bluuebunny/crossref_metadata_2025 huggingface dataset:
Key Atmospheric Signatures for Identifying the Source Reservoirs of Volatiles in Uranus and Neptune
Authors: Mousis Olivier , Aguichine Artyom , Atkinson David H. , Atreya Sushil K. , Cavalié Thibault , Lunine Jonathan I. , Mandt Kathy E. , Ronnet Thomas
Published: March 2020

We investigate the enrichment patterns of several delivery scenarios of the volatiles to the atmospheres of ice giants, having in mind that the only well constrained determination made remotely, i.e. the carbon abundance measurement, suggests that their envelopes possess highly supersolar metallicities, i.e. close to two orders of magnitude above that of the PSN. In the framework of the core accretion model, only the delivery of volatiles in solid forms (amorphous ice, clathrates, pure condensates) to these planets can account for the apparent supersolar metallicity of their envelopes. In contrast, because of the inward drift of icy particles through various snowlines, all mechanisms invoking the delivery of volatiles in vapor forms predict subsolar abundances in the envelopes of Uranus and Neptune. Alternatively, even if the gravitational instability mechanism remains questionable in our solar system, it might be consistent with the supersolar metallicities observed in Uranus and Neptune, assuming the two planets suffered subsequent erosion of their H-He envelopes. Because current technologies do not enable entry probes to reach levels deeper than a few dozens of bars in the atmospheres of giant planets, subsequent probe measurements should focus on the determination of the abundances of the noble gases since these latter never condense in the envelopes of Uranus and Neptune and are expected to be well mixed, even in the top layers at the ~1-bar level. Because these species are highly sensitive to the considered mechanism of volatiles delivery, they should be considered in the top priority of the measurements to be made by an ice giant entry probe.
Arctic Sea Ice: Observations and Global Climate Modelling
Authors: Li Juilin , Richardson Mark , Lee Wei-Liang , Jiang Jonathan , Xu Kuan-Man , Wang Yi-Hui , Fetzer Eric , Liu Yinghui , Yu Jia-Yuh , Stephens Graeme
Published: March 2020

Recent Arctic sea ice retreat has been quicker than the projection in most general circulation model (GCM) simulations. Natural factors may have amplified this, but reliable attribution and projection requires accurate representation of relevant physical processes. In the meeting, we will present results indicating robust links between CloudSat-CALIPSO falling ice and Arctic sea ice melting from observations and global climate modelings.  Most current GCMs don’t fully represent falling ice radiative effects (FIREs).  We find that a small set of Coupled Model Intercomparison Project, phase 5 (CMIP5) models that include FIREs tend to show a faster Arctic sea ice retreat. We investigate this using controlled simulation with the CESM1-CAM5 model both in present-day and 1%CO2 scenarios. With FIREs, CESM1-CAM5 simulates more realistic present-day annual and seasonal variations of radiation and skin temperatures and Arctic sea ice coverage and thickness. Over 60—90 °N oceans, simulated radiative flux trends are similar but the current-day state differs substantially due to FIREs. Falling ice reduces downward shortwave and increase downward longwave, resulting in an improved agreement with the satellite-based CERES-EBAF surface dataset. Under 1pctCO2 simulations, including FIREs results in the first occurrence of an “ice free” Arctic (extent < 1×106 km2) in year 64, compared with year 91 otherwise. We propose that the equivalent greenhouse effects from falling ice results in fewer safe spaces in which sea ice can thicken during winter, resulting in a thinner pack whose retreat is more easily triggered by global warming. However, this explanation does not apply across the CMIP5 ensemble members. Our results therefore only apply to one model but we have shown that this can have substantial implications for Arctic sea ice projection. Given that falling ice interaction with radiation in reality, we propose that including FIREs in models is a high priority.
Past warming trend constrains future warming in CMIP6 models
Authors: Stolpe Martin , Tokarska Katarzyna , Sippel Sebastian , Fischer Erich , Smith Christopher , Lehner Flavio , Knutti Reto
Published: March 2020

Future global warming estimates have been similar across past assessments, but several climate models of the latest Sixth Coupled Model Intercomparison Project (CMIP6) simulate much stronger warming, apparently inconsistent with past assessments. Here we show that projected future warming is correlated with the simulated warming trend during recent decades across CMIP5 and CMIP6 models, enabling us to constrain future warming based on consistency with the observed warming. These findings carry important policy-relevant implications: the observationally-constrained CMIP6 median warming in high emissions and ambitious mitigation scenarios is over 16% and 14% lower by 2050 compared to the raw CMIP6 median, respectively, and over 14% and 8% lower by 2090, relative to 1995-2014. Observationally-constrained CMIP6 warming is consistent with previous assessments based on CMIP5 models, and in an ambitious mitigation scenario, the likely range is consistent with reaching the Paris Agreement target.

 

Reference: 

Tokarska, K.B.†, Stolpe, M.B.†, Sippel, S., Fischer, E.M., Smith, C.J., Lehner, F., and Knutti, R. (2020). Past warming trend constrains future warming in CMIP6 models. Science Advances  (accepted).

