bluuebunny/crossref_metadata_2025 huggingface dataset:
CHAPS: A Compact Hyperspectral Imager for Air Pollution Remote Sensing
Authors: Swartz William , Krotkov Nickolay , Lamsal Lok , Morgan Frank , Huang Philip , Linden Joseph , Levelt Pieternel , Veefkind Pepijn
Published: March 2020

Air pollution is responsible for ~7 million premature deaths every year.  Current and planned low Earth orbit and geostationary satellite instruments have long provided global surveys, revealing pollution characteristics and trends.  We need a robust, sustainable observing strategy, however, for measuring the distribution of air pollution at high spatial and high temporal resolution.  The Compact Hyperspectral Air Pollution Sensor (CHAPS) incorporates technologies enabling a sustainable approach to air pollution observation from space.  CHAPS is a hyperspectral imager using freeform optics in a form factor suitable for accommodation on a small satellite or hosted payload.  It will make measurements of air pollution at unprecedented spatial resolution from low Earth orbit (1 x 1 km2) and will characterize, quantify, and monitor emissions from urban areas, power plants, and other anthropogenic activities.  The compact size and relatively lower cost of CHAPS makes a constellation feasible for the first time, with unprecedented spatiotemporal sampling of global point pollution sources.  NASA recently funded the development of a CHAPS–Demonstrator (CHAPS-D), which will result in an airborne demonstration of a CHAPS prototype instrument.  CHAPS derives heritage from the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor, which uses a freeform mirror telescope.  Freeform optics has potentially huge advantages over traditional optical designs, including fewer optical surfaces, less mass and volume, and improved image quality.  CHAPS-D combines a radiometrically calibrated freeform hyperspectral imager (300–500 nm @ 0.5-nm resolution) with associated detector and payload electronics within the design constraints of a 6U CubeSat.  We present the measurement requirements and preliminary design of CHAPS-D.
Structure of the ultraslow-spreading Southwest Indian Ridge at 64°30’E from coincident multichannel and wide-angle seismic data
Authors: Corbalan Ana , Nedimović Mladen , Grevemeyer Ingo , Louden Keith , Watremez Lousie
Published: March 2020

Ultraslow-spreading oceanic ridges (<20 mm/yr) constitute about 35% of the global ridge system and yet the lithospheric structure that accretes at these spreading rates is little understood. At these ridges, the interplay between plate- and mantle-driven processes produces complex relationships between intermittent volcanic seafloor and extensive non-volcanic seafloor domains, with a subsurface structure that differs significantly from the traditional 3-layer crust topping the uppermost mantle that forms at faster-spreading rates. We present new constraints on the velocity and reflectivity structure of the oceanic lithosphere at the ultraslow-spreading Southwest Indian Ridge (SWIR) at 64°30’E. The eastern SWIR has a full-spreading rate of <14 mm/yr and represents a magma-poor endmember. In this area, broad serpentinized mantle domains are exposed with little interference of igneous rocks that can make their identification and geophysical characterization challenging. We use coincident wide-angle ocean bottom seismometer (OBS) and multichannel seismic (MCS) data collected during the SISMOSMOOTH 2014 survey along two long (~150 km) orthogonal profiles, one along the ridge valley (EW direction) and one across it (NS direction). We first run traveltime tomography using picks of first arrivals recorded by 16 OBS placed on the NS profile and 16 OBS on the EW profile. The computed models show that seismic velocities increase rapidly with depth, changing from 3.5-4 km/s at the seafloor to 7 km/s at 2-5 km and that the vertical gradient reduces for velocities greater than 7 km/s. We suggest that the changes in velocity with depth are related to changes in the degree of serpentinization and interpret the subsurface structure to be composed of highly fractured and fully serpentinized peridotites at the top with a gradual decrease in pore space and serpentinization to unaltered peridotites at depth. The NS velocity model shows greater lateral velocity variations than the EW profile, which indicates a more complex structure for the former. Next we perform MCS data analysis to produce reflection sections for the two profiles. Time-migrated sections are converted to depth using the velocities derived from the tomographic models. We observe steep south-dipping reflections around the highest topographic feature on the NS profile, coincident with a sharp lateral change in the velocities and a high vertical gradient in the velocity model, which we interpret as the seismic expression of an active axial detachment fault. Clear Moho arrivals are not identified either in the OBS or the MCS record sections, consistent with our interpretation of the subsurface being composed of a gradual transition from serpentinized peridotites to fresh mantle peridotites.
Integrating LCLM feedbacks into climate models: an emulator approach
Authors: Nath Shruti , Lejeune Quentin , Beusch Lea , Schleussner Carl , Seneviratne Sonia I.
Published: March 2020

The role of Land Cover and Land Management (LCLM) changes in shaping the climate has garnered increasing interest, particularly in light of its potential for climate adaptation and mitigation. Earth System Models (ESMs), however, have hitherto handled LCLM-climate interactions as a unidirectional process, lacking explicit treatment of LCLM-Climate feedbacks. Consequences of these feedbacks nevertheless hold social relevance, affecting agricultural systems, food provision and prices. Furthermore, LCLM can be linked to extreme climate events such as heat waves and drought, which in turn carry economic costs through loss in worker productivity. It is thus essential to integrate LCLM processes and their feedbacks into ESMs, in order to build consistent storylines for future development pathways that take into account their potential for adaptation and mitigation. Moreover, to ensure robustness in the detected LCLM signals, such integration should be done over a range of ESMs.

