North Atlantic between the subtropical and subpolar gyres. We use a primitive equation regional ocean model of the Eastern Central North Atlantic with realistic climatological wind and thermal forcing to study the yearly cycle of meandering, eddy shedding and restoration of the mean jet in the Azores/Current system. We observe an semi-annual cycle in the jet's kinetic energy with maxima in Summer/Winter and minima in early Spring/Autumn. Potential energy conversion by baroclinic instability occurs throughout the year but is predominant in the first half of the year. The mean kinetic energy draws from the turbulent kinetic energy through Reynolds stress convergence in periods of 50 - 100 days, that are followed by short barotropic instability periods. During Winter, Reynolds stress convergence, and thus mean jet reinforcement from the mesoscale eddy field, occurs along the jet meridional extent, in the top 500 m of the water column, but from Spring to Autumn it is observed only in the southern flank of the mean jet axis.
AtMoDat: Improving the reusability of ATmospheric MOdel DATa with DataCite DOIs paving the path towards FAIR data
Authors: Neumann Daniel , Ganske Anette , Voss Vivien , Kraft Angelina , Höck Heinke , Peters Karsten , Quaas Johannes , Schluenzen Heinke , Thiemann Hannes
Published: March 2020

The generation of high quality research data is expensive. The FAIR principles were established to foster the reuse of such data for the benefit of the scientific community and beyond. Publishing research data with metadata and DataCite DOIs in public repositories makes them findable and accessible (FA of FAIR). However, DOIs and basic metadata do not guarantee the data are actually reusable without discipline-specific knowledge: if data are saved in proprietary or undocumented file formats, if detailed discipline-specific metadata are missing and if quality information on the data and metadata are not provided. In this contribution, we present ongoing work in the AtMoDat project, -a consortium of atmospheric scientists and infrastructure providers, which aims on improving the reusability of atmospheric model data.
  
Consistent standards are necessary to simplify the reuse of research data. Although standardization of file structure and metadata is well established for some subdomains of the earth system modeling community – e.g. CMIP –, several other subdomains are lacking such standardization. Hence, scientists from the Universities of Hamburg and Leipzig and infrastructure operators cooperate in the AtMoDat project in order to advance standardization for model output files in specific subdomains of the atmospheric modeling community. Starting from the demanding CMIP6 standard, the aim is to establish an easy-to-use standard that is at least compliant with the Climate and Forecast (CF) conventions. In parallel, an existing netCDF file convention checker is extended to check for the new standards. This enhanced checker is designed to support the creation of compliant files and thus lower the hurdle for data producers to comply with the new standard. The transfer of this approach to further sub-disciplines of the earth system modeling community will be supported by a best-practice guide and other documentation. A showcase of a standard for the urban atmospheric modeling community will be presented in this session. The standard is based on CF Conventions and adapts several global attributes and controlled vocabularies from the well-established CMIP6 standard.
  
Additionally, the AtMoDat project aims on introducing a generic quality indicator into the DataCite metadata schema to foster further reuse of data. This quality indicator should require a discipline-specific implementation of a quality standard linked to the indicator. We will present the concept of the generic quality indicator in general and in the context of urban atmospheric modeling data. 
Strike-slip fault reactivation in the Western Alps due to Glacial Isostatic Adjustment
Authors: Grosset Juliette , Mazzotti Stéphane , Vernant Philippe , Chéry Jean , Manchuel Kevin
Published: March 2020

