bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic matter in black sand soils related to alkyl carbon and organo-mineral structures at the microscale
Authors: Schweizer Steffen A. , Lugato Emanuele , Höschen Carmen , Kögel-Knabner Ingrid
Published: March 2021

Agricultural sandy soils with high organic matter (OM) contents are generally unexpected under the current paradigm of organic matter formation and stabilization. These so-called black sand soils occur in North-Western Europe and have been related to historical heathland vegetation. The properties and mechanisms of the high OM sequestration in these soils are not clear as they exceed common observations of OM stored in coarse-textured soils. In this study, we analyzed a subset of samples with ‘black sand’ properties from the European soil database “Land Use/Cover Area frame statistical Survey” (LUCAS). Through particle size fractionation, we isolated the fine fraction <20 µm which contained, on average, 55 % of the total soil organic carbon (OC), in only 8 % of the corresponding soil mass. The fine fraction <20 µm contained 301 mg OC g-1 with a C:N ratio of 17.4 on average and was positively correlated with the bulk soil OC. The characterization of OM composition in the fine fractions by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy revealed that the share of alkyl C increased with OC concentrations whereas O/N-alkyl C decreased. To analyze the distribution of OM at the microscale, we analyzed five samples from the <20 µm fraction containing a gradient of 245-378 mg OC g‑1 with nanoscale secondary ion mass spectrometry (NanoSIMS) at a spatial resolution of 120 nm. These microscale measurements revealed fine mineral particle structures associated with heterogeneously distributed OM. Using image analysis, we found that the proportion of OM-dominated area (indicated by 12C2- and 26CN-) increased from 52 to 80 % on average with increasing OC concentration of the fine fractions. A majority of OM-dominated area was correlated with higher 42AlO- counts, which might suggest a preferential co-localization. In turn, the particle area which was dominated by minerals (indicated by 16O‑, 28Si‑, 42AlO‑ and 72FeO‑) contained less Al and more Si. This shows that the more alkylated and OM-rich fine fractions are related with distinct patterns of organo-mineral structures at the microscale.
Pore-scale Mixing and the Evolution from Anomalous to Normal Hydrodynamic Dispersion
Authors: Dentz Marco , Puyguiraud Alexandre , Gouze Philippe
Published: March 2021

Transport of dissolved substances through porous media is determined by the complexity of the pore space and diffusive mass transfer within and between pores. The interplay of diffusive pore-scale mixing and spatial flow variability are key for the understanding of transport and reaction phenomena in porous media. We study the interplay of pore-scale mixing and network-scale advection through heterogeneous porous media, and its role for the evolution and asymptotic behavior of hydrodynamic dispersion. In a Lagrangian framework, we identify three fundamental mechanisms of pore-scale mixing that determine large scale particle motion: (i) The smoothing of intra-pore velocity contrasts, (ii) the increase of the tortuosity of particle paths, and (iii) the setting of a maximum time for particle transitions. Based on these mechanisms, we derive an upscaled approach that predicts anomalous and normal hydrodynamic dispersion based on the characteristic pore length, Eulerian velocity distribution and Péclet number. The theoretical developments are supported and validated by direct numerical flow and transport simulations in a three-dimensional digitized Berea sandstone sample obtained using X-Ray microtomography. Solute breakthrough curves, are characterized by an intermediate power-law behavior and exponential cut-off, which reflect pore-scale velocity variability and intra-pore solute mixing. Similarly, dispersion evolves from molecular diffusion at early times to asymptotic hydrodynamics dispersion via an intermediate superdiffusive regime. The theory captures the full evolution form anomalous to normal transport behavior at different Péclet numbers as well as the Péclet-dependence of asymptotic dispersion. It sheds light on hydrodynamic dispersion behaviors as a consequence of the interaction between pore-scale mixing and Eulerian flow variability. 
Constructing an NOx Hourly Emissions Inventory for the Greater London Area from Open-Source Data.
Authors: Kiriakidis Pantelis
Published: March 2021

The study aims to re-create an NOx emission inventory for the greater London area on an hourly temporal resolution using mostly open-source data. London was chosen as the target location due to the vast amount of data accessible to the public. The main objective of the study is to create pattern formations of intraday variations for NOx emissions and enable predictions of increased temporal accuracy. The inventory focuses on the three most significant emitting sectors; non-road mobile machinery (NRMM), domestic gas and road transport, accounting for 10%, 13% and 45% of the 2016 total budget respectively. The study makes use of a bottom-up approach and compares the results with the annual NOx values stated in the London Atmospheric Emissions Inventory. 