Emulators represent a computationally cheap but effective way of approximating ESMs. Here we outline an emulator approach to represent LCLM-Climate feedbacks based on a framework developed by Beusch et al. (2019). This framework provides spatially explicit data by translating annual global mean temperatures into local temperatures and can be extended to use for other relevant variables. The emulator is developed as part of the LAnd MAnagement for CLImate Mitigation and Adaptation (LAMACLIMA) project, and is trained on dedicated ESM simulations that isolate the effects of key land management practices focussed on by LAMACLIMA: irrigation, de/reforestation and wood. Variables considered include temperature, evapotranspiration, runoff, crop yields, carbon storage and heat stress. Besides providing spatially explicit representation of these variables, the emulator also allows flexibility in prescribing land-use scenarios under which their responses are explored.

Beusch, L. Gudmundsson, and S. I. Seneviratne: Emulating Earth System Model Temperatures: from Global Mean Temperature Trajectories to Grid-point Level Realizations on Land, doi: 10.5194/esd-2019-34, 2019 (accepted for ESD).
Spatiotemporal patterns of soil water stable isotope composition in forested headwater catchment
Authors: Moussa Adnan , Fabiani Ginevra , Klaus Julian
Published: March 2020

The vadose zone is a key component of the critical zone (CZ) and the interface of the atmosphere and the subsurface. A better understanding of critical zone hydrological processes is key for improving hydrological models and sustainable resource management. Isotopes of Hydrogen (2H) and Oxygen (18O) are a common tool to decipher hydrological processes in the CZ. However, there is still lack in understanding the spatiotemporal distribution of the soil water stable isotope composition (2H and 18O) at catchment scale. Until today, only a few studies evaluated long-term variability and spatial patterns. Here we present results of bi-weekly measurements of the soil water stable isotope over nine months. SWI composition were measured using direct vapour equilibration and accounted for different landscape elements (eight locations per campaign) in the forested Weierbach (~0.42 km2) experimental catchment in Luxembourg.

Preliminary results show that a strong similarity of δ18O depth profiles between different landscape elements at the same sampling date. However, after a snowmelt event we observed a much higher variability throughout the catchment likely from different melt, fractionation, and infiltration processes. The δ18O profiles throughout the landscape change consistently with time driven by a combination of rainfall and evaporation. Lc-excess data showed that soil water was experiencing kinetic evaporative fractionation in the top 30 cm of the soil throughout the year. The presented high frequent data on isotopic composition of soil pore water are useful to analyse spatial difference in vadose zone processes for better understanding soil-atmosphere interaction and flow processes. Eventually such data can be used for constraining spatially distributed hydrological models.
From Ashes to Fire: The Possibilities of the Phoenix Effect in Post-Disaster Lombok, Indonesia
Authors: Koopman Jop
Published: March 2020

The Lombok earthquake of August 2018 killed approximately 555, injured 1400, and displaced 353.000 people. With Indonesia being vulnerable to natural disaster due to its geographic location, events like these are not uncommon. However, this event was significantly different from the majority of disasters in the Indonesian archipelago. The difference pertains to how the communities researched in this thesis, coped with the adversity they had experienced and how they showed resilience in a unique way.

A disaster drastically ushers in a liminal period wherein its victims are forced to rethink certain aspects of social life, give meaning to what has happened, and determine how to rebuild society sustainably.

This thesis argues that going back to a pre-disaster state of society is not possible, due to the lived experiences during the disaster and aftermath. Instead of going back, the culture of response of the Indonesian government (and the NGOs and communities) on which this thesis is focused, started a process towards Dyer’s Phoenix Effect.

This thesis explores the cultural, social, and organizational changes in post-disaster Lombok, which make the occurrence of the Phoenix Effect likely. (1) Cultural changes constitute the explanations for the earthquake from different religious perspectives and the resurgence of traditionally embedded building strategies. (2) Social changes equate to the reinvention of gotong royong from being a state-philosophy to an embedded set of mutual help. (3) Organizational changes, signify biopolitics of disaster management of the Indonesian government, the role of NGOs, and the emergence of peoples’ initiatives in order to become more resilient.

