bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating STARE with relational databases
Authors: Griessbaum Niklas , Rilee Mike , Frew James , Kuo Kwo-Sen
Published: March 2021

When working with ungridded remote sensing data, such as swath surface reflectance like Moderate Resolution Imaging Spectroradiometer (MODIS) MOD09 or Visible Infrared Imaging Radiometer Suite (VIIRS) VNP09, extracting targeted information of interest from a collection of granules can be a challenging exercise. Given a region of interest (ROI), it is tedious both to determine the subset of granules that intersect the ROI, as well as identifying, within the granules, the individual instantaneous field of views (IFOVs) contained by the ROI.

The SpatioTemporal Adaptive-Resolution Encoding (STARE) is an indexing scheme that recursively divides the Earth's surface into quadtree hierarchies, allowing triangular elements ("trixels") of varying sizes (resolutions) to be identified with unique index values. STARE is also a software library that operates on STARE indices. It can efficiently determine the spatial relationship between two trixels, by evaluating their index values, if the trixels share a common path in the STARE tree structure. By representing geographical regions as the sets of trixels with adaptive resolutions that tesselating them, STARE provides an elegant method to determine geospatial coincidence of arbitrarily shaped geographic regions, with accuracy up to ~7-8 cm in length. 

In this presentation, we introduce STARELite, a SQLite STARE extension and its use for cataloguing volumes of remote sensing granules that researchers often possess in their local storage. In this application, STARELite is used to determine subsets of granules intersecting arbitrary ROIs. Further, STARELite can be used for the inverse search problem: Determining all spatially coincident granules of an individual granule. STARELite leverages other components of the STARE ecosystem; namely STARE sidecars, which hold the trixel index values of each iFOV and a set of trixels representing the cover of each granule; STAREMaster, which is used to generate STARE sidecar files; and STARPandas, a Python Pandas extension used to bootstrap STARELite databases.

Given the limitations of SQLite, STARELite is to be understood as a proof of concept for the integration of STARE into relational databases in general. 
Henri Poincare’s legacy for tipping points
Authors: Blaustein Richard
Published: March 2021

The science of Earth system and climate tipping points has evolved and matured as a disciplined approach to understanding anthropogenic and non-anthropogenic stresses on the Earth’s subsystems in the 21st century. However, tipping points is strongly interlinked with the science of bifurcations and dynamical systems, which received a seminal and resonant illumination by the great French mathematician Henri Poincare (1854-1912). Thus, quite a few historically minded tipping point scientists mention Poincare as the seminal, path-setting thinker for tipping point understandings.

Moreover, Poincare’s bifurcation and dynamical systems-pertinent science is also linked to his seminal role in chaos theory, which illuminates today’s understanding of climate stochasticity. Poincare famously said, "A very small cause which escapes us determines a considerable effect that we cannot see; so, we say this effect is random," which provided grounding for the chaos notion of critical sensitivity to initial conditions. Since Poincare, great strides in abrupt change understanding as linked to chaos (and within an examination of turbulence) have taken place in the science that informs tipping points, such as with the work of Ed Lorenz and David Ruelle. Additionally, the Russian mathematicians (e.g., Andronov and Arnold) have contributed greatly with the refining of differential equations for bifurcation understandings that Poincare began.  

This EGU presentation is a history of science presentation on Henri Poincare's commencement of bifurcation, dynamical system and chaos understandings as presented by a journalist who has done both interviews and general historical research. The presentation sets key points in Poincare’s biography and pertinent career and sketches the legacy of this Poincare focus up from Henri Poincare through Russian bifurcation scientists, catastrophe theorist Rene Thom, and ultimately Lorenz and current bifurcation theorists, such as Michael Ghil and Valerio Lucarini. It offers light on the ancestry of one of the most important examinations of the Anthropocene, climate change tipping points.  
Investigation of long-term changes of coastal wave directionality patterns and their connections with NAO climatic index: UK case study
Authors: Chatzirodou Antonia
Published: March 2021