The estimation of road transport emissions makes use of recorded annual vehicle kilometres broken down per borough and per type of vehicle, the registered London vehicle stock and the estimated probability of a vehicle to be on-road per hour of the day depending on the day and month. The aforementioned data are provided by the Department for Transport and the Digest UK Energy Statistics databank. Furthermore, a traffic index specified by the TomTom traffic dataset is used to identify an hourly average vehicle speed per road type and then is used alongside speed-based emission factors published by Transport for London to determine the geospatial specific emissions per vehicle category and per kilometre travelled. Formulation of domestic gas emissions employs real-time data of gas demand in kWh on 15-minute intervals sourced from the National Grid. The data was used alongside characteristics of the local boiler stock provided by Aether and was spatially distributed using energy efficiency ratings of households in each borough, provided by Digest UK Energy Statistics. Estimating emissions from NRMMs made use of the total number of machineries registered for operation in London since 2015, obtained through the King’s College NRMM registry. The machineries were categorised depending on horsepower and Euro standard as published by the 2009 EMEP/EEA Guidebooks, from which the associated NOx emissions factors were taken from. In addition, emissions were geographically distributed by prorating NRMMs according to the registered construction projects per borough. The discrepancies observed between the modelled and the London Atmospheric Emissions Inventory values was 5.9% for domestic gas emissions, 11.2% for NRMMs and for the vehicle categories; diesel cars, petrol cars, HGVs and LGVs, it differed by -2.0%, 7.0%, -3.0% and 14.2% respectively. 
Wind inference by a real-time global ocean weather sensor network
Authors: Houghton Isabel , Smit Pieter , Janssen Tim
Published: March 2021

A distributed sensor network of several hundred free-drifting, real-time marine weather sensors was deployed beginning in early 2019 initially focused in the Pacific Ocean and expanding globally. The Spotter buoys used in the network represent a next generation ocean weather sensor designed to measure surface waves, wind, currents, and sea surface temperature. Despite the demand for better weather forecasts and climate data in our oceans, direct in situ measurements of marine surface weather (waves, winds, currents) remain exceedingly sparse in the open oceans. Due to the large expanse of our oceans, distributed paradigms are necessary to create sufficient data density at global scale, similar to advances in sensing on land and in space. Here we discuss findings from this long-dwell open ocean distributed sensor network, specifically significant wave height accuracy and advancements in wind inference from the wave spectrum. The delivery of full-spectra data by the buoys beginning in 2020 facilitated improved calculation of surface wind derived from wind-sea interaction dynamics. Through triple-collocation analysis, we are able to determine errors in collocated satellite-derived observations and model estimates for both wind and waves. Altogether, we present a completely new open ocean weather data set, characterize the data quality against other observations and models, and further utilize the data collected to improve upon wind inference algorithms. In this work, we demonstrate the broad value for ocean monitoring and forecasting that can be achieved using large-scale distributed sensor networks in our oceans.
Towards machine learning for the estimation of wildfire risk from weather and sociological data
Authors: Pilot Jonas , Bui Thanh Binh , Boers Niklas
Published: March 2021

Estimating the probability of a wildfire occurring at a specific location on a given day comes with the challenge that it not only depends to a high degree on weather conditions and soil moisture, but also on the presence of an ignition source [1]. A commonly used index to assess wildfire risks is the Canadian Fire Weather Index [2], which does, however, not model the presence of an ignition source. 

We develop a machine learning model which discriminates between (1) the probability of a wildfire occurring given an ignition source, and (2) the probability of an ignition source being present, and inferences both. We first demonstrate the performance of our approach by estimating these probabilities on simulated data. With these simulations, we also assess the robustness of our model to machine learning-related challenges that arise with wildfire data, such as extreme class imbalance and label uncertainty. We then show the performance of our model trained on satellite-derived global wildfire occurrences between 2001 and 2017. The dataset FireTracks, which includes a comprehensive record of wildfire occurrences [3], is used as ground truth. Input features include weather data (ERA5 [4]) and population densities (GPW4 [5]). Finally we compare wildfire risk ratings computed with the Canadian Fire Weather Index to the probabilities estimated by our model.