The Western Alps represent the zone of highest seismicity density in metropolitan France. The seismicity is mainly located along two NE-SW strike-slip fault systems: the right-lateral Belledonne Fault and the left-lateral Durance Fault. Glacial Isostatic Adjustment (GIA) is one of the most common processes given to explain intraplate seismicity (e.g., Scandinavia, North America) and is also proposed as a cause of present-day deformation in the Alps. In order to test the impact of deglaciation from the Last Glacial Maximum on pre-existing vertical strike-slip faults in the Western Alps (Belledonne and Durance Faults), we use a finite-element approach to model fault reactivation throughout the deglaciation period, from ca. 18 kyr up to today. The models are tuned to fit present-day deformation rates observed by geodesy (uplift rate up to 2 mm/yr and horizontal radial extension). Simplified models (homogeneous icecap and Earth rheology) show that, under optimum conditions, GIA stress perturbations can activate a NE-SW right-lateral strike-slip fault such as the Belledonne Fault, requiring the fault to have been pre-stressed up to near-failure equilibrium before the onset of deglaciation. The maximum effect of GIA is 1.7 meters of right-lateral slip over 20 kyr, with a peak of displacement between 20 and 10 ka. These models indicate that GIA can result in a maximum slip rate of 0.08 mm/yr averaged over the Holocene, in association with earthquakes up to Mw = 7 (if all displacement is taken in one event). These results are consistent with local paleoseismicity and geomorphology evidence on the Durance fault. However, the impact of GIA on the left-lateral Belledonne Fault is poorly constrained by these simple models. Additional models based on realistic Alpine icecap reconstructions and regional rheology structures will also be presented, that allow us to test the specific effects of GIA on Holocene deformation along both the Belledone and Durance Fault systems.
Vulnerability of C stocks in Polylepis forests of the Peruvian Andes under climate change – evidence from laboratory incubations, microbial nutrient constraints and enzyme activities
Authors: Martin Angela , Meyer Nele , Adamczyk Sylwia , Sietiö Outi-Maaria , Kalu Subin , Mganga Kevin , García Bendezu Sady , Karhu Kristiina
Published: March 2020

Soils are the largest stock of terrestrial carbon, the dynamics of soil organic C (SOC) are controlled by microbial physiology, but how it promotes stable SOC and how it would change with warming, remains unknown. The Huascarán National Park (HNP), the largest mass of tropical glaciers in the world, has lost 20-30% of its glacial cover and the temperatures in this biosphere have risen 0.1°C per decade since 1970. However, no information on the HNP soil carbon stocks is available. As managing SOC is important for global warming mitigation, we study the soil C stocks in Polylepis forests of three valleys in the HNP along a temperature gradient relative to elevation (3300 to 4500 m asl), and their vulnerability to decomposition with increasing temperatures and combined labile C and nutrient (N+P) additions.

We found that higher altitude soils have higher C:N:P ratios which indicates that, as expected, soils at high altitudes are nutrient limited. Also, the activities of the N acquiring enzymes: NAGase and leucine-aminopeptidase, C acquiring enzymes: beta-glucosidase, cellobiosidase, beta-xylosidase and phosphatase were positively correlated with altitude, which indicate that N and P availability decreased with altitude across our gradient. This could make high altitude soils vulnerable to C losses, not just due to increased temperatures, but also due to increased rhizosphere priming effects. Climate warming might increase plant growth and belowground C allocation, which in turn could lead to priming due to nutrient mining.

We found no differences across altitudes in microbial biomass (Cmic) measured with the chloroform fumigation extraction method. We are currently analysing microbial community composition (by PLFA’s and DNA based methods). We will present data on microbial CUE of glucose decomposition, and how it is related to soil C/N ratios, nutrient availability and nutrient requirements, and community composition of the microbes. We also aim to test whether higher CUE is related to higher C stabilisation potential in the form of microbial necromass residues (amino sugars), or higher C loss when microbes efficiently growing on labile substrates will also increase the decomposition of more stable SOC (priming).
Solar cycle variations in differential instrumental responses from ground‑based geomagnetic records
Authors: Gilder Stuart , Wack Michael , Kronberg Elena , Prabhu Ameya
Published: March 2020

We developed a new technique based on differences in instrument responses from ground-based magnetic measurements that extracts the frequency content of the magnetic field with periods ranging from 0.1 to 100 seconds. By stacking hourly averages over an entire year, we found that the maximum amplitude of the magnetic field oscillations occurred near solar noon over diurnal periods at all latitudes except in the auroral oval. Seasonal variability was identified only at high latitude. Long-term trends in field oscillations followed the solar cycle, yet the maxima occurred during the declining phase when high-speed streams in the solar wind dominated. A parameter based on solar wind speed and the relative variability of the interplanetary magnetic field correlated robustly with the ground-based measurements. Our findings suggest that turbulence in the solar wind, its interaction at the magnetopause, and its propagation into the magnetosphere stimulate magnetic field fluctuations at the ground on the dayside over a wide frequency range. Our method enables the study of field line oscillations using the publicly available, worldwide database of geomagnetic observatories.
Comparison of the application of the Hough Transform method (characterization of the SON section in seismic spectrograms) at two different sites (VdlS and Ryggfonn) to study the evolution of avalanches.
Authors: Suriñach Emma , Flores-Márquez Elsa Leticia
Published: March 2020