The effects of climate change are at the spotlight of scientific research. In coastal science the effects of sea-level rise (SLR) on coastal areas, mainly as a result of melting of ice sheets and thermal volume expansion consist an intensive area of research. As well the changing ocean wave field due to greenhouse effect and interactions of atmospheric processes is under investigation. Researchers have placed focus on significant wave height changes and their associated impacts on the coastal environment, with evidence suggesting that the number, intensity and location of storms will change. It is suggested that equal attention should be placed on the mean wave direction changes and the effects that these changes may have on the coastlines and surrounding coastal infrastructure. Following that, this study investigated the changes in wave direction data since 1979 to 2019 covering 40 years’ time period at 11 offshore UK coastal locations. The selected locations lie close to WaveNet, Cefas’ strategic wave monitoring network points for the UK. Stakeholders use the data to provide advice and guidance to all involved parties including responders and communities about coastal flood risk. On a longer timescale the data provide evidence to coastal engineers and scientists of the wave climate change patterns and the implications this may have on coastal structures and flood defences design. Based on this initiative, this study investigated UK offshore wave climate changes by performing a longer timescale analysis of changes of wave direction patterns. The wave direction data were taken from ECMWF ERA5 6-hour hind cast data catalogue which covers 40 years’ time period from 1797-2019 (Copernicus Climate Change Service (C3S), 2017). MATLAB software coding was primarily utilized for data processing and analyses. Following that, inferential statistics were applied to map inter-decadal statistical changes in wave direction patterns, suggesting that wave directionality patterns have presented changes at 11 offshore locations tested.  The connections of wave directions with North Atlantic Oscillation (NAO) Climatic Index are currently investigated through use of machine learning approaches. The results of this study can be confidently used in wave transformation computational models coupled with hydro-morphodynamic models to downscale offshore wave direction changes to UK coastal areas. This can help identify susceptible coasts to offshore wave climate change. Susceptibility is regarded in form of coastal erosion and accretion rates changes as a result of altered offshore wave conditions, which might affect coastal flood risk with potential impacts on critical infrastructure.  
Emergence of multisectoral impacts of the global warming during the 21st century.
Authors: Brouillet Audrey , Sultan Benjamin
Published: March 2021

The current observed global warming is projected to intensify by the end of the 21st century. According to simulations of the climate system and its impacts on populations, previous studies show significant projected impacts on four main sectors: water, health, energy and agriculture. Concurrent analyses have also focused on the time of emergence (ToE) of future climate modifications to assess when new climate regimes will emerge from a prior reference. Here we propose to investigate the timing and the emergence of global warming impacts on populations over three main vulnerable regions: Western Africa (WAF), Eastern Africa (EAF) and South-eastern Asia (SEA). We propose to analyse multi-sectoral impacts that may affect human being by accounting for (but not limited to) 6 fields: crop failure, water scarcity, health, droughts, floods, and heatwaves. The ISIMIP2b protocol (phase 2b of the Intersectoral Impact Model Intercomparison Project), which provides simulated impacts from 1 to 8 sectoral impact models and four CMIP5 (5th phase of the Coupled Model Intercomparison Project) climate models, is used in this study.

              Preliminary results under the RCP8.5 future climate scenario show a strong acceleration of the decrease of the annual maize yields before 2048 in WAF and EAF according to the CLM45 impact model, suggesting a significant emergence at this time. No particular fluctuation from the long-term trend is shown in SEA. CMIP5 climate forcing (i.e. GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR and MIROC5) responses in maize yields exhibit larger uncertainties over EAF than over WAF and SEA. Drought metrics such as the annual number of consecutive dry days (i.e. daily precipitations < 1mm) and the annual number of periods with more than 5 consecutive dry days show an acceleration of their increases around 2052 in WAF with large climate forcing uncertainties, but no significant emergence over EAF and SEA. Flood metrics from the ORCHIDEE impact model simulations do not exhibit particular fluctuation nor acceleration of the change during the 21st century in the three regions. The next step of our study is to quantify the ToE of the significant fluctuations compared to the long-term trends of the different metrics that cover every impact sectors. The Kolmogorov-Smirnov test (‘KS-test’) method will be applied as the statistical approach to quantify the ToE independently from the signal shape. Impact models uncertainties will also be quantified compared to the climate model uncertainties, in order to assess whether impact or climate modelings is the main driver of the total uncertainties when studying the emergence of the impacts of global warming.
Radiative forcing of atmospheric brown clouds over the Indo-Gangetic Plain
Authors: Jangid Manish , Mishra Amit
Published: March 2021

Atmospheric brown clouds (ABCs) are a dense and extensive pollution layer and have significant implications on air quality, agriculture, water cycle, and regional climate. The objective of the present study is to observe seasonal and spatial variations in the occurrence of ABCs and its radiative effects. The Indo-Gangetic plain (IGP) is the most populated region of India, which is an extended region in the foothills of the Himalayas. The IGP is one of the ABCs hotspots over the globe. The frequency of ABCs occurrences and radiative forcing were calculated using data from seven ground-based remote sensors situated across the IGP. We have used total ~ 5000 days of Level-2 aerosol measurements from seven AERosol Robotic NETwork (AERONET) stations (Karachi, Lahore, Jaipur, New Delhi, Kanpur, Gandhi college and Dhaka University) for three seasons (Pre-monsoon, Post-monsoon, and Winter) during 2000-2019. An algorithm based on the optical properties of aerosols is used to defined extreme pollution events (ABCs days) for each site. Our results show more frequent occurrences of ABCs over the region in the pre-monsoon out of all three seasons. However, spatial variation is found in all seasons, like maximum frequency of ABCs over western IGP region in post-monsoon and minimum is at eastern IGP region in the winter season. Further, we have used the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model to calculate radiative forcing during ABCs days on all sites of study. Aerosol optical depth (AOD) and absorption optical depth (AAOD) was used to calculate radiative forcing over the IGP region. Radiative forcing of ABCs is negative at both the surface (SRF) and top of the atmosphere (TOA), whereas it is positive in the atmosphere (ATM). In magnitude, it was found minimum in the pre-monsoon season at TOA. However, other seasons have specific features over specific locations, for example, in the winter season, radiative forcing is maximum over Kolkata at TOA, SRF, and ATM, which are -13.81 W/m2, -50.90 W/m2, and +37.09 W/m2 respectively. In the pre-monsoon season, radiative forcing is maximum at Delhi (-9.59 W/m2) at TOA. In post-monsoon season radiative forcing maximum at Gandhi-college (-11.30 W/m2) at TOA. This ground observation is also compared with Modern Era Retrospective analysis and Research and Applications-2 (MEERA 2) modal data. These results indicate the cooling effect of ABCs at the surface and TOA over the IGP region throughout the period.
Soil moisture assessment based on Sentinel 1/2 and in-situ data: The vineyard case study
Authors: Mendes Maria Paula , Falcão Ana Paula , Matias Magda , Gomes Rui
Published: March 2021