References
[1] K. Rao et al., SAR-enhanced mapping of live fuel moisture content, Remote Sensing of Environment, 2020. 
[2] R. D. Field et al., Development of a Global Fire Weather Database. Natural Hazards and Earth System Sciences, 2015. 
[3] D. Traxl, FireTracks Scientific Dataset, 2021. (https://github.com/dominiktraxl/firetracks) 
[4] H. Hersbach et al., ERA5 hourly data on single levels from 1979 to present, Copernicus Climate Change Service (C3S) Climate Data Store (CDS), 2018. 
[5] Center for International Earth Science Information Network - CIESIN - Columbia University, Gridded Population of the World, Version 4 (GPWv4): Population Density, NASA Socioeconomic Data and Applications Center (SEDAC), 2016.
The impact of upper tropospheric temperature change on tropical cyclone
Authors: Eguchi Nawo , Kobayashi Kenta , Ito Kosuke , Nasuno Tomoe
Published: March 2021

We evaluate the impact of temperature at the upper troposphere and lower stratosphere (UTLS) on the tropical cyclone (TC) generation and its development by using the nonhydrostatic atmosphere-ocean coupling axisymmetric numerical model [Rotunno and Emanuel, 1987; Ito et al., 2010]. In the case of cold simulation at UTLS, the maximum wind and the minimum sea level pressure are increased and decreased than the control run, respectively. The magnitude of intensity change is the approximately 4 times larger than the change estimated from the MPIs (Maximum Potential Intensity [Bister and Emanuel,1998; Holland, 1997]). Further, during the development phase, the cold air mass intrudes to the middle troposphere from the upper troposphere at the center of TC, which is not seen in the warm case, leading the atmosphere unstable and enhanced the upward motion and then the TC got stronger.
Zooming in on surface chemical composition of soil microaggregates – Is there an effect of plants (Festuca)?
Authors: Woche Susanne K , Dultz Stefan , Mikutta Robert , Kaiser Klaus , Guggenberger Georg
Published: March 2021

Formation of soil microaggregates (SMA) is a surface-driven process and depends on mineral cementing and organic gluing agents. Yet, the role of plants in soil microaggregation by input of fresh organic matter remains little understood. In a mesocosm experiment silty Luvisol topsoil (<250 µm; original soil material) was incubated in absence (bare soil) and presence of plants (Festuca) and water-stable free and occluded SMA were isolated after 4, 12, and 30 weeks and investigated for the surface chemical composition by X-ray photoelectron spectroscopy (XPS) and for wetting properties by contact angle determination.

Compared to the original soil, the surfaces of both free and occluded SMA tended to smaller O and larger C contents, thus a smaller O/C ratio, along with a slight increase in initial contact angle from about 10° (original soil) to about 20° (SMA). The O/C ratio decreased slightly further from 4 to 12 weeks, especially for bare soil without plants. Slightly greater C contents were detected for occluded than for free SMA, probably hinting at higher retention of organic matter on surfaces of microaggregates entrained in larger soil structures. For bare soil, a slightly greater N content was observed for free SMA while in the presence of Festuca free and occluded SMA had same N contents.

Regardless of the presence of Festuca, C speciation indicated a lower proportion (in % of total C) of C=O/O-C-O and a higher proportion of C - C/C -  H species for occluded than for free SMA, probably indicating less altered organic matter at the surfaces of occluded SMA. While the proportion of C=O/O-C-O species slightly decreased, that of C- C/C-H species slightly increased towards the end of the incubation. This may hint at some preferences in microbial respiration with respect to C compounds and formation of microbial metabolites. From N speciation a higher ratio between protonated and non-protonated organic N species (Np/Nnp) was indicated for Festuca than for bare soil after 4 and for 30 weeks of incubation, i.e., the presence of plants seems to impact N compounds present. The Np/Nnp ratio tended to decrease after 30 weeks compared to 4 weeks for both treatments, hinting on changes in N species present.