Recently, a method applying the Hough Transform was used to obtain the numerical parameters of the shape of the SON section of the spectrograms  of the seismic signals generated by snow avalanches at the experimental site of Vallée de la Sion (VdlS, Valais, Switzerland) (SFL, Davos). The avalanches were of different size and type (powder-snow, transitional and wet-snow) descending along the same path and recorded at two different locations 690 m of distance between them on the path. This helped us to estimate the evolution of the avalanche speed along the path from the starting zone to the run-out zone. We obtained different spectrogram definition parameters according to the type of avalanche.

We apply the same methodology to the seismic signals generated by avalanches at the Ryggfonn experimental site (NGI, Oslo). The avalanches were dry/mixed and dry/dense and occurred in the period (2004-2008). They were recorded in a site along the path. The instrumental conditions, characteristics of the raw data, and the data processing were like those of VdLS. However, the topographic characteristics of the site were different. At the Ryggfonn site, the distance between the starting zone and the sensor was 1640 m (985 in VdlS) and the vertical drop was 800 m (700 m in VdLS).

We present and compare the results obtained to validate a possible application of the method used to VdlS to other places and topographic conditions.

This research was funded by the CHARMA (CGL2013–40828–R) and the PROMONTEC projects (CGL2017-84720-R) of the Spanish Ministry of Economy, Industry and Competitiveness (MINEICO-FEDER) and RISKNAT group (2014GR/1243).
Autumn warming delays downregulation of photosynthesis and does not increase risk of freezing damage in interior and coastal Douglas-fir seedlings
Authors: Noordermeer Devin , Velasco Vera , Ensminger Ingo
Published: March 2020

In the next several decades, warming in the northern hemisphere will result in asynchronous phasing between the temperature and photoperiod signals that evergreen conifers rely upon for cold hardening during autumn. Our study investigated intraspecific variation in photosynthetic and photoprotective mechanisms in Douglas-fir (Pseudotsuga menziesii) originating from contrasting climates during simulated summer and autumn conditions, as well as how autumn warming affects downregulation of photosynthesis and development of cold hardening. Following growth under long days and summer temperature (LD/ST; 16 h photoperiod; 22 °C/13 °C day/night), Douglas-fir seedlings from two interior and two coastal provenances were acclimated to simulated autumn conditions with short days and either low temperature (SD/LT; 8 h photoperiod; 4 °C/-4 °C day/night) or high temperature (SD/HT; 8 h photoperiod; 19 °C/11 °C day/night). Exposure to low temperature induced increase in size and de-epoxidation of the xanthophyll cycle pigment pool, development of sustained nonphotochemical quenching, and downregulation of photosynthetic activity. SD/HT seedlings exhibited no downregulation of photosynthesis, corresponding with no change in xanthophyll cycle pigment de-epoxidation and no development of sustained nonphotochemical quenching. However, freezing tolerance development for all provenances was not impaired under SD/HT relative to SD/LT. Interior Douglas-fir provenances developed greater freezing tolerance relative to coastal provenances under both temperature treatments. Our findings suggest that short photoperiod alone is insufficient to induce downregulation of photosynthesis in autumn for Douglas-fir. However, this prolonged period of photosynthetic activity does not appear to bear a trade-off of impaired freezing tolerance.
Land take and industrial zones
Authors: Janku Jaroslava , Kozák Josef , Macounová Kristina , Jacko Karel , Marhoul Adéla Marie , Vopravil Jan , Jehlička Jan
Published: March 2020

Currently, we can see a rapid decline of agricultural land, especially for construction purposes. This negative trend is evident across Europe, the Czech Republic is the country with the fastest loss of land in the EU. One reason for the significant loss of agricultural land is building industrial zones is their utilisation of greenfield areas, and their occupying new areas of agricultural land, often the most the most fertile. The analysis deals with the occupied area (the area of a particular industrial zone), the percentage utilization of that industrial zone, the number of employees in the industrial zone, and the land quality expressed by means of the agricultural land protection class. The results of the analysis show the low usability of industrial zones, the large occupation of agricultural land, and the low benefits to the Czech state and Czech citizens. The results also show poor land use policy in relation to soil protection. This work is followed by the project Sustainable management of natural resources with emphasis on non-production and production ability of soil, the results of which will be included in legislation and binding for spatial planning.