This thesis concludes that the possibility of the Phoenix Effect is likely, if the involved communities can maintain their cultural, organizational, and social changes sustainably.
Evaluating fine-resolution, regional outputs of a variable resolution global climate model
Authors: Di Vittorio Alan , Xu Zexuan , Zhang Jie , Xin Xiaoge , Xu Hongmei , Xiao Chan
Published: March 2020

Climate models have been used to study water resources and regional hydrologic responses to climate change, but climate model outputs must be downscaled to provide relevant regional data. However, the accuracy of this regional data is limited by uncertainties across and within downscaling methods, uncertainty across global outputs, and discontinuities at downscaled boundaries. A new alternative to traditional downscaling is a variable resolution model that incorporates fine-resolution regions directly into a coarse-resolution, global climate simulation in order to capture contiguous dynamics across resolution boundaries. In this study, we used the Variable-Resolution Community Earth System Model (VR-CESM) to generate one-eighth degree (14 km) fine-resolution outputs for the western U.S. and eastern China from 1970-2006.

 

We focus our evaluation on precipitaiton, temperature, snow pack, solar radiation, and wind. We compare the model outputs with remote-sensing-based precipitation data, and both reanalysis and gridded weather station data for precipitation and temperature. VR-CESM generally has a cold bias in winter and a warm bias in summer in the western U.S., which compensate each other to reduce the annual bias. In eastern China, however, the sign of temperature biases are more consistent throughout the year with cold biases in the higher mountains and warm biases throughout most of the rest of the region. Precipitation biases are dependent upon reference data, and show slight overestimation in high mountain regions in both the U.S. and China with respect to gridded weather station data. Simulated snow cover in the western U.S. is reasonable compared to remote sensing data, but snow cover and snow water equivalent have larger biases when compared to reanalysis data. In eastern China there are widespread snow cover biases compared to remote sensing data. VR-CESM underestimates downward shortwave radiation to a greater degree in summer than in winter, and underestimates surface layer windspeed over mountains to a greater degree than in other areas. Comparison between VR-CESM and a coarser simulation (1-degree Beijing Climate Center model) shows reduced precipitation biases in the mountainous regions with finer resolution, indicating the value of variable-resolution modeling for reigonal studies.
Geo.KW - Coupling hydrothermal and infrastructure modeling at urban scale for an efficient use of shallow geothermal energy
Authors: Schramm Thilo , Heller Helmut , Böttcher Fabian , Halilovic Smajil , Odersky Leonhard , Davis Kyle , Hamacher Thomas , Mehl Mirjam , Zosseder Kai
Published: March 2020

To reduce anthropogenic climate change, the energy demand from all energy sectors has to be met by renewable energies, wherever possible.
Shallow geothermal energy usage, powered by green electricity, provides heating/cooling at a high level of efficiency, which is difficult to achieve with renewable energy alone.
We have created a coupling approach, which combines hydrothermal and infrastructure modeling at an urban scale to efficiently position shallow geothermal systems between existing power plants and conflicting groundwater usage, optimised by economical and ecological contraints.
We are using Pflotran, a finite volume Darcy-Richards model for our hydrothermal model.
The implementation of the energy infrastructure is done with urbs, a linear optimisation model for distributed energy systems.
We utilize preCICE, a coupling library for multi-physics simulations, for fully parallel peer-to-peer data exchange between these modeling domains.
Iterative optimization is meant to ensure the convergence of the fully coupled model.
South-westward Propagating Quasi-biweekly Oscillation over South-western Indian Ocean during Boreal Winter
Authors: Ghatak Sambrita , Sukhatme Jai
Published: March 2020

The Quasi-Biweekly Oscillation (QBWO), with a period between the synoptic scale and the Madden Julian Oscillation (MJO), is an important component of tropical intraseasonal variability (ISV). While this mode has received a lot of attention over India (during the summer monsoon) and South China sea region, less attention has been paid on South-western Indian Ocean (SWIO). Apart from improving our understanding of ISV, this mode is important in the SWIO during boreal winter as this is an active basin for tropical cyclones (TC), and the QBWO significantly influences TCs. Here we study details of the genesis of the QBWO, its propagation, vertical structure and evolution. The data used comprises of NCEP-NCAR and ERA-interim reanalysis and NOAA outgoing longwave radiation (OLR) from 2000-2010. A composite analysis based on 10-30 day filtered data during the boreal winter reveals a well-organized convectively-coupled wave-train pattern, namely the QBWO, over the SWIO. It emerges from south of the equator (5S), between 50-80E, and then propagates south-westward. The horizontal structure exhibits a slight southwest-northeast tilt, but mainly longitudinal elongation. After arriving Madagascar, the system shows more pronounced southward migration. Further, negative (positive) OLR anomalies are tightly coupled with a cyclonic  (anticyclonic) circulation at 850 hPa. In the end, the QBWO with associated anomalous convection dies down near 40S, between 40-70E. Overall, over this oceanic basin, the QBWO has a period of approximately 18 days, wavelength of about 5000-6000 km, a southward (westward) phase speed of 1.9 (2.7)°/day and a near zero group velocity. Near equator, the system emerges with an equivalent barotropic structure. When mature with strongest convection around 10-20S, the system becomes weakly baroclinic, with relative vorticity anomaly changing sign near 400 hPa, and in the dying phase after 30S, the QBWO becomes equivalent barotropic again. Finally, the centres of relative vorticity and vertical motion near the equator are consistent with the characteristics of equatorial Rossby waves, whereas the cyclonic circulation is tightly coupled with anomalous convection as the wave moves away from the equator.
A non-parametric procedure to assess the accuracy of the normality assumption for annual rainfall totals, based on the marginal statistics of daily rainfall: An application to NOAA-NCDC rainfall database
Authors: Ruggiu Dario , Viola Francesco , Langousis Andreas
Published: March 2020