†equal first authors
Structural geology of large (ancient) rockslides - an indicator for a seismic or climatic origin?
Authors: Lemaire Emilie , Mreyen Anne-Sophie , Havenith Hans-Balder
Published: March 2020

The stability of rock slopes is often guided by the structural geology of the rocks composing the slope. Geological structures, such as ductile folds, discontinuities as well as brittle faults and fractures, are known factors contributing to a decrease in slope stability according to their orientation in space - with respect to the general orientation of the main slope and its (seismo-) tectonic damage history. Additionally, a rock slope may undergo many forms of gravitationallyinduced, erosional and/or weathering-induced destabilisation.

Rock slope failures may be classified and described according to several factors, such as their volume, displacement mechanisms and velocity. In this work, especially deep-seated and very large failures (with a volume of >107 m3) are analyzed with regard to their structural characteristics.

Giant rockslides originate as planar, rotational, wedge, compound, or irregular slope failures. Most of them convert into flow-like rock avalanches during emplacement. Here, we will not detail the evolution of rock slope failures but rather focus on their origin. The main goal is to identify features allowing to distinguish seismic trigger modes from climatic ones, notably on the basis of the source zone rock structures. We will present examples of classical anti-dip slope (and along-strike) rock structures that hint at a seismic origin, but we will also consider a series of mixed structural types, which are more difficult to interprete. This morpho-structural study is supported by numerical modelling results showing that seismic shaking typically induces deeper seated deformation in initially ‘stable’ rockslopes.

For failures only partially triggered by dynamic shaking, these study results could help to identify the seismic factor in slope evolution. Especially in less seismically active mountain regions, such as the Alps and the Carpathian Mountains, these analyses can be used for paleoseismic studies – provided that dating the seismic initiation of mass movement is possible. For instance, we will show that the “Tamins” and the “Fernpass” rockslides in the Alps present structural and morphological features hinting at a partly seismic origin. Furthermore, we present study cases of ancient rockslides in the SE Carpathians (“Balta” and “Eagle’s Lake”), where a pure seismic origin is most probable and currently under discussion (supported by numerical analyses).
Satellite soil moisture improves rainfall just where needed
Authors: Brocca Luca , Camici Stefania , Massari Christian , Ciabatta Luca , Filippucci Paolo , Villarini Gabriele , Tramblay Yves
Published: March 2020

Soil moisture is a fundamental variable in the water and energy cycle and its knowledge in many applications is crucial. In the last decade, some authors have proposed the use of satellite soil moisture for estimating and improving rainfall, doing hydrology backward. From this research idea, several studies have been published and currently preoperational satellite rainfall products exploiting satellite soil moisture products have been made available.

The assessment of such products on a global scale has revealed an important result, i.e., the soil moisture based products perform better than state of the art products exactly over regions in which the data are needed: Africa and South America. However, over these areas the assessment against rain gauge observations is problematic and independent approaches are needed to assess the quality of such products and their potential benefit in hydrological applications. On this basis, the use of the satellite rainfall products as input into rainfall-runoff models, and their indirect assessment through river discharge observations is an alternative and valuable approach for evaluating their quality.

For this study, a newly developed large scale dataset of river discharge observations over 500+ basins throughout Africa has been exploited. Based on such unique dataset, a large scale assessment of multiple near real time satellite rainfall products has been performed: (1) the Early Run version of the Integrated Multi-Satellite Retrievals for GPM (Global Precipitation Measurement), IMERG Early Run, (2) SM2RAIN-ASCAT (https://doi.org/10.5281/zenodo.3405563), and (3) GPM+SM2RAIN (http://doi.org/10.5281/zenodo.3345323). Additionally, gauge-based and reanalysis rainfall products have been considered, i.e., (4) the Global Precipitation Climatology Centre (GPCC), and (5) the latest European Centre for Medium-Range Weather Forecasts reanalysis, ERA5. As rainfall-runoff model, the semi-distributed MISDc (Modello Idrologico Semi-Distribuito in continuo) model has been employed in the period 2007-2018 at daily temporal scale.

First results over a part of the dataset reveal the great value of satellite soil moisture products in improving satellite rainfall estimates for river flow prediction in Africa. Such results highlight the need to exploit such products for operational systems in Africa addressed to the mitigation of the flood risk and water resources management.
Evaluation of scale-aware convection schemes at the kilometer-scale resolution
Authors: Zhang Xu , Bao Jian-Wen , Chen Baode
Published: March 2020

Numerical weather predictions (NWP) models are increasingly run using kilometer-scale horizontal grid spacing at which convection is partially resolved and the use of a subgrid convection parameterization scheme is still required. Traditionally, subgrid deep convection has been represented by mass flux-based convection parameterizations based on the ensemble-mean closure concept. Recently, a great effort has been made to develop scale-aware subgrid convection schemes that can be used in kilometer-scale NWP models. However, direct evaluation of these schemes is rarely done using coarse-grained large-eddy simulation (LES).