Keywords: soil sealing, land take, land use changes, agricultural land management, land agriculture protection, brownfield
Modelling competition for water between tree and crop roots in an agroforestry system
Authors: Heinlein Florian , Duan Xiaohong , Priesack Eckart
Published: March 2020

In times of climate change, many regions of the world suffer from heat waves and drought periods, which can lead to failure of crops. To a certain extent, irrigation can help to overcome these extreme events. However, in a sustainable agricultural system the water and nutrient applications should be minimized in order to avoid the waste of valuable resources.

Another method to use water more efficiently is the introduction of agroforestry systems, e.g. planting tree strips within a field. On the one hand, these tree strips reduce the evapotranspiration of the crop-soil-system due to shading and reduction of wind speed. On the other hand, temperatures tend to be higher near the trees and the tree roots may deplete available water and nutrient resources for crops.

Recently, an agroforestry sub-model has been implemented into the modular model system Expert-N to simultaneously simulate tree and crop growth. In principle, trees and crops are simulated separately at different grid points next to each other. However, the agroforestry sub-model allows for the exchange of water and matter between the different grid points to simulate mutual influences of trees and crops. Up to now the following processes are considered: shading, distribution of dead tree biomass to the crop area, and changed water distribution as tree roots grow into the crop area.

Depending on the simulated tree root length density at the crop grid points, the tree roots can uptake a certain amount of water from neighbouring grid points. If the total water demand of trees and crops cannot be fulfilled, the water uptake at the respective grid point is reduced for both, trees and crops.

Expert-N is used to simulate the plant production and the water cycle within an agroforestry system. The results comprise plant biomasses, leaf area indices, evapotranspiration, and soil water contents. To show the impact of the agroforestry sub-model on the simulation results, the differences between two simulations, which only vary in the activation of the agroforestry sub-model, are presented and discussed.
Integrated field-agent based modelling using the LUE scientific data base
Authors: Schmitz Oliver , de Jong Kor , Karssenberg Derek
Published: March 2020

The heterogeneous nature of environmental systems poses a challenge to researchers constructing environmental models. Many simulation models of integrated systems need to incorporate phenomena that are represented as spatially and temporally continuous fields as well as phenomena that are modelled as spatially and temporally bounded agents. Examples include moving animals (agents) interacting with vegetation (fields) or static water reservoirs (agents) as components of hydrological catchments (fields). However, phenomena bounded in space and time have particular properties mainly because they require representation of multiple (sometimes mobile) objects that each exist in a small subdomain of the space-time domain of interest. Moreover, these subdomains of objects may overlap in space and time such as interleaving branches due to tree crown growth. Efficient storage and access of different types of phenomena requires an approach that integrates representation of fields and objects in a single data model.

We develop the open-source LUE data model that explicitly stores and separates domain information, i.e. where phenomena exist in the space-time domain, and property information, i.e. what attribute value the phenomenon has at a particular space-time location, for a particular object. Notable functionalities are support for multiple spatio-temporal objects, time domains, objects linked to multiple space and time domains, and relations between objects. The design of LUE is based on the conceptual data model of de Bakker (2017) and implemented as a physical data model using HDF5 and C++ (de Jong, 2019). Our LUE data model is part of a new modelling language implemented in Python, allowing for operations accepting both fields and agents as arguments, and therefore resembling and extending the map algebra approach to field-agent modelling.

We present the conceptual and physical data models and illustrate the usage by implementing a spatial agent-based model simulating changes in human nutrition. We thereby consider the interaction between personal demand and supply of healthy food of nearby stores as well as the influence of agent's social network.