In an effort to assess the accuracy of the normality assumption for annual rainfall totals (ART) in data-poor regions, we develop a non-parametric procedure based on the marginal statistics of daily rainfall. In doing so we start by using three goodness-of-fit metrics to conclude on the approximate convergence of the empirical ART distribution to a normal shape, and classify daily rainfall timeseries into Gaussian (G) and non-Gaussian (NG) groups. At a second step, we apply logistic regression analysis to identify the statistics of daily rainfall that are most descriptive of the G/NG classification. In the third and final step, we use a random-search algorithm to conclude on a set of constraints to classify ART samples based on the marginal statistics of daily rainrates. The analysis is conducted using 3007 daily rainfall timeseries from the NOAA-NCDC Global Historical Climatology Network (GHCN) database, and aims at developing a statistical tool towards informed decision making for water management purposes. The conducted analysis highlights that the Anderson-Darling (AD) test statistic is the most conservative one in determining approximate Gaussianity of ART samples (followed by Cramer-Von Mises and Kolmogorov-Smirnov), while daily rainfall timeseries with fraction of dry days in excess of 90% and skewness coefficient of positive rainrates that exceeds 5.92 deviate significantly from the normal shape. Further, our results indicate that continental climate exhibits the highest fraction of Gaussian distributed ART samples, followed by warm temperate, equatorial, polar, and arid climates.
Influence of the initial damage on fracture toughness and subcritical crack growth in a granite rock
Authors: D'Urso Salvatore , Pimienta Lucas , Passelègue François , Sandrone Federica , Vinciguerra Sergio , Violay Marie
Published: March 2020

Fracture mechanics is an important tool to assess the slope stability, since this approach offers a methodology to study the fracture stress field in the neighborhood of the joint tips and accurately predict propagation of the joints over time. While the fracture toughness of material has been extensively studied in the past, low interest was given to the influence of initial damage on the subcritical crack growth, despite of its relevance to assess long term slope stability. Here we report new experimental results that address this question.

Starting from the real case of unstable rock mass of “Madonna del Sasso” (Colombero et al., 2015), a series of Cracked Chevron Notched Brazilian Disc (CCNBD) (Fowell, 1995) specimens were failed in a standard Mode I tensile test to investigate the effects of thermal damage on fracture toughness and subcritical crack growth on samples of granite of Alzo.

The degree of initial damage was imposed using slow heat treatment (1°C/min) up to 100, 200, 300 and 400°C, to emulate different levels of rock degradation. The samples were equipped with strain gauges close to the tips of the notch, an extensometer for the Crack Mouth Opening Displacement (CMOD) and twelve Acoustic Emission recorders.

Our results show that fracture toughness decreases with increasing thermal damage, in agreement with previous studies (Nasseri, Schubnel, & Young, 2007). The fracture toughness of undamaged granite is 1.04 MPa m1/2, but 0.65 MPa m1/2 after treatment up to 400°C.

Subcritical crack growth behaviour has been studied for samples treated from 100°C up to 400°C through creep tests on CCNBD specimens. The overall effect of heat treatment is to increase the crack growth rate in granite for a given stress intensity factor. The slopes of stress intensity factor versus crack velocity curves are sensitive to modifications of initial damage’s degree. Trend drops substantially with increase of the temperature of the heat treatment. This shows a substantial increase of the internal damage index n, and a decrease of the time to failure of the CCNBD specimens.

The study highlights the importance of considering both the time-dependent slope behaviour and effects of rocks internal damage, since these conditions could lead to an unexpected premature failure.
A multi-temporal inventory for constraining earthflow source-to-sink pathways in the Sillaro River basin, Northern Apennines
Authors: Pittau Sharon , Berti Matteo , Daniele Giovanna , Pizziolo Marco , Brardinoni Francesco
Published: March 2020

In mountain environments, landslide sediment supply is one of the main factors that can affect fluvial morphodynamics. In settings underlain by clay-rich lithologies, where earthflows are the dominant agents of hillslope sediment transfer, limited quantitative information is available on the contribution of these processes to the sediment budget. This is a critical aspect both for addressing basic scientific questions on landscape evolution, as well for tackling more applied issues on river sediment management.

This study focuses on the mountain portion of the Sillaro River basin (138 km2), a fluvial system underlain by argillites and siltstones of the Ligurian domain, Northern Apennines (Italy). Here, earthflows are the most common landslide type. Through the compilation of a multi-temporal earthflow inventory (1954-2019), we aim to: (i) characterize earthflow source-to-sink sedimentary pathways, with special reference to sediment delivery to ephemeral and perennial streams; (ii) explore possible litho-topographic controls on earthflow size, frequency and recurrence; (iii) examine historical trend of earthflow activity in relation to rainfall variability and land use changes. Finally, the high and extended temporal resolution of the inventory, will offer the opportunity to test how relevant information could complement the existing inventory of the Emilia-Romagna region, for evaluating earthflow hazard and risk potential.