In this study, an idealized LES of deep moist convection is performed to assess the performance of three widely-used scale-aware subgrid convection schemes in the Weather Research and Forecast (WRF) model that is run at 3-km horizontal resolution. It is found that the simulations using the three schemes not only differ from each other but also do not converge to the coarse-grained LES, indicating that further investigation is required as to what “scale-awareness” means in theory and practice.
An Assessment of the Impact of Aeolus Doppler Wind Lidar Observations for Use in Numerical Weather Prediction at ECMWF
Authors: Rennie Michael P. , Isaksen Lars
Published: March 2020

The European Space Agency’s Aeolus mission, which was launched in August 2018, provides profiles of horizontal line-of-sight (HLOS) wind observations from a polar orbiting satellite.  The European Centre For Medium-Range Weather Forecasts (ECMWF) began the operational assimilation of Aeolus Level-2B winds on 9 January 2020 in their global NWP (Numerical Weather Prediction) model, 1 year and 4 months after the first Level-2B wind products were produced in near real time via ESA’s ground processing segment.  This achievement was possible because of the production of good data quality, which was met through a close collaboration of all the parties involved within the Aeolus Data Innovation and Science Cluster (DISC) and via the great efforts of ESA, industry and ground processing algorithms pre- and post-launch.
Through the careful assessment of the statistics of differences of the Aeolus winds relative to the ECMWF model, the Level-2B Rayleigh winds were found to have large systematic errors.  The systematic errors were found to be highly correlated with ALADIN’s (Atmospheric Laser Doppler Instrument) primary mirror temperatures, which vary in a complex manner due to the variation in Earthshine and thermal control of the mirror.  The correction of this source of bias in the ground processing is underway, therefore in the meantime a bias correction scheme using the ECMWF model as a reference was developed for successful data assimilation; the scheme will be described.  
We will present the results of the Aeolus NWP impact assessment which led to the decision to go operational.  Aeolus’ second laser (FM-B, available since late June 2019) provides statistically significant positive impact of moderate to large amplitude, of similar magnitude to some other important and well-established observing systems (such as IR radiances, GNNS radio occultation and Atmospheric Motion Vectors).  Observing System Experiments demonstrate reduction of forecast errors in geopotential and vector wind of around 2% in the tropics and 2-3% in the southern hemisphere for short-range and medium range forecasts (up to day 10).  This positive impact is particularly impressive given that Aeolus provides less than 1% of the total number of observations assimilated, showing the value of direct wind observations for global NWP.
Limiting factors for soil microbial growth in climate change simulation treatments in the Subarctic
Authors: Yuan Mingyue , Na Meng , Hicks Lettice , Rousk Johannes
Published: March 2020

Soil microorganisms play a crucial role in the regulation of nutrient cycling, and are thought to be either limited by low nutrient availability, or by labile carbon supplied by nutrient limited plant productivity. It remains unknown how climate change will affect the rate-limiting resources for decomposer microorganisms in the Arctic, rendering feedbacks to climate change highly uncertain. In this study, we focused on the responses of soil microbial community processes to simulated climate change in a subarctic tundra system in Abisko, Sweden, using litter additions to represent arctic greening and inorganic N fertilizer additions to represent a faster nutrient cycling due to arctic warming. We hypothesized that 1) the plant community would shift and plant productivity would increase in response to N fertilization, 2) microbial process rates would be stimulated by both plant litter and fertilizer additions, and 3) the growth limiting factors for decomposer microorganisms would shift toward nutrient limitation in response to higher plant material input, and towards C-limitation in response to N-fertilizer additions.

 

We assessed the responses of the plant community composition (vegetation surveys) and productivity (NDVI), microbial processes (bacterial growth, fungal growth, C and N mineralization) along with an assessment of the limiting factors for fungal and bacterial growth. The growth-limiting factors were determined by full factorial additions of nutrients (C, N, P), with measurement of microbial growth and respiration following brief incubations in the laboratory. We found that plant productivity was ca. 15% higher in the N fertilized plots. However, field-treatments had limited effects on bacterial growth, fungal growth and the fungal-to-bacterial growth ratio in soils. Field-treatments also had no significant effect on the rate of soil C mineralization, but did affect rates of gross N mineralization. Gross N mineralization was twice as high in N fertilized plots compared to the control. In control soils, bacterial growth increased 4-fold in response to C, indicating that bacterial growth was C limited. Bacterial growth remained C limited in soils from all field-treatments. However, in the N fertilized soils, the C limitation was 1.8-times greater than the control, while in soils with litter input, the C limitation was 0.83-times the control, suggesting that the N fertilized soils were moving towards stronger C-limitation and the litter addition soils were becoming less C-limited. The limiting factor for fungal growth was difficult to resolve. We presumed that the competition of fungi with bacteria decreased our resolution to detect the limiting factor. Therefore, factorial nutrient addition were combined with low amount of bacterial specific inhibitors.
Natural halogens buffer tropospheric ozone in a changing climate
Authors: Iglesias-Suarez Fernando , Badia Alba , Fernandez Rafael P. , Cuevas Carlos A. , Kinnison Douglas E. , Tilmes Simone , Lamarque Jean-François , Long Mathew C. , Hossaini Ryan , Saiz-Lopez Alfonso
Published: March 2020