In summary, aside some effect on N species present, results indicate rather incubation and SMA origin (free, occluded) than the presence of plants (Festuca) to impact surface chemical composition of the tested SMA. This suggests no defined contribution of plants and their products to formation of 250-53 µm-sized SMA.
Clustering coupled biochemical-physical model results formalizes regional provinces in a coastal region
Authors: Allen Susan , Jarnikova Tereza , Olson Elise , Ianson Debby
Published: March 2021

Coastal regions by their very nature are dynamically diverse.  Within one geographical region there are often multiple areas dominated by substantially different dynamics that shape not only the physical characteristics but also the ecosystem.  The Salish Sea, in the northeast Pacific, is an excellent example with strongly tidally mixed regions, freshwater-dominated regions, and regions directly influenced by the open ocean.  These regions are generally well known and multiple disciplines refer to them with various boundaries and under various names.  Here we use unsupervised clustering on numerical model results to formalize these regional provinces.  The model is SalishSeaCast,  a three-dimensional real-time coupled bio-chem-physical model based on the NEMO framework.  We find that the regions clustered on ecosystem variables (phytoplankton biomass) spatially coincide with those clustered on physical variables, particularly the stratification as diagnosed by the halocline depth.  The clusters are robust across years with interannual variability manifesting mostly in changes in the size of the clusters.  As the clusters are dynamically distinct, they provide a natural framework on which to evaluate the model against observations.  We find that the model accurately simulates each of the major clusters.  The spatial and temporal resolution of the model can then characterize these different clusters more systematically than the observations, revealing biases associated with sparse sampling in the observations. Two examples will be given, one addressing a long-standing issue of the productivity gradient in the stratified main basin, the Strait of Georgia, and another concerning the seasonal cycle of productivity in the ocean-influenced Juan de Fuca Strait.
Winter Arctic sea ice freeboard, snow depth and thickness variability from ICESat-2 and NESOSIM
Authors: Petty Alek , Keeney Nicole , Cabaj Alex , Kushner Paul , Kurtz Nathan , Bagnardi Marco , Kwok Ron
Published: March 2021

National Aeronautics and Space Administration's (NASA's) Ice, Cloud, and land Elevation Satellite‐ 2 (ICESat‐2) mission was launched in September 2018 and is now providing routine, very high‐resolution estimates of surface height/type (the ATL07 product) and freeboard (the ATL10 product) across the Arctic and Southern Oceans. In recent work we used snow depth and density estimates from the NASA Eulerian Snow on Sea Ice Model (NESOSIM) together with ATL10 freeboard data to estimate sea ice thickness across the entire Arctic Ocean. Here we provide an overview of updates made to both the underlying ATL10 freeboard product and the NESOSIM model, and the subsequent impacts on our estimates of sea ice thickness including updated comparisons to the original ICESat mission and ESA’s CryoSat-2. Finally we compare our Arctic ice thickness estimates from the 2018-2019 and 2019-2020 winters and discuss possible causes of these differences based on an analysis of atmospheric data (ERA5), ice drift (NSIDC) and ice type (OSI SAF).
3D shear velocity structure of the northwestern South America-Caribbean Subduction Zone from ambient noise and ballistic Rayleigh wave tomography
Authors: Miao Wenpei , Cornthwaite John , Levander Alan , Niu Fenglin , Schmitz Michael , Prieto German , Dionicio Viviana
Published: March 2021

The Caribbean plate (CAR) collided with and initiated subduction beneath northwestern South America (SA) at about 60-55 Ma. Since the onset of subduction, it has formed the Lara nappes and subsequently the Laramide-style uplifts of the Merida Andes, Sierra de la Perija and Santa Marta ranges, with maximum elevations > 5km. The triangular Maracaibo block, bounded by the Santa Marta-Bucaramanga, Bocono and Oca-Ancon Faults, is currently escaping to the north relative to SA over both the subducting and nonsubducting elements of the CAR plate.

Although many petroleum related seismic studies have been done in this area, the details of the subduction geometry of the CAR plate beneath the Maracaibo block remain unclear. The few deeper seismic investigations are either very large scale, very local, or only peripheral to this area. Previous geodetic studies have suggested that this region has potential for a great (M~8+) earthquake (Bilham and Mencin, 2013). To investigate this complex region we fielded a 65 element broadband seismic array to complement the 48 existing stations of the Colombian and Venezuelan national seismic networks. The array is collectively referred to as the CARMArray.