Data collection entailed inspection of 12 sequential aerial photo sets (1954, 1969, 1976, 1988, 1996, 2000, 2006, 2008, 2011, 2014, 2016, and 2018), through which earthflows were classified and mapped in GIS environment. This remotely-based activities were complemented by confirmatory field visits on a subset of most recent events. Overall, we have mapped a total of 506 earthflows, which collectively extend over an area of 4.1 km2.

Preliminary results show that earthflow size (i.e., total disturbed area) ranges from 400 m2 to 98000 m2, with frequencies peaking around 10000 m2. In terms of source-to-sink pathways, we find that earthflows chiefly tend to deliver sediment to ephemeral gully channels (61%) and perennial tributaries (25%). Whereas, 5% of the events remain on the slopes, and another 5% are buffered by roads and similar anthropogenic barriers. Only a very limited proportion of earthflows (4%) makes it directly to the Sillaro River main stem.

This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.
Regional trends in flood quantiles across Europe between 1960 and 2010
Authors: Bertola Miriam , Viglione Alberto , Lun David , Hall Julia , Blöschl Günter
Published: March 2020

Evidence of past flood regime changes in Europe has been shown by several local and regional trend detection studies. These studies typically analysed changes in the mean or median flood. In this work, we investigate regional trends in the 2-year flood and in the 100-year flood. Additionally, it is of interest to investigate the effect of catchment scale on the changes in time of the selected flood quantiles. We analyse 2370 flood records, selected from a newly available pan-European flood database, with record lengths of at least 40 years over the period 1960-2010 and catchment areas ranging from 5 to 100 000 km2. In order to estimate the regional trend in flood quantiles, a non-stationary regional flood frequency approach is used, consisting of a regional Gumbel distribution whose parameters are allowed to vary with time and with catchment area. A Bayesian Markov Chain Monte Carlo (MCMC) approach is used for parameter estimation. With a spatial moving window approach, regional trends of the selected flood quantiles, and the related uncertainties, are estimated and compared across Europe, for hypothetical catchment sizes ranging from 10 to 100 000 km2. Distinctive patterns of flood regime change are identified for large regions across Europe which depend on flood magnitudes and catchment areas. The resulting trends in flood magnitudes are positive (with the exception of very large catchments) in Atlantic catchments, where the magnitude of trends decreases with increasing catchment size and for bigger return periods. In Mediterranean catchments the regional trends are negative, with small floods experiencing a stronger decrease than large floods. In Eastern European catchments, the regional trends are clearly negative, with larger magnitudes (in absolute value) for larger catchments; they do not appear to vary substantially with the return period.
Inferring seismic hazards from a new 1:25,000 scale map of active and potentially-active continental faults in Chile
Authors: Melnick Daniel , Maldonado Valentina , Contreras Martin , Jara-Muñoz Julius , Cortés-Aranda Joaquín , Astudillo Luis , Martínez José Miguel , Tassara Andrés , Strecker Manfred
Published: March 2020

Most of the seismic hazard along subduction zones is posed by great tsunamigenic earthquakes associated with the interplate megathrust fault. However, crustal faults are ubiquitous along overriding continental plates, some of which have been triggered during recent megathrust earthquakes. In Chile, the 2010 Maule earthquake (M8.8) triggered a shallow M7 earthquake on the Pichilemu fault, which had not been mapped and was unknown. In fact, M~7 earthquakes have recently occurred along unknown faults in California and New Zealand, emphasizing the need for better and more detailed mapping initiatives. A first step towards a synoptic assessment of seismic hazards posed by continental faults at the national level is mapping at a homogeneous scale to allow for a systematic comparison of faults and fault systems. Here, we present the first map of active and potentially-active faults in Chile at 1:25,000 scale, which includes published studies and newly-identified faults. All the published faults have been re-mapped using LiDAR and TanDEM-X topography, where available. Using different scaling relations, we estimate the seismic potential of all crustal faults in Chile. For specific faults where we have conducted paleoseismic and tectonic geomorphic field studies (e.g., Liquiñe-Ofqui, El Yolki, Mesamavida, and Pichilemu faults) we provide new estimates of slip rate, recurrence interval, and deformation style. We propose a segmentation model of continental faults systems in Chile, which are associated with distinct morphotectonic units and have predominant kinematics and relatively uniform slip rates. Using stress transfer models, we explore the potential feedbacks between upper-plate deformation and the megathrust seismic cycle.
A 34 Year Assessment of Surface and Top-of-Atmosphere Radiative Fluxes from the NASA’s GEWEX Surface Radiation Budget Release 4 Integrated Product
Authors: Stackhouse Paul , Cox Stephen , Mikovitz J. Colleen , Zhang Taiping
Published: March 2020