Vineyards are crops whose production has a major economic impact in the Portuguese economy (~750 million euros) being exported worldwide. As the climate models project a larger variability in precipitation regime, the water requirements of vineyards can change and drip irrigation can be responsible for salt accumulation in the root zone, especially when late autumn and winter precipitation is not enough to leach salts from the soil upper horizons, turning the soil unsuitable for grape production.

The aim of this work is to present a methodology to map surface soil moisture content (SMC) in a vineyard, (40 hectares) based on the application of two classification algorithms to satellite imagery (Sentinel 1 and Sentinel 2). Two vineyard plots were considered and three field campaigns (December 2017, January 2018 and May 2018) were conducted to measure soil moisture contents (SMC). A geostatistical method was used to estimate the SM class probabilities according to a threshold value, enlarging the training set (i.e., SMC data of the two plots) for the classification algorithms. Sentinel-1 and Sentinel-2 images and terrain attributes fed the classification algorithms. Both methods, Random Forest and Logistic Regression, classified the highest SMC areas, with probabilities above 14%, located close to a stream at the lower altitudes.

RF performed very well in classifying the topsoil zones with lower SMC during the autumn-winter period (F-measure=0.82).

This delineation allows the prevention of the occurrence of areas affected by salinization, indicating which areas will need irrigation management strategies to control the salinity, especially under climate change, and the expected increase in droughts.
A hybrid system for the near real-time modeling and visualization of extreme magnitude earthquakes
Authors: Cabrera Flores Eduardo César , Chavez Mario , Salazar Alejandro
Published: March 2021

Among other natural hazards, the occurrence and impact of extreme magnitude earthquakes are of great interest both from the scientific and societal points of view. The scarcity of observational instrumental data for these type of events, as well as the urgent need to take mitigation measures to minimize their effects on human life and critical infrastructure have required the development of computational codes for the modeling of the propagation of these events. 

Examples of the realistic modeling of the propagation of extreme magnitude earthquakes that can be achieved by the use of powerful HPC facilities and 3D finite difference Fortran codes have been presented by Cabrera et al. 2007 and Chavez et al. 2016. These large-scale scientific simulations generate vast amount of data, writing such data out to storage step-by-step is very slow and requires expensive I/O post-processing procedures for their analyses. However, the current and foreseen major advances occurring in Exascale HPC systems offer a transformational approach to the research community, as well as the possibility for the latter of contributing to the solution of urgent and complex problems that society is or will be facing in the years to come.

Taking into account the future exascale developments and in order to speed-up in situ analysis, i.e., analyze data at the same time simulations are running, in this ongoing research we present the main computational characteristics of the hybrid system we are developing for the near real-time simulation and visualization of the propagation of the realistic modeling of the 3D wave propagation of extreme magnitude earthquakes. The system is based on the updated version the staggered finite difference Fortran code 3DWPFD, coupled with an efficient visualization C++ code. The system is being developed in the hybrid HPC Miztli of UNAM, Mexico, made up of CPUs (8344 cores) + GPUs (16 NVIDIA m2090 and 8 V100). We expect to fully adapt the code for emerging hybrid Exascale architectures in the near future. Examples of the results obtained by using the hybrid system for the modeling of the propagation of the extreme magnitude Mw 8.2 earthquake occurred the 7 September 2017 in southern Mexico will be presented.
Evaluation of Safety and Effectiveness of  Localized Arctic Ice Albedo Restoration Method to Slow Climate Change Impacts
Authors: Field Leslie
Published: March 2021

The continuing acceleration of climate change and its impacts point to a need to consider climate interventional solutions. Climate restoration solutions can join climate mitigation and adaptation measures to bring a needed third option to climate stability.  Such solutions require thorough vetting through research and development, including climate modeling, materials evaluation, safety testing, and small-scale field testing conducted with permissions, transparency, and collaboration with the community, to allow careful evaluation of effectiveness, safety, and cost. International policy and governance are required to determine, given the information developed in the R&D, what solutions are in the best interests of humanity, so they can be funded and implemented at a scale to stabilize climate, in time to prevent or reduce climate-change-related harms. 