References:

de Bakker, M. P., de Jong, K., Schmitz, O., & Karssenberg, D. (2017). Design and demonstration of a data model to integrate agent-based and field-based modelling. Environmental Modelling & Software, 89, 172–189. https://doi.org/10.1016/j.envsoft.2016.11.016

de Jong, K., & Karssenberg, D. (2019). A physical data model for spatio-temporal objects. Environmental Modelling & Software. https://doi.org/10.1016/j.envsoft.2019.104553

LUE source code repository: https://github.com/pcraster/lue/
Characteristics of Hydrogen and Oxygen Isotopes and Water Vapor Sources in Atmospheric Precipitation in Subtropical Monsoon Islands
Authors: Lai Jianhua , Tang Changyuan , Cao Yingjie , Liu Guangli
Published: March 2020

Globally, more than 600 million inhabitants are living in thousands of islands where communities rely on rainwater, shallow groundwater and springs to meet the needs of drinking and economic development. However, the knowledge of the water cycle is still limited in the small islands. Fieldworks were conducted from Oct. 2018 to the end of 2019 to study the seasonal and spatial changes of isotope compositions of rainwater in the Wanshan Island (area = 8.07km2), Zhuhai, Guangdong, China. The results show that the hydrogen and oxygen isotopes in the island precipitation are enriched in the dry season and depleted in the rainy season because of the seasonal changes of the vapor sources and migration paths simulated by the HYSPLIT model. Compared with GMWL, LMWL (δD = 8.077δ18O + 15.202) has almost the same slope and a higher intercept (R2 = 0.976), which is the same as the local meteoric water line Line of Taiwan, Hong Kong, and other islands in the subtropical monsoon region. The d-excess value on the island was low in the summer season and high in the winter season, ranging from 10.49‰ to 17.06‰, which provides more details for changes in moisture sources. Also, hydrogen and oxygen isotopes in the island have a negative correlation with month precipitation, elevation, and distance from the sea. Our results are significant for the understanding of the hydrological processes of small islands in the tropical and subtropical climate.
Estimating soil moisture at various depths from near surface ESA CCI Soil Moisture
Authors: Grillakis Manolis G. , Koutroulis Aristeidis G. , Polykretis Christos , Alexakis Dimitrios D.
Published: March 2020

Soil moisture drought is a natural, reoccurring phenomenon that can affect any part of the land. It consists one of the most challenging problems for the modern agriculture as it directly affects the water, energy and food security nexus. Remote sensed soil moisture products have been proved to be valuable tools for the study of the soil moisture droughts. The European Space Agency (ESA), through the Climate Change Initiative (CCI) is currently providing nearly 4 decades of global satellite observed, fully homogenized soil moisture (SM) data for the uppermost soil layer. This data is valuable as it consists one of the most complete in time and space observed soil moisture dataset available. One of the main limitations that ESA CCI SM exhibits is the limited depth at which the soil moisture is estimated (limited to approximately 5cm of soil). In this work we use the ESA CCI SM data to estimate the Soil Water Index (SWI) at the global scale, which can serve as a soil moisture approximation for different depths. The SWI is a simple index that simulates the infiltration process. It utilizes an infiltration parameter T, which is related to the hydraulic characteristics. In this work, the T parameter is calibrated and validated at point scale based on soil moisture measurements of the International Soil Moisture Network (ISMN) and the FluxNet2015 (Tier 1) datasets. The regionalization of the T parameter at global scale is performed by linking T to physical soil descriptors using multilinear regression. Physical soil descriptors were obtained from the Soil Grids 250m dataset, i.e. bulk density, sand/silt/clay fractions, soil organic carbon and coarse fragments. The result of this operation is an SWI dataset for a series of different depths between 0 and 1m. This dataset can be used for the systematic evaluation of global hydrological models on their ability to simulate the soil water.
Evaluation of simulated climate variability since the Last Glacial using climate models of varying complexity
Authors: Ziegler Elisa , Rehfeld Kira
Published: March 2020

The climate's mean state reflects only part of the changing climate and how it affects everyday lives. Understanding the climate's variability is crucial to provide more reliable simulations and projections, but temporal and spatial variability patterns and how they are related to changes in the mean state remain unclear. Here, we examine changes in variability since the Last Glacial in response to the warming of the global climate by several degrees. The analysis uses simulations from climate models of different complexity: a two-dimensional energy balance model (TransEBM), an earth system model of intermediate complexity (LoveClim), and a general circulation model (HadCM3). We analyse the simulated variability with respect to the different processes and parameterizations included in the different models and compare the temporal and spatial patterns that emerge. Commonalities as well as differences between models and how they relate to the changing mean state show that fast, low complexity models can capture a range of features of a climate variable's development, but also where such reduced descriptions fall short. As such, the results offer implications for the complexity that is needed and sufficient in parameterizations of climatic processes. Furthermore, we envisage that a comparison to paleoclimate archives can provide limits on the temporal and spatial scales that dominate the variability of climate.
The research unit NEROGRAV: first results on stochastic modeling for gravity field determination with real GRACE and GRACE-FO data
Authors: Murböck Michael , Natalia Panafidina , Christoph Dahle , Karl-Hans Neumayer , Frank Flechtner , König Rolf
Published: March 2020