The NASA/GEWEX Surface Radiation Budget (SRB) project is finalizing a 3-hourly shortwave and longwave surface and top-of-atmosphere radiative fluxes for a 34-year period from July 1983 through June 2017. The new Release 4 Integrated Product (IP) uses the newly recalibrated and processed ISCCP HXS product as its primary input for cloud and radiance data, replacing ISCCP DX with a ninefold increase in pixel count (10 km instead of 30 km).  This first version retains a 1°x1° resolution for intercomparison against previous versions and other data sets such as CERES. ISCCP also provides an atmospheric temperature and moisture dataset known as nnHIRS which we use and discuss radiative flux sensitivities to in this presentation.  In addition to the input data improvements, several important algorithm improvements have been made since Release 3. These include recalculated SW atmospheric transmissivities and reflectivities yielding a somewhat less transmissive atmosphere. Ocean albedo and snow/ice albedo are also improved from Release 3. Total solar irradiance is now variable consistent with SORCE measurements. The LW code has been updated to improve the optical property treatment for clouds, particularly ice clouds, and aerosols are included in this version.  The variable aerosol composition are specified using a detailed aerosol history from the Max Planck Institute Aerosol Climatology (MAC).  Seasonally dependent spectral surface emissivity maps are now also included.  In this presentation, we analyze the new SW and LW SRB datasets, comparing them to the previous Release 3, BSRN, GEBA and PMEL surface measurements, and ERBE and CERES satellite datasets.  For surface flux validation besides ensemble comparisons, we show the variability of SRB vs surface measurements from BSRN beginning in 1992 and GEBA from 1983.  For the early period, comparison of top-of-atmosphere flux variability is made to latest version of ERBE fluxes.  For the latter period, we provide comparisons to CERES SYN1Deg and EBAF datasets for a benchmark.  Long-term changes in the surface radiation budget components and cloud radiative effects are shown and discussed relative to CERES and surface measurements.   An assessment of long-term changes are made including an assessment of uncertainties due to satellite artifacts.
A conceptual framework for the study of bank erosion in large rivers: insight from the St. Lawrence River, Canada
Authors: Bernier Jean-François , Chassiot Léo , Lajeunesse Patrick
Published: March 2020

The St. Lawrence River forms a major socio-economic and commercial axis in eastern North America, and one of the most populated cold rivers worldwide. Its upstream section, the fluvial corridor, located between the Quebec-Ontario border and Quebec City (QC, Canada), concentrates most of the human facilities and activities. Over the past decades, climate change and increased human pressures on the banks have deeply altered the natural hydro-sedimentary dynamics within this corridor. Yet, the environmental and socio-economic consequences have long been overlooked. The recent flooding events of 2017 and 2019 have highlighted the vulnerability of river habitats and infrastructures, underlining the need to integrate bank erosion hazard to ensure sustainable management of riparian areas and to adapt land-use planning strategies.

A research program started in late 2017 allowed a cross-science collaboration between academic scientists, the Government of Québec, environmental organizations and agencies, municipalities as well as concerned citizens. This program aims at characterizing riverbank types within the fluvial corridor and at assessing erosion hazard, processes, and controlling factors over more than 4000 km of riverbanks. We combined field surveys, remote sensing (LiDAR, aerial photographs) and crowdsourcing data to develop a geospatial database for local stakeholders.

We present the conceptual framework, methods and main results for riverbanks classification and erosion hazard assessment, and discuss the challenges posed by the study of large rivers. We emphasize on issues related to anthropogenic stressors and specificities (river ice, maritime traffic) of the St. Lawrence River. This is the first time, to our knowledge, that the subject of bank erosion has been assessed with such high resolution, but also with the same method, on an ice-affected river as large and diverse as the St. Lawrence.
Mathematical simulation of melting mountain glaciers
Authors: Belozerov Egor , Rets Ekaterina , Popovnin Viktor
Published: March 2020

Freshwater shortage is one of the global problems of our time. Glaciers contain a large amount of freshwater on the Earth. Nowadays mountain glaciation is decreasing almost throughout the world (Panov, 1993; Duethmann et al., 2016; Fausto et al. 2016). This effect leads to an increase in the water content of mountain rivers, but also cause a decrease in glaciers freshwater reserves (Trenberth et al., 2007; Sorg et al., 2012). This impact is already felt in the arid regions of our planet. Recently in Central Asia was observed a shortage of water resources. According to the estimates, the total area and mass decrease of the Tien Shan glaciers, from 1961 to 2012, amountes to 18 ± 6% and 27 ± 15% (Farinotti et al., 2015). The degradation of the area and volume of the Tien Shan glaciers, in the period from 1961 to 2012, was 18 ± 6% and 27 ± 15% (Farinotti et al., 2015). About 15% of the runoff in the Republic of Kyrgyzstan is fed by glacial nutrition, but this contribution may even be 1.5-3 times greater during the warm season (Dikikh et al., 1995; Kemmerikh, 1972). The average annual rivers runoff in the Republic of Kyrgyzstan increased from 47.1 km3 (~ 1947–1972) to 50 km3 (1973–2000) (Mamatkanov et al., 2006). The representative glacier of the Central Caucasus - Dzhankuat can serve as an example of depletion of freshwater in the glaciers of the Caucasus. Over the past decades, since 1974, the Dzhankuat glacier has lost large volumes - almost twice, and at the time of 2013 it is equal to 0.077 ± 0.002 km3. From 2006 to 2015 the volume of the Dzhankuat glacier decreased by 25%, as a consequence, there is an increase in the rate of degradation (Lavrentiev et al., 2014).