Ice loss in the Arctic, initially an outcome of global temperature rise, is now a driver accelerating global temperature rise, as the Earth’s Arctic ice cover has diminished rapidly. NOAA reported in 2018 that 95% of the most-reflective multi-year ice has disappeared over the past 40 years. The effect of this lost Arctic reflectivity is to increase the net energy influx to the Arctic, accelerating heating locally and worldwide, leading to increasing climate- related impacts on populations and ecosystems.
Arctic Ice Project’s focus is on evaluating and developing an innovative solution to artificially restore lost Arctic reflectivity using thin layers of hollow glass microspheres to reverse the increased summer radiative forcing from the Ice-Albedo Feedback Effect. We will report on the physical characterization of the HGMs proposed for this use, the approach taken for field testing and safety evaluations, and the strategy for evaluating and modeling where to conduct limited deployment of this restoration method to achieve the most leveraged positive impact.
Restoring Arctic ice reflectivity has the potential to be the largest single safe lever that could be practically and effectively deployed in the short term to give the world the time needed to complete the needed transition to sustainable practices, while reducing climate devastation. 

The Arctic Ice Project is focused on developing this needed information, through extensive international collaborations, to evaluate the safety and effectiveness of a proposed localized intervention to restore ice reflectivity in the Arctic. 
Effects of land use, short-term drought and warming on microbial responses to drying and rewetting
Authors: Leizeaga Ainara , Hicks Lettice , Brangarí Albert , Cruz-Paredes Carla , Wondie Menale , Sanden Hans , Rousk Johannes
Published: March 2021

Climate change predicts an increase in temperature and an intensification of the hydrological cycles resulting in more extreme drought and rainfall events. When dry soils experience a rainfall event, there is a big CO2 release from soil to the atmosphere which is regulated by soil microorganisms. In the present study, we set out to investigate how drought and warming affects the soil microbial responses to drying and rewetting (DRW); and how those responses are affected by differences in land use. Previous work has shown that exposure DRW cycles in the laboratory and in the field can induce faster recovery (more ‘resilient’) of the microbial responses after a DRW cycle. In addition, a history of drought has been suggested to result in microbial communities with higher carbon use efficiency (CUE) during DRW in a wet heathland in Northern Europe and in semi-arid grasslands in Texas. We wanted to extend these observations to subtropical environments.

 

With the aim of simulating drought and warming, rain shelters and open top chambers (OTC) were installed in Northern Ethiopia in 2 contrasting land-uses (a degraded cropland and a pristine forest) for 1.5 years. Soils were then sampled and exposed to a DRW cycle in the laboratory. Microbial growth and respiration responses were followed with high temporal resolution over 3 weeks, as well as, changes in microbial community structure.  

 

Microbial functions universally showed a resilient response after a DRW cycle, with bacterial growth and fungal growth increasing immediately upon rewetting linked with the expected respiration response. The field treatments and land-use differences, therefore, did not have an effect on the resilience of soil microbial communities to DRW cycles. There were differences between the two main decomposer groups: fungi were more resilient than bacteria, as they showed a faster recovery rate. Microbial CUE upon rewetting responded differently in the different field treatments and land-uses. CUE was generally higher in croplands than in forests. Besides, while simulated drought reduced CUE, simulated drought increased CUE. These differences might be explained by either (i) the selection or more efficient microbial communities due to a higher exposure to DRW events or (ii) differences in resource availability (i.e. plant input).  
Anomalous Dielectric Variability in the central peak of Tycho crater on the Moon: New insights from Mini-RF S-band Observations
Authors: Shukla Shashwat , Patterson Gerald Wesley
Published: March 2021

One of the unique candidates to explore the evolution of physical surface processes on the Moon is Tycho, a dark haloed impact crater representing well-preserved bright ray pattern and intact crater morphology. Sampling of the central peak in such complex crater formation proves significant in terms of unraveling intriguing science of the lunar interior. With the current state-of-the-art radar technology, it is possible to evaluate the response of the geologic features constrained in the near surface and subsurface regolith environments. This can be achieved by modelling the dielectric constant of media, which is a physical parameter crucial for furthering our knowledge about the distribution of materials within different stratigraphic layers at multiple depths. Here, we used the applicability of Mini-RF S-band data augmented with a deep learning based inversion model to retrieve the dielectric variations over the central peak of the Tycho crater. A striking observation is made in certain regions of the central peak, wherein we observe anomalously high dielectric constant, not at all differentiated in the hyperspectral image and first Stokes parameter image, which usually is a representation of retrieved backscatter of the target. The results are also supported by comparing the variations in the scattering mechanisms. We found those particular regions to be associated with high degree of depolarization, thereby attributing to the presence of cm- to m- scale scatterers buried within a low dielectric layer that are not big enough to produce even-bounce geometry for the radar wave. Moreover, we also observe high rock concentration in the central peak slopes from DIVINER data and NAC images, indicating the exposure of clasts ranging in size from 10 meter to 100s of meter. Furthermore, from surface temperature data, these distinctive outcrops sense warmer temperature at night than the surrounding, which suggests the existence of thermal skin depth in such vicinities. Interestingly, we are able to quantify the pessimistic dielectric constant limit of the large boulder in the middle of the central peak, observable at the Mini-RF radar wavelength, as 4.54 + j0.077. Compared to the expected dielectric constant of rocks, this value is lowered significantly. One probable reason could be the emergence of small radar shadows due to the rugged surface of the boulder on the radar illuminated portion. From our analysis, we showcase the anomalous dielectric variability of Tycho central peak, thereby providing new insights into the evolution of the impact cratering process that could be important for both science and necessary for framing human or robotic exploration strategies.  
Characterization of mesocyclonic rotation in severe convection over the Swiss Alps
Authors: Feldmann Monika , Gabella Marco , Berne Alexis
Published: March 2021