The central hypothesis of the Research Unit (RU) NEROGRAV (New Refined Observations of Climate Change from Spaceborne Gravity Missions), funded for three years by the German Research Foundation DFG, reads: only by concurrently improving and better understanding of sensor data, background models, and processing strategies of satellite gravimetry, the resolution, accuracy, and long-term consistency of mass transport series from satellite gravimetry can be significantly increased; and only in that case the potential of future technological sensor developments can be fully exploited. Two of the individual projects (IPs) within the RU work on stochastic modeling for GRACE and GRACE-FO gravity field determination. TU München and TU Berlin are responsible for IP4 (OSTPAG: optimized space-time parameterization for GRACE and GRACE-FO data analysis), where besides optimal parameterization the focus is on the stochastic modeling of the key observations, i.e. GRACE and GRACE-FO inter-satellite ranging and accelerometer observations, in a simulation (TU München) and real data (TU Berlin) environment. IP5 (ISTORE: improved stochastic modeling in GRACE/GRACE-FO real data processing), which GFZ is responsible for, works on the optimal utilization of the stochastic properties of the main GRACE and GRACE-FO observation types and the main background models.

This presentation gives first insights into the TU Berlin and GFZ results of these two IPs which are both related on stochastic modeling for real data processing based on GFZ GRACE and GRACE-FO RL06 processing. We present the analyses of K-band inter-satellite range observations and corresponding residuals of three test years of GRACE and GRACE-FO real data in the time and frequency domain. Based on the residual analysis we show results of the effects of different filter matrices, which take into account the stochastic properties of the range observations in order to decorrelate them. The stochastic modeling of the background models starts with Monte-Carlo simulations on background model errors of atmospheric and oceanic mass variations. Different representations of variance-covariance matrices of this model information are tested as input for real GRACE data processing and their effect on gravity field determination are analyzed.
Spatial and temporal patterns of freshwater salinity and impacts on irrigation water use constraints globally
Authors: Thorslund Josefin , van Vliet Michelle T.H.
Published: March 2020

Salinization of freshwater resources is a growing water quality issue, which poses challenges for different sectoral water uses. While it is generally recognized that salinity may constrain irrigation water use, our ability to evaluate the severity and extent of the problem has been hampered by a lack of assessments at the global scale. The aim of this study is to (i) quantify spatial and temporal trends in salinization of surface- and groundwaters in irrigated regions globally, and (ii) evaluate its implications for irrigation water use, by considering global salinity guidelines.

To address these aims, we collected and harmonized electrical conductivity (EC) monitoring data between 1980-2018 at both ground- and surface water locations in irrigated areas around the world. We used a suit of data sources including local, regional and global online water quality databases, and data provided by governmental organizations, river basin management commissions and scientific literature. Estimates of irrigated regions and associated groundwater and surface water withdrawal rates for irrigation water use was estimated using global grid-based hydrological outputs of the PCR-GLOBWB model.

Our results show that 23 % and 73 % of all surface water and groundwater stations, respectively, have long-term annual average EC values that exceed FAO guidelines of irrigation water use restrictions (700 µS/cm). Regionally, dryland areas, such as central and western parts of the US, eastern parts of Australia, South Africa and Southern Europe are particularly affected, but also coastal areas of Bangladesh, Florida and Vietnam show elevated EC levels. Regarding temporal variability, groundwater stations generally have low absolute EC variability, but with a majority of stations exceeding irrigation water use guidelines at more than 50 % of their total measurements for all continents except Europe and South America. For surface waters stations, more variability in terms of both exceedance levels and absolute EC was observed across continents, but with increasing EC during low flow periods, suggesting discharge (and seasonality) to be a strong control on surface water salinity. These results are a first step in assessing global impacts of salinity on irrigation water use constraints. Further assessments on salinity trends and its large-scale drivers will be provide necessary information for sustainable irrigation water use and management today and in the future.
HP/HT deformation experiments of garnet-omphacite aggregates – influence of volume fractions on deformation mechanisms.
Authors: Klackl Stefanie , Kraus Katrin , Renner Jörg , Grasemann Bernhard , Rogowitz Anna
Published: March 2020