In this article is presented mathematical simulation, which allows to solve a number of problems. One of the most important problem is the calculation of the water supply into the river network because of snow and ice melting in mountain areas. Weather conditions are taken into account in the simulation calculation of snow and ice melting over the entire glacier surface.

This work is supported by the Presidential Russian Federation grant №MK-2936.2019.5
Probabilistic identification of rockfall source areas: an example from El Hierro island (Canary Island, Spain)
Authors: Rossi Mauro , Sarro Roberto , Reichenbach Paola , Mateos Rosa María
Published: March 2020

Rockfalls are the most frequent and dangerous instability phenomena in mountainous areas, causing high economic and social damages. Rockfalls are triggered by complex instability mechanisms and the source areas are controlled by environmental factors like geology, the presence of discontinuities and slope angle. Modeling rockfall phenomena is complex and requires diversified input including parameters controlling the boulders trajectories and the source areas identification.

In the Canary Islands, the steep topography and the geological complexity influence the activation of slope dynamics and the occurrence of slope failures. In particular, rockfalls are very common and they represent a major threat to society, costing lives, disrupting infrastructures and destroying livelihoods. In 2011 the volcanic crisis in El Hierro Island triggered numerous rockfalls that affected the road network causing a great social alarm.

After the recent event, we have attempted to identify rockfall source areas using different approaches including probabilistic modeling. The probabilistic approach applies a combination of multiple statistical models and requires a map of the observed source areas as dependent variable and a set of thematic information as independent variables (e.g., morphometric parameters derived from DTM, lithological information that considers the mechanical behavior of the rocks). For the purpose, we have identified various scenarios selecting different training and validation zones and evaluating for each scenario the associated errors. The maps resulting from the models, provide for the whole El Hierro Island, the probability of a pixel being a source area and can be used as input for the rockfall modeling.
Earthquake-earthquake triggering in natural swarms and fluid-induced seismicity
Authors: Karimi Kamran , Davidsen Joern
Published: March 2020

Aftershock cascades and aftershock zones play an important role in forecasting seismic activity in both natural and human-made situations. While their behavior including the spatial aftershock zone scaling has been the focus of many studies in tectonic settings finding, for example, long-range earthquake-earthquake triggering in the near-field, this is not the case in situations where the seismic activity is primarily driven by fluids and the diffusion of excessive pore pressure. Here, we probe three different seismic settings that are believed to be influenced by fluid diffusion. The natural swarm in i) the Long Valley Caldera and the suspected swarms in ii) the Yuha Desert, both located in California, and associated earthquake-earthquake triggering behavior are compared against induced seismicity related to large scale wastewater disposal in iii) Oklahoma and southern Kansas. All settings exhibit a significant amount of event-event triggering highlighting the importance of secondary processes for the overall seismicity. We find an almost identical temporal event-event triggering behavior including the Omori-Utsu relation and the associated productivity relation. In terms of the spatial triggering density, both cases i) and iii) show a rapid decay beyond their rupture length. This proves that narrow spatial “aftershock” zones are not specific to induced seismicity but also occur in natural settings. Typical of most tectonic settings, a relatively long-range behavior is observed in case ii) suggesting that fluid migration might not be the dominant driving mechanism of the seismic activity and/or that the underlying structure of the fault network may control the secondary earthquake-earthquake triggering and its spatial evolution.
Numerical benchmark study for flow in highly heterogeneous aquifers
Authors: Suciu Nicolae , Alecsa Cristian Daniel , Boros Imre , Frank Florian , Knabner Peter , Nechita Mihai , Prechtel Alexander , Rupp Andreas
Published: March 2020

Solving the flow problem is the first step in modeling contaminant transport in natural porous media formations. Since typical parameters for aquifers often lead to advection-dominated transport problems, accurate flow solutions are essential for reliable simulations of the effective dispersion of the solute plumes. The numerical feasibility of the flow problem for realistic parameters accounting for the heterogeneity of the aquifer and the spatial scale of the transport problem is addressed in a benchmark study.

The study aims to investigate the accuracy and the convergence properties of several numerical approaches for simulating steady state flows in heterogeneous aquifers. Finite difference, finite element, discontinuous Galerkin, spectral, and random walk methods are tested on two-dimensional benchmark flow problems. The heterogeneity of the aquifer system is described by log-normal hydraulic conductivity fields with Gaussian and exponential correlation structures. For given integral scale both correlation models predict the same effective coefficients, but they pose very different numerical challenges: while the Gaussian correlation ensures the sample-smoothness of the fields, the exponential correlation does not fulfil the theoretical requirements and the numerical representations of the samples are rather noisy.