Persistent rotation is a strong indicator of severe weather hazards in convective storms. This work presents a multi-year record of mesocyclonic rotation tracks derived from archived operational radar data in Switzerland. In addition to the general occurrence, underlying seasonal and daily trends, as well as the influence of synoptic weather situation and terrain are explored.
The applied mesocyclone detection presents a combination of thunderstorm cell detection and tracking and rotation identification. The thunderstorm cell detection hereby isolates areas of interest, that are then feed into the rotation detection. The complex terrain of the Swiss Alps and the different environmental conditions leading to persistent rotation in convection required some adaptations to the typical definition of mesocyclonic rotation. A combination of rotational velocity, vorticity, vertical extent and temporal continuity are used to detect mesocyclonic rotation and identify their tracks.
The multi-year record shows considerable variability between the years. A large number of rotation tracks however does not necessarily correspond to a large number in thunderstorms. There is no strict preference on rotation direction, with a slightly higher fraction of cyclonic detections over anticyclonic detections. A spatial overview of the identified events clearly shows the influence of terrain. Pre-Alpine valleys, particularly with lakes, seem to provide favorable conditions for rotation in convection. The largest incidence is located to the South of the Alps in the valleys of the lakes Maggiore, Lugano and Como.
Is Coulomb Stress the Best Choice for Aftershock Forecasting?
Authors: Sharma Shubham , Hainzl Sebastian , Zöller Gert , Holschneider Matthias
Published: March 2021

The Coulomb failure stress (CFS) criterion is the most commonly used method for predicting spatial distributions of aftershocks following large earthquakes. However, large uncertainties are always associated with the calculation of Coulomb stress change. The uncertainties mainly arise due to nonunique slip inversions and unknown receiver faults; especially for the latter, results are highly dependent on the choice of the assumed receiver mechanism. Based on binary tests (aftershocks yes/no), recent studies suggest that alternative stress quantities, a distance‐slip probabilistic model as well as deep neural network (DNN) approaches, all are superior to CFS with predefined receiver mechanism. To challenge this conclusion, which might have large implications, we use 289 slip inversions from SRCMOD database to calculate more realistic CFS values for a layered half‐space and variable receiver mechanisms. We also analyze the effect of the magnitude cutoff, grid size variation, and aftershock duration to verify the use of receiver operating characteristic (ROC) analysis for the ranking of stress metrics. The observations suggest that introducing a layered half‐space does not improve the stress maps and ROC curves. However, results significantly improve for larger aftershocks and shorter time periods but without changing the ranking. We also go beyond binary testing and apply alternative statistics to test the ability to estimate aftershock numbers, which confirm that simple stress metrics perform better than the classic Coulomb failure stress calculations and are also better than the distance‐slip probabilistic model.
Risk management and response process of moraine lakes GLOF in southwestern Tibet (China)
Authors: Wang Xiang , Chen Guo , Dai Xiaoai , Zhao Jingjing , Liu Xian , Gao Yu , Zhang Junmin , Chen Yongjun , Li Xiaozhen , Qin Wenyi , Wang Peng
Published: March 2021

The southwestern part of Tibet in China is one of the hardest-hit areas where Glacier Lake Outburst Flood (GLOF) occurs frequently in the Moraine Lakes of Himalayas. In the face of the increasingly severe GLOF threat of Moraine Lakes, it is urgent to build a risk management and response process of moraine lakes GLOF in this region.  Therefore, we propose a multi-module, process-oriented approach to GLOF risk response (Monitoring-Evaluation-Simulation), which integrates remote sensing, field surveys, Geographic Information Science (GIS), mathematical evaluation models, and hydrodynamic models to carry out the monitoring and analysis of GLOF, susceptibility evaluation, and numerical simulation work in Moraine Lakes.  In the monitoring section (remote sensing and field surveys), we find that typical Moraine Lakes in southwestern Tibet continue to expand in area and are prone to GLOF, which is mainly due to significant area expansion, large-scale ice/avalanches and landslides, and overflow or seepage at the terminal moraine dam. In the assessment part, based on the susceptibility evaluation factor of the glacial lake obtained by monitoring. We creatively use the grey correlation model to filter the GLOF susceptibility evaluation factors, so that the constructed GLOF susceptibility evaluation model has achieved good results (the model evaluation accuracy rate reached 84%, and the AUC value reached 0.874). In the modeling part, the GLOF modeling was carried out for the glacial lakes with high GLOF susceptibility determined by the assessment. It is also the first time that the FLO-2D model is used to construct the GLOF process of a typical Moraine Lake in the Himalayas. The simulation results show the effective simulation capability of the FLO-2D model (the simulated flow depth and flow velocity errors are both within 10%). In short, realizing the organic combination of monitoring, evaluation and simulation are one of the main advantages of the "Monitoring-Evaluation-Simulation" method. This approach effectively supports the prevention and control of GLOF in Moraine Lakes in southwestern Tibet and provides a new application idea for the risk management and response of GLOF in regional Moraine Lakes.