Reactive atmospheric halogens destroy tropospheric ozone (O3), an air pollutant and greenhouse gas. The primary source of natural halogens is emissions from marine phytoplankton and algae, as well as abiotic sources from ocean and tropospheric chemistry, but how their fluxes will change under climate warming –and the resulting impacts on O3– are not well known. Here we use an Earth system model to estimate that natural halogens deplete approximately 13 % of tropospheric O3 in the present-day climate. Despite increased levels of natural halogens through the twenty-first century, this fraction remains stable due to compensation from hemispheric, regional, and vertical heterogeneity in tropospheric O3loss. Notably, this halogen-driven O3 buffering is projected to be greatest over polluted and populated regions, mainly due to iodine chemistry, with important implications for air quality.
Quantifying the usefulness of European subseasonal forecasts using a real-world energy-sector framework
Authors: Dorrington Joshua , Finney Isla , Weisheimer Antje , Palmer Tim
Published: March 2020

Increasingly, operational forecasting centres are producing sub-seasonal forecasts, targeted at lead times of 3-6 weeks. These aim to fill the gap between conventional 2-week weather forecasts and longer term seasonal outlooks. However it is often difficult for end-users to know how these sub-seasonal forecasts can be best utilised, and how skilful they are for predicting variables of real world interest.

Much prior work on sub-seasonal forecasts has focused on assessing skill scores for large-scale smooth fields of mid- or upper-tropospheric variables, or else has looked at heavily time-averaged quantities. How to extend the lessons of these studies to user applications is not always obvious.

We take a more applied approach, focused on the chaotic and variable weather of Western Europe. We use sub-seasonal temperature forecasts alongside real-world French energy price and demand data in order to directly calculate the financial value of subseasonal forecasts to users in the energy sector. Using this new, real-world framework we make an estimate of cost-loss ratios and so can compare to the results of a simpler potential economic value model.

 
The structural evolution of pull-apart basins in response to relative plate rotations; A physical analogue modelling case study from the Northern Gulf of California.
Authors: Farangitakis Georgios-Pavlos , McCaffrey Kenneth J.W. , Willingshofer Ernst , Kalnins Lara M. , van Hunen Jeroen , Persaud Patricia , Sokoutis Dimitrios
Published: March 2020

Pull-apart basins are structural features closely linked to the interactions between strike-slip and extensional tectonics. Their morphology and structural evolution are determined by factors such as extension rate, width/length ratio, or changes in the extension direction. In this work, we focus on changes in extension direction during the formation of a pull-apart basin as a basis to further understand the evolution of the northern Gulf of California through a series of physical analogue modelling experiments.

We investigate the effect of a variation in the basin extension direction, using a two-layer ductile-brittle configuration to simulate continental crust rheology. Pull-apart basin development is accomplished by displacing a plastic sheet at the bottom of the experiment, with pre-cut geometry resembling interconnected rift and strike-slip segments, orthogonal to the evolving rift axes. Subsequently, we change the relative motion of the base plate by 7o in accordance with the reconstructed plate vector from the Gulf of California. Oblique extension continues on this new plate motion vector to the end of the experiment.

To analyse the results, we inserted the model cross-sections in a seismic interpretation software generating 3D interpretations for faulting and sedimentary thickness. Preliminary results show that the shift in the direction of plate motion produces sigmoidal oblique slip faults that become normal when deformation adjusts to the new plate motion vector. Furthermore, it appears that sediment distribution is controlled heavily by the relative plate rotation.

Finally, we compare our observations with seismic reflection images, sedimentary package thicknesses and fault interpretations from the pull-apart structure in the Northern Gulf of California transtensional margin, where we find good agreement between model and nature.
Multiple level of CO2 fluxes over Beijing megacity with eddy covariance method
Authors: Liu Yang , Liu Huizhi
Published: March 2020

Based on the CO2 fluxes measured with eddy covariance method from 2008 to 2012 at 47, 140 and 280m in Beijing 325m meteorological tower, we have investigated the exchange process of CO2 flux between atmosphere and the urban surface in Beijing megacity. Because of the total vehicle control from 2011, the increasing rate of annual total CO2 flux at 140m from 2008~2010 is 7.8% while from 2010~2012 is 2.3%. The average annual total CO2 flux during the 5 year measurement is largest at 140m (6.41kg C m-2 yr-1) while at 47 (5.78 kg C m-2 yr-1) and 280m (3.99 kg C m-2 yr-1) are much smaller. The measured fluxes were highly dependent on the prevailing wind direction. The CO2 fluxes at weekends are nearly the same as at weekdays because of the traffic restriction rule during Mon to Fri. Total vehicle numbers and population are main controlling factors of annual total CO2 fluxes in Beijing. The CO2 fluxes at three layers all present positive correlation with road fraction in the footprint area. The R-squares are respectively 0.69, 0.57 and 0.54 at 47, 140 and 280m. The decreasing fraction of vegetation will cause the increasing of annual total CO2 flux and there is a exponential relationship between them. The annual total CO2 flux is larger when the population density is higher.
Serpentinite mud volcanism and exhumation of fore arc- and lower plate material in the Mariana convergent margin system (IODP Expedition 366)
Authors: Kurz Walter , Miladinova Irena , Del Gaudio Arianna V. , Piller Werner , Krenn Kurt
Published: March 2020

Serpentine seamounts located in the forearc region of a subduction zone setting represent an excellent natural laboratory for studying the geochemical processes acting along convergent plate margins and the associated natural hazards as well as the forearc structure and fault patterns. Active serpentinite mud volcanoes are currently restricted only to the Izu-Bonin-Mariana system, where old (presumably Cretaceous) oceanic lithosphere is subducting in the absence of an accretionary prism.