Forming in oceanic and continental subduction zones during high to ultra-high-pressure metamorphism, eclogites play an important role in convergent settings. To improve our understanding of eclogite deformation behaviour with respect to its phase abundance of omphacite and garnet, synthetic eclogite samples containing 25, 50 and 75% volume fraction of garnet have been deformed in a modified Griggs-type solid-medium apparatus. Deformation conditions were set to a confining pressure of 2.5 GPa, 900 °C and 3*10-6 s-1. Detailed microstructure analysis via optical and electron microscope imaging (SE, BSE and EBSD) served for identification of the dominant active deformation mechanism.
All eclogite samples show a foliation which is defined by a shape preferred orientation (SPO) of omphacite and intercalated foliation sub-parallel garnet aggregates. Another common feature is a weak crystallographic preferred orientation (CPO) of omphacite which is present throughout all samples. In accordance to uniaxial shortening the CPO resembles an s-type texture with a point maximum of [001] axis parallel to the foliation and a maximum of [010] axis perpendicular to the foliation. The stereographic projection of garnet crystallographic orientation is almost distributed randomly. Nevertheless, both phases show an intracrystalline misorientation, indicating activation of crystal plastic processes. With increasing garnet content the grain average misorientation is increasing in both omphacite and garnet crystals. On the other hand, deformation twinning in omphacite is decreasing with increasing garnet content. Further, all samples show indication of brittle deformation of both garnet and omphacite, increasing with increasing garnet content. In samples with a 25% volume fraction of garnet micro-cracks are primarily orientated perpendicular to the foliation, getting more randomly distributed in samples with a 50 and 75% volume fraction of garnet.
In conclusion, all samples show similar microstructures and textures indicating that similar mechanism are active during deformation. However, the overall dominant deformation behaviour is switching from crystal plastic to brittle with increasing garnet content.
Surface Water Management and Modelling in the Sakia El Hamra Hydraulic Basin (Southern Morocco)
Authors: El-alaouy Nafia , Moumni Aicha , Sebbar Badr-eddine , Gouzrou Abdeljalil , Lahrouni Aberrahman
Published: March 2020

Due to its arid to semi-arid climate, Morocco often faces significant intense rainfall periods that can generate flash floods and raging torrents causing serious damage in a very short period of time. In this context, these recent years, the watershed corresponding to the SAKIA EL HAMRA wadi has known devastating downpours and excessive heavy rains that caused severe floods in Laayoune city and its regions.

The watershed of Sakia El Hamra covers an area of 82000 km2, that drains to Sakia El Hamra wadi, a stream of about 447 km long, crosses the basin in its northern part in the East-to-West direction, to discharge into the Atlantic Ocean at the outlet called Foum El Oued. This zone often experiences dangerous torrents of water and violent flash floods, specifically in the northern part of Laayoune city. For example, a flash flood has occurred at the end of October 2016. The peak flow was far in excess of the average (3000 m3/s against 410m3/s). This river flood, lasted for about 10 h, caused damage to the infrastructure and destruction of agricultural lands near Foum El Oued.

The objective of this study is to investigate, through modelling, the hydrological regime of SAKIA EL HAMRA watershed to prevent the floods in the future and improve warning systems. The hydrological parameters of the watershed were determined by WMS software, namely: zone extent, perimeter, slope, basin’s average elevation, Gravelius compactness index, Horton shape index, average altitude, drainage density and concentration time.