 
Stratospheric aerosol enhancement and decay after Raikoke eruption in July 2019 as observed from Tbilisi, Georgia and Halle, Belgium using ground-based twilight sky brightness spectral measurements.
Authors: Mateshvili Nina , Fussen Didier , Mateshvili Iuri , Vanhellemont Filip , Bingen Christine , Paatashvili Tamar , Kyrölä Erkki , Robert Charles , Dekemper Emmanuel
Published: March 2021

Twilight sky brightness spectral measurements are an inexpensive and effective way to observe enhancements of stratospheric aerosols. In this work, we present our observations of the volcanic cloud produced by the eruption of Raikoke volcano (Kuril Islands, 48°N, 153°E) above two distinct sites in South Caucasus and Western Europe, respectively: Tbilisi, Georgia (41° 43’ N, 44° 47° E) and Halle, Belgium (50° 44′ N, 4° 14′ E).

We present our dataset, which describes the evolution of the stratospheric aerosol in the period July 2019-December 2020. Stratospheric aerosol vertical extinction profiles were retrieved at 780 nm from spectral measurements of twilight sky brightness above both sites.

The first aerosols originating from Raikoke  were observed in the beginning of July above Halle and in August above Georgia. The layer maximum was mostly observed at 17 km above Georgia and at 10-17 km above Belgium until April-May 2020. Later, the volcanic cloud was observed sporadically until the end of 2020.
Ocean subduction dynamics in the Alps
Authors: Agard Philippe , Handy Mark
Published: March 2021

The Alps preserve abundant oceanic blueschists and eclogites that exemplify the selective preservation of fragments of relatively short-lived, small, slow-spreading North Atlantic-type ocean basins (here the ~400-700 km wide Alpine Tethys), whose subducting slabs reach down to the Mantle Transition Zone. Whereas none of the subducted fragments were returned during the first half of the subduction history, those exhumed afterwards experienced conditions typical of mature subduction zones worldwide. Sedimentary-dominated units were underplated intermittently, mostly at ~30-40 km depth, while mafic/ultramafic-dominated units subducted to ~80 km (In the W. Alps), whose protoliths had formed close to the continent, were offscraped from the slab only a few Ma before continental subduction. Spatiotemporal contrasts in burial and preservation of the fragments reveal how along-strike segmentation of the continental margin affects ocean subduction dynamics.
The relevance of small-magnitude earthquakes in detailing the spatiotemporal correlation between hydraulic fracturing related injection and seismicity
Authors: Kemna Kilian B. , Roth Marco P. , Wache Ricarda M. , Harrington Rebecca M. , Liu Yajing
Published: March 2021

Over the last decade, low-permeability tight shale formations in the Western Canada Sedimentary Basin (WCSB) have been extensively developed using hydraulic fracturing (HF) techniques for oil- and gas exploration. In the meantime, an increasing number of M3+ earthquakes (e.g., ML 4.5 11/30/2018 near Dawson Creek, and an Mw 4.6 08/17/2016 near Ft. St. John) has been associated with HF operations. By increasing the seismicity in areas of low historical seismicity, the relationship between operational parameters and the rate of fault activation needs to be fully understood to avoid economic losses due to operation shutdowns or damages caused by ground shaking.

As earthquakes follow a well-known power-law magnitude-frequency relation, standard earthquake catalogs are typically dominated by microearthquakes in quantity. However, they usually still miss a large number of earthquakes due to insufficient station coverage and/or limited duration of observation. The latter could also lead to an inadequate time window for detecting larger earthquakes, which results in uncertainties of the power-law relation parameters for a particular area.

Here, we enhance a local seismic catalog derived from a dense seismic network in the Kiskatinaw (Montney Formation) area in British Columbia, Canada, using a multi-station matched filter technique. The existing automated STA/LTA catalog > 8000 earthquakes contains earthquakes from July 2017 - July 2020 with manually revised phase arrivals from up to 25 broad-band stations, ranging between ML -0.6 to 4.5. Using all the ~8000 events from the initial catalog as templates, we detected > 40,000 additional earthquakes, lowering the magnitude of completeness Mc from ~1.3 to ~0.2. We observe a b-value of approximately 1, and the majority of events occurred between 1.0 - 3.0 km depth, where injection depths range from 1.5 - 2.5 km.  