IODP Expedition 366 recovered cores from three serpentinite mud volcanoes at increasing distances from the Mariana trench (Yinazao, Fantangisña and Asùt Tesoru). Most of the material consists of serpentinite mud containing lithic clasts from the underlying forearc crust and mantle as well as from the subducting Pacific plate. A thin cover of pelagic sediments and volcanic ash deposits underlying the mud volcanos were also recovered. Recycled materials from the subducted slab are found at all three mud volcanoes and consist of metavolcanics rocks, metamorphosed pelagic sediments including cherty limestone as well as fault rocks.

Preliminary investigation of recovered sedimentary clasts from the summit of Fantangisña Seamount revealed that they contain primary calcite veins, whereas the latest veins are composed of aragonite (CaCO₃) and barite (BaSO₄).

Recovered clasts from the flank consist mainly of ultramafic rocks with various degrees of serpentinization. The serpentinite veins consist of lizardite and chrysotile, which suggests rather low temperatures of serpentinization (below 200 °C). Petrological analysis of metabasalt clasts from the same drilling hole shows changes in the mineral composition within the different intervals of the core. The composition of clinopyroxene varies between aegirine-augite and omphacite, but augite is also present. The presence of phengite with Si content of 3.5-3.8 a.p.f.u. indicates minimum pressure of 0.7 GPa at ~250 °C.

Furthermore, providing a detailed characterization of the fluids composition and transport would allow the better constraining of the tectonic and metamorphic history as well as the physical properties of the subducting Pacific Plate. Obtaining data on that point is in progress and will be presented additionally.
Significance of meltwater in estimating runoff using Budyko framework in Northwest Xinjiang, China
Authors: Bai Jie , Li Junli , Liu Tie , Bao Anmin
Published: March 2020

Budyko framework has been widely used to estimate the partitioning of precipitation into evapotranspiration and runoff as a function of an aridity index (i.e., ratio of potential evapotranspiration to precipitation) in catchments where snow or glaciers are absent. Where snow or glaciers exist, meltwater from either may considerably affect the performance of the Budyko framework. However such effects have not been investigated in the Xinjiang territory of Northwest China, which features many meltwater-dependent river systems. To analyze the effects of meltwater on hydrological cycles in Xinjiang, we utilized a calibrated hydrological model (Soil and Water Assessment Tool, SWAT) to estimate meltwater from snow or glaciers. The water budgets of 21 catchments across three major mountain ranges of Xinjiang showed that normalized contributions of meltwater to river runoff were respectively 89.9%, 77.0%, and 55.6% in the catchments of Altay, Kunlun and Tienshan Mountains. The results showed that the catchments of Altay Mountains with the highest meltwater ratio (defined as the ratio of meltwater to the sum of meltwater and rainfall, 0.572 ± 0.075) had the lowest Budyko parameter ω (1.238), while those of Tienshan Mountains with the lowest meltwater ratio (0.239 ± 0.143) had the highest ω value (1.348). This indicated that the Budyko parameter ω was negatively correlated to meltwater ratio across three mountains. Incorporating meltwater from snow and glaciers into the Budyko framework significantly increased the values of ω in all three mountain ranges, indicating that the Budyko framework without inclusion of meltwater could under-estimate evapotranspiration in Xinjiang, China. There results derived from this research also implied that both surface runoff and evapotranspiration may increase under a warming climate in mountain areas.
Floods in the Pyrenees region: the PIRAGUA-FLOOD geodatabase
Authors: Aznárez-Balta Marina , Llasat M. Carmen , Llasat-Botija Montserrat , Cortès Maria , Gilabert Joan , Quintana-Seguí Pere
Published: March 2020

The present contribution shows a spatial and temporal analysis of the flood events in the Pyrenees area for the period 1981-2015. Seven regions from Spain, Andorra and France conform the mountain range: Basque Country, Navarra, Aragon and Catalonia, in Spain; Nouvelle-Aquitaine and Occitanie, in France; and Andorra country. Although some flood databases exist for these countries, usually they only include catastrophic flood events for some regions (i.e. FLOODHYMEX – Llasat et al, 2013- include Catalonia and Languedoc-Roussillon). This contribution shows a new flood geodatabase for the whole Pyrenees mountain chain, developed into the framework of the PIRAGUA project (Interreg POCTEFA EFA210/16). In order to have homogeneous information for all the regions, several data sources have been analysed for this period. The methodology used in the database development, the type of information and the structure of the database, are presented. In order to show the localities affected by floods, different maps of the municipal distribution of flood events have been developed. A flood event is defined as an episode along which one or more surface water floods have been recorded in one or more regions. They are usually produced because of heavy rainfall events. Some statistics on temporal distribution, and an identiﬁcation of the most important events have been carried out. 182 flood events have been identified for the whole region, classified in catastrophic, extraordinary and ordinary flood events. 41 flood events affected more than one region and 9 of them were catastrophic in at least one. 11% of the events caused a total of 140 casualties in the study period, showing the importance of orography and land-use on the exposure of mountainous areas to flood events, especially in flash flood events. Besides punctual information on maximum rainfall provided by meteorological stations, the rainfall field has been analysed from the SAFRAN reanalysis. Finally, the weather types associated to the flood events have been obtained using the Jenkinson and Collison classification (Jenkinson and Collison, 1977).