In this study, we jointly inverted ambient noise Rayleigh wave Z/H ratios, phase velocities in the 8-30s band and ballistic Rayleigh wave phase velocities in 30-80s band to construct a 3D S-wave velocity model in the area from 75o-65o west and 5o-12o north. Rayleigh wave Z/H ratios are sensitive to the shallow sedimentary structure, while the phase velocity data have good resolution of the crust and upper mantle. The Vs model shows strong low-velocity anomalies beneath the Barinas-Apure and Maracaibo Basins, and the Paraguana Peninsula that are well correlated with surface geology. Sediment thickness beneath the Maracaibo basin reaches up to ~9 km depth, consistent with previous studies (Kellogg & Bonini, 1982). Crustal thickness beneath the Santa Marta uplift is 27-30 km, shallow for its nearly 4km elevation. From the trench to the southeast, Moho depth increases from 25-30 km near the coast to 40-45 km beneath the Maracaibo Basin, with the thickest crust, ~50 km, lying under the Merida Andes beneath the Bocono Fault. Crustal thickness decreases under the Venezeulan interior to ~45 km. From 50km to 150km depth, the CAR plate shows ~2% high Vs anomalies beneath the Santa Marta uplift and the Serrania de Perija range. Our slab image matches local slab seismicity very well (Cornthwaite et al., EGU 2021 GD7.1), and is consistent with and complements images from teleseismic P-wave tomography (Cornthwaite et al, 2021, submitted).
Dust-dominated coarse particles as a medium for rapid secondary organic and inorganic aerosol formation in highly polluted air
Authors: Kuang Ye , Xu Wanyun , Liang Linlin , He Yao , Cheng Hongbin , Bian Yuxuan , Tao Jiangchuan , Zhang Gen , Zhao Pusheng , Ma Nan , Zhao Huarong , Zhou Guangsheng , Su Hang , Cheng Yafang , Xu Xiaobin , Shao Min , Sun Yele
Published: March 2021

Secondary aerosol (SA) frequently drives severe haze formation on the North China Plain. However, previous studies mostly focused on submicron SA formation, thus our understanding of SA formation on supermicron particles remains poor. In this study, PM2.5 chemical composition and PM10 number size distribution measurements revealed that the SA formation occurred in very distinct size ranges. In particular, SA formation on dust-dominated supermicron particles was surprisingly high and increased with relative humidity (RH). SA formed on supermicron aerosols reached comparable levels with that on submicron particles during evolutionary stages of haze episodes. These results suggested that dust particles served as a medium for rapid secondary organic and inorganic aerosol formation under favorable photochemical and RH conditions in a highly polluted environment. Further analysis indicated that SA formation pathways differed among distinct size ranges. Overall, our study highlights the importance of dust in SA formation during non-dust storm periods and the urgent need to perform size-resolved aerosol chemical and physical property measurements in future SA formation investigations that are extended to the coarse mode because the large amount of SA formed thereon might have significant impacts on ice nucleation, radiative forcing, and human health.
The first soil moisture reconstruction in the Mediterranean Chilean Andes region developed by tree rings and satellite observations to inform climate change impacts in South America
Authors: González-Reyes Álvaro , Venegas-González Alejandro , Muñoz Ariel , Schneider Isadora
Published: March 2021

Soil moisture (SM) is a key variable in the earth surface dynamics; however, long-term in situ measurements at the global scale are scarce. In the Mediterranean Chilean Andes (MA; 30°-37°S), Sclerophyllous Forest tree species such as Belloto del Norte (BN; Beilschmiedia miersii) can grow for more than two centuries in very scarce humid lowland geographical zones. At the present work, we assess the linkages between two BN tree-ring chronologies (BML and AGU sites; 70 cores) and daily high-resolution satellite-based surface soil moisture product v201812.0 from ESA and to reconstruct past SM variations in the MA region. Our findings exhibit strong relationships between tree-growth from BML and AGU sites and the SM from 32°-34°S and 71°-73°W spatial domain, especially from February to September. We found significant r Pearson correlations of 0.85 and 0.68 during 1983-2014 (P-value < 0.001), respectively. Based on these results, we reconstructed the SM between 1800 - 2014 period using multiple linear regression. Our model retains 71.4% of the total variance and exhibits an unprecedented SM reduction since 2006 in the context of the past two centuries. This work constitutes the first reconstruction of surface soil moisture variability derived from remote sensing carried out in Chile, and can provide new information to understand current environmental changes related to the severe mega-drought period experienced in  Chile since 2010, which has provoked water conflicts, the Sclerophyllous Forest decline and browning, and the intensification of climate extreme events such as heatwaves and wildfires in the MA. 