Realizations of log-normal hydraulic conductivity fields are generated with a Kraichnan algorithm in closed form as finite sums of random periodic modes, which allow direct code verification by comparisons with manufactured reference solutions. The quality of the methods is assessed for increasing variance of the log-hydraulic conductivity fields, which quantifies the heterogeneity, and for different numbers of random modes, which account for the spatial scale of the simulation. Experimental orders of convergence are calculated from successive refinements of the grid. The numerical methods are further validated by comparisons between statistical inferences obtained from Monte Carlo ensembles of numerical solutions and theoretical first-order perturbation results.

It is found that while for Gaussian correlation of the log-conductivity field all the methods perform well, in exponential case their accuracy deteriorates and, for large variance and number of modes, the benchmark problems are practically not solvable with reasonably large computing resources, for all the methods considered in this study.
Soil carbon dynamic after freezing/thawing and drying/wetting in a temperate forest soil: Dual labeling of 13C and 14C
Authors: Nájera Francisco , Dippold Michaela , Boy Jens , Seguel Oscar , Köster Moritz , Stock Svenja , Merino Carolina , Kuzyakov Yakov , Matus Francisco
Published: March 2020

Temperate forests in Chile have experienced increasing temperatures and extreme climatic events, such as severe drought and short winters in unique Araucaria araucana forest in Nahuelbuta National Park. Therefore, it is relevant to understand the impact of drying and rewetting (D/R) or freezing and thawing (F/T) on SOM turnover in these ecosystems. Particularly important is the destabilization of soil organic matter (SOM) by microbial activity, which is highly heterogeneous and influenced by soil properties and water cycles. Drying and rewetting or F/T cycles accelerate particulate organic matter (POM) decomposition by aggregate disruption, thereby, decreasing carbon (C) availability for soil microorganism. We hypothesized that frequent D/R and F/T cycles release labile organic C locked away in the aggregates for microbial consumption. We assumed that a repeated number of D/R and F/T cycles enhance the preferential C utilization of fresh organic substrate. In the present study an incubation experiment was conducted for 27 days to assess the effect of F/T (-18 ºC to room temperature) and D/R (-500 kPa to 33 kPa, field capacity) cycles on labelled 14C glucose and 13C lignocellulose decomposition, soil aggregates size and POM fractions distributions. CO2 efluxes and priming effect (PE), i.e. the turnover acceleration or retardation of native C mineralization, C use efficiency (CUE) and C allocation in soil aggregate classes as POM-light, POM-occluded and heavy fractions were also determined. Labelled glucose was mainly allocated in macro (> 250 mm) and microaggregates (< 250 mm) as part of the POM-light fraction. In contrast, labelled lignocellulose was allocated in microaggregate in the POM-occluded and heavy fraction. CUE was similar amongst all treatments. The PE was negative in soil with and without cycles and it was much more pronounced (-125 mg C kg-1 soil) for F/T cycles than D/R (-50 mg C kg-1 soil) at the end of incubation. The C:N ratio of soil following mining theory is further discussed. We conclude that D/R cycles clearly retarded the native C mineralization by preferential use of labelled 13C-lignocellulose, while F/T cycles led to preferential use of 14C-glucose.
Surface Deformation in Northeast Italy by using time series InSAR techniques with Sentinel-1 data
Authors: Areggi Giulia , Tolomei Cristiano , Bonini Lorenzo , Pezzo Giuseppe
Published: March 2020

Geodetic data provide useful information on surface deformation over long period of time. Applying time series methods to geodetic data, several phenomena were studied. In particular, the potentials of geodetic data were exploited to detect and measure slow tectonic signals such as interseismic strain accumulation. During the interseismic period, when the faults are locked, an accumulation of deformation can occur in response to active tectonic stresses. Considering that such energy can be released through earthquakes, the estimation of surface deformation and the long-term strain rate reveals itself a useful approach for seismic hazard investigations. In this study, we used remote sensing Synthetic Aperture Radar data to evaluate the ground deformation in the Southeastern Alps (Northeastern Italy), an area characterized by an active convergent regime (Adria plate motion is ~ 2mm/yr) as well as several active tectonic structures. We used SAR images provided by Sentinel-1A/B satellites spanning the 2015-2019 temporal interval by applying the multi temporal Small Baseline Subset Interferometry (SBAS) technique. The method is based on a combination of a large number of interferograms characterized by small temporal and geometric baseline in order to reduce decorrelation effects and increase the spatial coverage over the area of interest. The outcomes consist of displacement time series and a mean ground velocity map for each coherent pixels with respect to the satellite Line-of-Sight (LoS). Some detected patterns can be attributed to subsidence phenomena, affecting the plain in the area under analysis, and due to the compaction of the sediments.