 

Jenkinson AF, Collison FP. 1977. An initial climatology of gales over the North Sea. Technical Report, Synoptic climatology Branch Memorandum No. 62, Meteorological Office, Bracknell, UK, 18 pp.

Llasat MC, Llasat-Botija M, Petrucci O, Pasqua AA, Rosselló J, Vinet F, Boissier L. 2013. Towards a database on societal impact of Mediterranean floods within the framework of the HYMEX project. Nat. Hazards Earth Syst. Sci. 13(5): 1337–1350.
How 'hot' are the hotspots: Statistical approach to localize the high activity areas on soil images
Authors: Bilyera Nataliya , Kuzyakova Irina , S. Razavi Bahar , Spielvogel Sandra , Kuzyakov Yakov
Published: March 2020

The recently raised topic of microbial hotspots in soil needs not only visualizations of their spatial distribution and biochemical analyses, but also statistical approaches to segregate these hotspots and separate them from the background.  We hypothesized that each type of hotspots (e.g. hotspots of root exudation, enzyme activities, root water uptake, pesticides accumulation in plant) is a result of processes driven by biotic or abiotic factors, and consequently corresponds to a statistical distribution follows of a composite functions (e.g. normal/Gaussian), which is significantly different from the background. Consequently, the elucidation of microbial hotspots should be based on statistical separation of the distributions or segregate of maximal values within one distribution. As examples, we collected 3 groups of published images: 1) 14C images on carbon input by roots into the rhizosphere, 14C localization in roots and glyphosate accumulation in the plant, 2) zymogram on leucine aminopeptidase, 3) neutron image on root water uptake. Each of the images was analyzed for statistical distribution of activity and its area. In the next step, respective distribution parameters (means and standard deviations) were calculated, the modeled distribution was fit, and the background was removed. For the parameters with one distribution, we identified hotspots as the areas outside of the “Mean+2SD” values (corresponding to the upper ~ 2.5% of activity being over 95.5 % of background values). Finally, images of solely hotspots locations were visualised. Comparison with previously used decisions of the hotspot intensity (i.e. Top-25% intensity) thresholding showed advantages of the “Mean+2SD” approach. The advantages (suitable for “time-specific” hotspots in temporal sequence of images, identification of hotspots with different level of activity, unification of thresholding approach for several imaging methods with different principles of activities distribution) and limitations (loss of hotspot areas at low quality images, several thresholding rounds for two or more distributions at on image) of the suggested approach and the potentials of its further development were discussed. We conclude that objective elucidation and separation of the hotspots is case specific and should be based on statistical tools of distribution analysis, which will also help to understand the processes responsible for the highest activities.
The quasi-global geographical distribution of precipitation system scale
Authors: Zhang Yan , Wang Kaicun
Published: March 2020

The scale of precipitation systems can provide important information to acquire a better understanding of formation mechanism and environmental effects of precipitation as well as model promotion. However, the global geographical distribution of precipitation system scale remains poorly known from previous studies. This study uses the latest Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) data to get global patterns of precipitation system scale by grouping the contiguous rainy gridboxes during 2015-2018. Our results show that the large precipitation systems (>103 km) occur more frequently over ocean and the midlatitude land areas with low precipitation amount such as Siberia as well as the western and central parts of North America. The most apparent seasonal variation of precipitation system scale occurs over midlatitude ocean along with the northern and southern coast of South America. Most regions of the world have the highest peak in the late afternoon at around 17:00 local time (LT). In a statistical average, the relationships between scale and other precipitation properties including amount, frequency, intensity and duration all seem to be positive. The strongest associations of scale with amount, frequency, intensity and duration all occur over tropics and ocean with the highest correlation coefficient greater than 0.8.
Aesthetic evaluation of wind turbines in stochastic setting: Case study of Tinos island, Greece
Authors: Manta Eleni , Ioannidis Romanos , Sargentis Georgios-Fivos , Efstratiadis Andreas
Published: March 2020