In addition to the previously observed clustering of earthquakes around specific HF wells, we also observe ~8000 earthquakes with no apparent spatial (up to 5 km) or temporal (within two weeks of the reported HF stimulation) connection to HF operations. We estimate the contribution of the uncorrelated events to background seismicity rates. Furthermore, we detect earthquakes with templates related to HF operations, with spatial, but lacking temporal correlation to HF stimulation. Spatially correlated earthquakes with a no temporal correlation could highlight either areas with delayed induced seismicity (if following well stimulation) or areas with previous background seismicity (if preceding it). We will also show the correlation between background seismicity rates and cumulative injection rates and volumes of all wells within the study area.
A Material Point Method for Alpine Mass Movements
Authors: Cicoira Alessandro , Blatny Lars , Li Xingyue , Troilo Fabrizio , Kenner Robert , Gaume Johan
Published: March 2021

Gravitational mass movements pose a threat to the population of numerous mountainous regions around the globe. Climate change affects these processes and their related hazards by influencing their triggering, flow and deposition mechanisms, overall increasing the number of natural catastrophes. Numerical modelling is an essential tool for the analysis and the management of such hazards: it allows the quantitative description of the runout and pressure of rapid mass movements and may contribute to better understand the effects of climate change on their size, frequency, and dynamics. Several depth-averaged models are already operational and commonly applied by practitioners and scientists. Yet, a unified model able to simulate multi-phase cascading events, including their initiation, propagation, entrainment and finally impact on structures is still missing. Hence, more detailed models are  required to advance our understanding of the physics behind gravitational mass movements and ultimately to contribute improving hazard assessment and risk management.

Here, we present some preliminary results of the development of a hybrid Eulerian-Lagrangian Material Point Method (MPM) with finite strain elasto-plasticity to simulate in a unified manner: i) permafrost instabilities and failure initiation; ii) rock and ice avalanche dynamics; iii) solid-fluid interaction and phase transition from rock avalanches to debris-flows. In order to simulate the mechanical behaviour of rock and ice, we propose a Drucker-Prager softening constitutive law accounting for cohesion, internal and residual friction. We calibrate this constitutive law on the basis of state of the art laboratory experiments. The model is applied to synthetic slope geometries to evaluate their stability and investigate subsequent rock fragmentation processes. At a larger scale, dynamics simulations are compared against observations of full-scale process chains. In particular, we implement the two real-scale cases of the rock-avalanche from the Piz Cengalo (CH) and ice- and snow-avalanche from the Grandes Jorasses (IT). The 3D implementation of the model allows to accurately reproduce the initial conditions of an event and complex phenomena such as reported ballistic trajectories non adherent to the ground. Secondary releases due to the mass flow (such as snow or glacier-ice entertainment) and phase changes can be simulated realistically. We test the potential of the model in a broad range of settings and highlight the major gaps to be filled in the near future.
Impact of Climate Change on Apricot Yield in Turkey in the Near Future
Authors: Turp M. Tufan , An Nazan , Özertan Gökhan , Kurnaz M. Levent
Published: March 2021

Apricot (Prunus armeniaca L.) is one of the most important export crops in Turkey and Turkey is the leader for both fresh and dried apricots production in the world. Apricot can be grown in all regions of Turkey with climate and vegetation diversities, except in the Eastern Black Sea Region and in the high plateaus of the East Anatolian Region. Malatya is the main producer province, which has good ecological and soil conditions in terms of apricot cultivation with the highest quality in Turkey. However, it is possible to talk about irregularities and decreases in apricot yield due to climate change in the region. Therefore, this study aims to observe climate change impacts on apricot yield in the main producer city, Malatya. Hereunder, climate projections were made at a 10 km horizontal resolution for the future period of 2021-2050 under the “worst-case” scenario (RCP8.5) using a regional climate model (RegCM4.4) for Malatya province considering 13 sub-regions. A statistical model, panel data method-multiple regression model, is designed to observe the effect of climate change and variability on the yield. Results indicate that adverse impacts of climate change on biological development of apricot lead to production irregularities and significant losses in yield in Malatya.

 

Acknowledgement: This research has been supported by Boğaziçi University Research Fund Grant Number 16763.
How does the Arctic affect North Atlantic climate? Fresh perspectives on a long-standing question.
Authors: Oltmanns Marilena , Holliday N. Penny , Screen James , Evans D. Gwyn , Josey Simon A. , Moat Ben , Karstensen Johannes , Moore G. W. Kent
Published: March 2021