Flood flow return was simulated using the Log-normal distribution, using a long time-series of flow and maximum daily and annual precipitation data, recorded between 1985 and 2016, at the Airport station in Laayoune city. The results showed that during flash floods with known flows, water level can reach up to 13 meters, with high flow velocities flooding hundreds of hectares of surrounding plains at the northern part of the city of Laayoune and agricultural lands near Foum El Oued.
The role of spatial and temporal model resolution in a flood event storyline approach in Western Norway
Authors: Schaller Nathalie , Sillmann Jana , Müller Malte , Haarsma Reindert , Hazeleger Wilco , Jahr Hegdahl Trine , Kelder Timo , van den Oord Gijs , Weerts Albrecht , Whan Kirien
Published: March 2020

A physical climate storyline approach is applied to an autumn flood event caused by an atmospheric river in the West Coast of Norway. The aim is to demonstrate the value and challenges of higher spatial and temporal resolution in simulating impacts. The modelling chain used is the same as the one used operationally, to issue flood warnings for example. Its output is therefore familiar to many users, which we expect will facilitate stakeholder engagement. Two different versions of a hydrological model are run to show that on the one hand, the higher spatial resolution between the global and regional model is necessary to realistically simulate the high spatial variability of precipitation in such a mountainous region. On the other hand we also show that the intensity of the peak streamflow is only captured realistically with hourly data. The higher resolution regional atmospheric model is able to simulate the fact that with the passage of an atmospheric river, some valleys receive high amounts of precipitation and others not. However, the coarser resolution global model shows uniform precipitation in the whole region. Translating the event into the future leads to similar results: while in some catchments, a future flood might be 50% larger than a present one, in others no event occurs because the atmospheric river does not hit that catchment.
Aboveground tree growth is a minor and decoupled fraction of boreal forest carbon input
Authors: Pappas Christoforos , Maillet Jason , Rakowski Sharon , Baltzer Jennifer , Barr Alan , Black Andrew , Fatichi Simone , Laroque Colin , Matheny Ashley , Roy Alexandre , Sonnentag Oliver , Zha Tianshan
Published: March 2020

The boreal biome accounts for approximately one third of the terrestrial carbon (C) sink. However, estimates of its individual C pools remain uncertain and are often limited to specific points in time. Here, focusing on the southern edge of the boreal forest in central Canada, we quantified the magnitude and temporal dynamics of C allocation to aboveground tree growth at a mature black spruce (Picea mariana)-dominated forest stand in Saskatchewan. We reconstructed annual total live aboveground tree biomass increment (AGBi) using a biometric approach, i.e., species-specific allometry combined with forest stand characteristics and tree ring widths collected with a C-oriented sampling design. We explored the links between boreal tree growth and ecosystem C input by comparing AGBi with eddy-covariance-derived ecosystem C fluxes from 1999 to 2015. Mean AGBi at the study site was 71 ± 7 g C m–2 (1999–2015), which is only a minor fraction of gross ecosystem production (GEP; i.e., AGBi / GEP ≈ 9 %). Ecosystem C input and AGBi were decoupled, highlighting the potential role of direct sink limitations (temperature, water availability) on boreal tree wood formation. Moreover, C allocation to AGBi remained stable over time, with a temporal trend of near zero (–0.0001 yr–1; p-value=0.775), contrary to significant trends in GEP (+5.72 g C m–2 yr–2; p-value=0.02) and ecosystem C use efficiency (i.e., NPP / GEP; –0.0041 yr–1, p-value=0.007). These findings highlight the importance of belowground tree C investments, together with the substantial contribution of understory, ground cover and soil to the boreal forest C balance. Our quantitative insights into the magnitude and temporal dynamics of aboveground boreal tree C allocation offer additional observational constraints for terrestrial ecosystem models that, to date, are biased in converting C input to biomass, and can guide forest-management strategies for mitigating carbon dioxide emissions.
The processes driving the water budget in the tropical stratosphere
Authors: Dauhut Thibaut , Lee Keun-Ok , Chaboureau Jean-Pierre , Noël Vincent , Haynes Peter
Published: March 2020

The water vapour in the stratosphere is a strong green-house gas. The usual picture makes its abundance depend first on the temperature of the tropical tropopause via saturation, and second on the activity of the scarce but intense troposphere-stratosphere transport by the very deep convection. This study, designed to identify the various processes at play at the regional scale, benefits from the insitu observations during the StratoClim campaign (August 2017) and the 100-m vertical resolution of a cloud-resolving simulation over the whole south Asia (key region for the stratospheric water budget during the boreal summer). With a combination of Eulerian budget and Lagrangian track of the air masses, we show how the three main driving processes compete: the convective injections via overshoots, the turbulent diffusion, and the freeze-drying episodes driven by large-scale gravity waves, and how much they contribute to the stratospheric humidity at different altitudes.