Wind turbines are large-scale engineering infrastructures that may cause significant social reactions, due to the anticipated aesthetic nuisance. On the other hand, aesthetics is a highly subjective issue, thus any attempt towards its quantification requires accounting for the uncertainty induced from subjectivity. In this work, taking as example the Aegean island of Tinos, Cyclades, Greece, we present a stochastic-based methodology for evaluating the feasibility of developing wind parks in terms of their aesthetic impacts. At first, a field analysis is been conducted along with photographic surveying, 3D representation and the opinion of the target population regarding the development of wind parks across the island. Subsequently, the landscape transformations that will be caused from the wind turbines are assessed according to the theory of aesthetics, which are depicted by using suitable spatial analysis tools in GIS environment. The 3D representation images along with the maps are finally assessed through stochastic analysis, in order to quantify the visual impacts to the landscape and the nuisance to local community.
Combining geostatistics and physically-based simulations to characterize contaminated soils
Authors: Le Coz Mathieu , Pannecoucke Léa , Freulon Xavier , Cazala Charlotte , de Fouquet Chantal
Published: March 2020

Characterization of contamination in soils resulting from nuclear or industrial activities is a crucial issue for site remediation. A classical approach consists in delineating the contaminated zones based on a geostatistical estimation calibrated from measured activities, but it results in high uncertainties when the number of measurements is low and/or the spatial variability of the studied variable is governed by complex processes. In order to reduce these uncertainties, a novel approach, called Kriging with Numerical Variogram (KNV), is developed: the variogram is computed from a set of physically-based flow-and-transport simulations rather than from the measurements.

The KNV approach is assessed on a two-dimensional synthetic reference test case reproducing the migration of a tritium plume within an unsaturated soil with hydraulic properties highly variable in space. The results show that the mean absolute error in estimated activities is 50% to 75% lower with KNV compared to classical geostatistical approaches, depending on the sampling scenario. Moreover, KNV leads to a significant reduction of the empirical error standard deviation, which reflects uncertainties on the estimated activities. The performance of KNV regarding the classification into contaminated or not-contaminated zones is yet sensitive to the contamination threshold.

The KNV approach could thus help to better estimate volumes of soils to be decontaminated in the context of remediation of nuclear or industrial sites. This approach can be transposed to other scales of heterogeneities, such as systems with several geological units, or other pollutants with a more complex chemical behavior, as soon as a numerical code that simulates the phenomenon under study is available.

This study is part of Kri-Terres project, supported by the French National Radioactive Waste Management Agency (Andra) under the “Investments for the Future” national program.
Post-wildfire flash flooding in small mountainous catchments: post-fire effects and characteristics of the November 2019 flash flood in Kineta, Greece
Authors: Filis Christos , Spyrou Nafsika Ioanna , Diakakis Michalis , Kotroni Vassiliki , Lagouvardos Konstantinos , Papagiannaki Katerina , Vassilakis Emmanuel , Milios Dimitrios , Lekkas Efthymios
Published: March 2020

During the period 24-25 November 2019 a low pressure system with organised convective storms has affected Greece as it crossed the country from west to east. The system, which was name Gyrionis, after a name used in the Greek mythology, has produced heavy rainfall, with increased lightning activity and local hailstorms. In the area of western Attica the maximum rainfall has been reported with 92 mm of on 24 November and additional 115 mm in 25 November, adding to a storm total of 206 mm, which caused flash floods in the town of Kineta. The storm caused overflowing of local torrents draining the south slopes of Geraneia Ori, inducing significant damages in property and infrastructure mainly within the town and across the coastal zone.

Field surveys showed that a wildfire that burned through almost the entire catchment of the main torrent (named Pikas) on 2018, played a crucial role in flooding and its impact on the town. At critical locations along the river, vegetation debris and eroded material of various grain sizes, including boulders, diminished dramatically the hydraulic capacity of the river, intensifying flooding in the downstream areas, which formed an alluvial fan.

Based on comparison of pre- and post-flood aerial photography of the burned area, a major source of this deposited material was identified as burned trees still standing after the fire, uprooted from the river banks of the main channel and carried away together with additional soil debris. The material was jammed at a crucial location near the apex of the alluvial fan causing floodwaters to overflow and inundate significant parts of the fan’s apron, a geomorphological setting that increased the extent and impact of flooding further.

Overall, the case of Kineta, is a characteristic case of post-wildfire flash flooding, in which the fire effects are critical in the enhancement of subsequent flooding phenomena.
The Effect of Artificial Macropores on the Amount of Organic Matter in Soils and Plant Biomass.
Authors: Mori Yasushi
Published: March 2020

Artificial macropores constructed of fibrous material were installed in degraded red-yellowsoils to enhance vertical infiltration of organic matter and nutrients. This can enhance vertical infiltration without cultivation which causes small particle loss from the surface soils.  Macropore and control (no macropore) plots were established and total carbon was measured at 10, 30, 50 cm depths every six months. Infiltrated soil water was sampled using a capillary force soil water sampler to measure total organic carbon and ion concentration. Results showed that soil total carbon increased in the macropore plot in spring and decreased in fall. The control plot showed few fluctuations. Total carbon concentrations in the soil water also increased in the macropore plot, which may be caused by introducing surface water into artificial macropores. In addition, nitrate nitrogen was higher in the summer in the macropore plot, representing a biological decomposition of organic matter and nutrients for plant growth. The plant biomass in the macropore plot was two times larger than that in control plot and the number of plant species also increased relative to the control plot. This vegetation represents a possible organic matter source for future soils. Finally, the carbon increment in low nutrient soils after macropore installation was calculated as 0.0036 g-C·g-soil−1·yr−1 (20.4 t-C·ha−1·yr−1), which was very successful. This study demonstrates that the relatively simple technique of installing artificial fibrous macropores can increase organic matter and recover vegetation in poorly drained soils.
Tsunami hazard associated to earthquakes along the French coasts. A probabilistic approach (PTHA).
Authors: Souty Viviane , Gailler Audrey
Published: March 2020