Recent decades have been characterised by amplified Arctic warming and increased occurrence of extreme weather events in the North Atlantic region. While earlier studies noticed statistical links between high-latitude warming and mid-latitude weather extremes, the underlying dynamical connections remained elusive. Combining different data products, I will demonstrate a new mechanism linking Arctic ice losses with cold anomalies and storms in the subpolar region in winter, and with heat waves and droughts over Europe summer. Considering feedbacks of the identified mechanism on the Arctic Ocean circulation, I will further present new support for the potential of Arctic warming to trigger a rapid change in climate.
The kingdom of Tonga devastated by a megatsunami in the mid-15th century
Authors: Lavigne Franck , Morin Julie , Patrick Wassmer , Olivier Weller , Taaniela Kula , Maea Ana V. , Kelfoun Karim , Mokadem Fatima , Paris Raphael , Malawani Mukhamad N. , Audrey Faral , Benbakkar Mhammed , Saulnier-Copard Ségolène , Vidal Céline M. , Tu’I’afitu Tu’I’ahai , Christopher Gomez , Kitekei’aho Fuka
Published: March 2021

The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its reconstruction is essentially based on legends left by oral tradition, and by archaeological evidence somehow difficult to interpret. By the fourteenth century, the powerful Tu'i Tonga kingdom united the islands of the Tongan archipelago under a centralised authority and, according to tradition, extended its influence to neighbouring island groups in the Central Pacific. However, some periods of deep crisis were identified, e.g. in the mid- 15th century, marked by an abrupt cessation of inter-archipelago migration on the deep seas in the Pacific, significant cultural changes, and a decrease in accessible natural resources. The origins of these disturbances are still debated, and are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring states. However, the hypothesis of a major natural disaster was never suggested up to now.

Drawing on a body of new evidence from sedimentary signatures and radiocarbon dating of charcoal and marine bioclasts, geomorphology, and sedimentology, in support of previously published archaeological data, we argue that the Tu’i Tonga kingdom was severely impacted by a megatsunami in the mid-15th century. We also discuss the likely sources of this event, which happened in an isolated region of the world before the European maritime “great discoveries”. This tsunami could be the source of vivid local myths that strongly suggest that a giant wave covered almost the entire island of Tongatapu at one time.
Impact of wind shear and stratification near the tropopause on baroclinic instability
Authors: Haualand Kristine Flacké , Spengler Thomas
Published: March 2021

Many weather and climate models fail to represent the sharp vertical changes of vertical wind shear and stratification near the tropopause. This discrepancy results in errors in the horizontal gradient of potential vorticity (PV), which acts as a wave guide for Rossby waves that highly influence surface weather in midlatitudes. In an idealised quasi-geostrophic model developed from the Eady model, we investigate how variations in vertical wind shear and stratification near the tropopause affect baroclinic growth. Comparing sharp and smooth vertical profiles of wind shear and stratification across the tropopause for different tropopause altitudes, we find that both smoothing and tropopause altitude have little impact on the growth rate, wavelength, phase speed, and structure of baroclinic waves, despite a sometimes significant weakening of the maximum PV gradient for extensive smoothing. Instead, we find that baroclinic growth is more sensitive if the vertical integral of the PV gradient is not conserved across the tropopause. Furthermore, including mid-tropospheric latent heating highlights that errors in baroclinic growth related to a misrepresentation of latent heating intensity are typically much larger than those associated with the correct representation of vertical wind shear and stratification in the tropopause region. Our results thus indicate that the correct representation of latent heating in weather forecast models is of higher importance than adequately resolving the tropopause.
On magma supply and spreading modes at slow and ultraslow mid-ocean ridges
Authors: Cannat Mathilde
Published: March 2021

The availability of magma is a key to understand mid-ocean ridge tectonics, and specifically the distribution of the two contrasted spreading modes displayed at slow and ultraslow ridges (volcanically-dominated, and detachment fault-dominated). The part of the plate divergence that is not accommodated by magma emplaced as gabbros or basaltic dikes is taken up by normal faults that exhume upper mantle rocks, in many instances all the way to the seafloor. 

Magma is, however, more than just a material that is, or is not, available to fill the gap between two diverging plates. It is the principal carrier of heat into the axial region and as such it may contribute to thin the axial lithosphere, hence diminishing the volume of new plate material formed at each increment of plate separation. Magma as a heat carrier may also, however, if emplaced in the more permeable upper lithosphere, attract and fuel vigorous hydrothermal circulation and contribute instead to overcooling the newly formed upper plate (Cochran and Buck, JGR 2001). 

Magma is also a powerful agent for strain localization in the axial region: magma and melt-crystal mushes are weak; gabbros that crystallize from these melts are weaker than peridotites because they contain abundant plagioclase; and hydrothermally-altered gabbros, and gabbro-peridotite mixtures, are weaker than serpentinites because of minerals such as chlorite and talc. As a result, detachment-dominated ridge regions that receive very little magma probably have a stronger axial lithosphere than detachment-dominated ridge regions that receive a little more magma. 

Because magma has this triple role (building material, heat carrier, and strain localization agent), and because it is highly mobile (through porosity, along permeability barriers, in fractures and dikes), it is likely that variations in magma supply to the ridge, in time and space, and variations in where this magma gets emplaced in the axial plate, cause a greater diversity of spreading modes, and of the resulting slow and ultraslow lithosphere composition and structure, than suggested by the first order dichotomy between volcanically-dominated and detachment-dominated spreading. 

In this talk I illustrate these points using results of recent studies at the Mid-Atlantic and Southwest Indian ridges.