Probabilistic Tsunami Hazard Assessment (PTHA) is a fundamental tool for producing time-independent forecasts of tsunami hazards at the coast using data from tsunami generated by local, regional and distant earthquake source. If high resolution bathymetry and topography data at the shoreline are available, local tsunami inundation models can be developed to identify the highest risk areas and derive evidence-based evacuation plans to improve community safety.
This study takes part of the H2020-Euratom NARSIS project (2017-2021), which aims at making significant scientific updates of some elements required for the Probabilistic Safety Assessment, focusing on external natural events (earthquake, tsunami, flooding, high speed winds...). In this framework, we are developing a PTHA approach to estimate the tsunami hazard along the French Mediterranean coasts at a local level. The probability of occurrence of tsunamigenic earthquakes is the foundation of our work as wrong probabilities would lead to a wrong evaluation of the tsunami hazard. We first discuss the various uncertainties from the determination of the tsunami sources to the simulation of the propagation of the tsunami to the coast. We then present the results of tsunami hazard in the city of Cannes (French Riviera).
Investigating the relationship between soil moisture and evapotranspiration at different surfaces. Do we improve fluxes just improving the land use in models?
Authors: Román-Cascón Carlos , Lothon Marie , Lohou Fabienne , Brut Aurore , Hartogensis Oscar , Merlin Olivier , Ojha Nitu , Yagüe Carlos , Soriguer Ramón , Díaz-Delgado Ricardo , Andreu Ana , González-Dugo Maria P.
Published: March 2020

A correct spatial representation of the surface energy balance is still a challenge. In a first step, and assuming a correct knowledge of the incoming short-wave radiation, it is the land cover that mostly controls the albedo and the long-wave radiation emitted to the atmosphere, influencing significantly the net radiation available at the surface and the surface temperature. In a second step, the partitioning of this energy into evapotranspiration and sensible heat flux is, in part, controlled by the availability of soil moisture but also by the type, characteristics and physiological state of the vegetation covering the surface, since plants provide a pathway for soil moisture to the atmosphere through transpiration.

Hence, to correctly model the surface energy balance, we face three main challenges: an appropriate representation of the land use, soil moisture and a correct modelling of how plants regulate their stomatal behaviour under different soil-moisture limited conditions.

In this work, by using in situ data we explore the relations between soil moisture and evapotranspiration from several vegetation types at different soil-moisture limited regions: a wetter area in the south of France and a drier one in the south of Spain. For this, we try to distinguish different periods and vegetation states. Since significant differences are observed for the various plant types, we investigate whether using a more realistic and higher-resolution land-use database in the Weather Research and Forecasting (WRF) model improves the simulation of soil moisture and surface fluxes.
The outstanding 2019 Heatwaves in Central Europe – driving mechanisms and soil-atmosphere feedbacks
Authors: Trigo Ricardo , Sousa Pedro , Barriopedro David , García-Herrera Ricardo , Ordóñez Carlos , Soares Pedro
Published: March 2020

In the current study, we analyzed the two outstanding heatwaves (HWs) that affected Europe in summer 2019. The events occurred in late June and late July and were record-breaking, although peak temperatures were observed in distinct areas. During the June HW the highest temperatures were recorded in SE France, when the country registered for the first time temperatures above 45ºC. The July HW made thermometers cross the psychological barrier of 40ºC for the first time in Belgium and the Netherlands, breaking all-time records in widespread areas of Central Europe.

We detected that a subtropical ridge fostering warm advection from lower latitudes was a common feature for both HWs. However, we have also found distinct mechanisms shaping the two HWs. While the June HW was predominantly characterized by the intrusion of a vertically homogenous air mass of Saharan origin, surface processes and upward transport of sensible heat were pivotal for the July HW. Our results suggest that the intensity and extension of the June HW contributed to soil desiccation, which together with the persistence of dry and clear sky conditions during early July led to an amplification of the surface temperature anomalies during the late July HW. This is supported by a flow analogue exercise, showing amplified surface heating for flow analogues of the July HW when they are preceded by short-term dry soil moisture conditions, like those caused by the June HW. In turn, we show that, in agreement with the long-term regional warming, soil desiccation during the June 2019 event was larger than it would have been in the recent past (assessing 1984-2018 versus 1950-1983). Finally, we compared the spatio-temporal distribution of summer temperature for 2019 and the previous record-breaking summer 2003. Results show that an outstanding warming fingerprint (circa +1.5ºC in summer daily maximum temperatures averaged over Europe) has been superimposed on the relatively larger magnitude of the August 2003 HW (with respect to the climatology at that time), thus explaining the exceptionality of the record-breaking values observed in 2019.

This work was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project IMPECAF (PTDC/CTA-CLI/28902/2017).