Acknowledgments

Álvaro González-Reyes wish to thank: ANID+PAI+CONVOCATORIA NACIONAL SUBVENCIÓN A INSTALACIÓN EN LA ACADEMIA CONVOCATORIA AÑO 2019 + PAI77190101. Ariel Muñoz and Isadora Schneider thanks to the FONDECYT 1201714 and the Center for Climate and Resilience Research (CR)2, FONDAP 15110009.   
Depositional signatures of historical flood and human landscape disturbances in lakes of the northeastern U.S. 
Authors: Cook Timothy , Snyder Noah
Published: March 2021

Sedimentary archives in lakes and ponds are widely used to reconstruct past climatic and environmental conditions, as well as to quantify the environmental impacts of human activity. In this study, we summarize the characteristics of sedimentary deposits associated with different types of disturbances including floods, landslides, timber harvest, and conversion of forested land to agricultural use. We evaluated sediment cores from a network of lakes across the northeastern U.S. The watersheds span a range of topographic and surficial geologic characteristics, and have land-use histories with differing types, timing, intensity, and duration of anthropogenic disturbance. Cores were analyzed to identify distinct event deposits and changes in clastic sediment input indicative of landscape disturbances. While most records span the past millennium, we focus specifically on the period of record that overlaps with historical and instrumental records of events that can be linked to specific sedimentary deposits. Neither hydroclimatic nor human land-use signals are ubiquitous across all watersheds. The identification of distinct flood deposits was limited to higher relief, mountainous watersheds with abundant glacial-age sediment. Distal flood deposits are typically thin (mm to cm scale) and characterized by sharp contacts between dominant gyttja and fine-grained clastic flood layers. Hydrologic disturbances associated with landslide activation (such as occurred during tropical storm Irene in 2011) result in similarly sharp basal contacts between gyttja and clastic sediment. However, these deposits are commonly thicker (10s of cm) and characterized by compositional grading from more clastic to more organic rich sediment, and have complex patterns of textural variability. These signatures reflect a multi-year duration of elevated sediment delivery as the landscape gradually stabilizes and vegetation returns. In contrast, human land cover alteration typically manifests in sediments as a gradual and often prolonged increase in clastic content. Thick (up to 10s of cm), often sandy, texturally graded clastic deposits are distinct from those formed by both hydrologic and human disturbances, and interpreted as a consequence of subaqueous mass movements.
Towards real-time global assessment of post-fire debris flow hazards with remotely sensed data
Authors: Orland Elijah , Kirschbaum Dalia , Stanley Thomas
Published: March 2021

As the risk of wildfires increases worldwide, burned steeplands are vulnerable to the secondary hazard of widespread sediment mobilization through debris flows. Following an initial burn, sediment and soil previously restrained by vegetation are no longer consolidated, allowing for easy mobilization into channels and along steep hillslopes through runoff.  Sufficiently powerful rainfall incorporates entrained material into turbulent flows and serves as the primary trigger for debris flow initiation. There is thus an ongoing need to establish the relationship between rainfall and debris flow initiation based on a variety of spatiotemporal preconditions. Previous work establishes regional and local thresholds to constrain the effect of rainfall in recently burned areas, but no empirical or numerical solution has worldwide application. Building from regionally-based efforts in the U.S., this work considers how remote sensing data can be applied to better approximate the post-fire debris flow hazards worldwide using freely available global datasets and software. Our work assesses the utility of remote sensing resources for analyzing burn characteristics, topography, rainfall intensity/duration, and, thus, debris flow initiation. Early results show that global observations are sufficient to delineate background rainfall rates from storms likely to cause debris flows across a variety of burn severity and topographic conditions. However, the dearth of publicly-available post-fire debris flow inventories globally limit the ability to test how the model framework performs within different climatologic and morphologic areas. This work will present preliminary analysis over the Western United States and demonstrate the feasibility of a global, near-real time model to provide situational awareness of potential hazards within recently burned areas worldwide. Future work will also consider how global or regional precipitation forecasts may increase the lead time for improved early warning of these hazards.
Hydro-Economics Tradeoff Surfaces to Guide Unit Commitment in Production Cost Models
Authors: Ploussard Quentin , Voisin Nathalie , Veselka Thomas , Oikonomou Konstantinos
Published: March 2021

This paper aims to assess the discrepancy in hydropower representation between conventional PCMs and hydro scheduling tools and propose a new method to account for hydrological and environmental aspects in PCMs. To achieve this, three scenarios are simulated. The first scenario simulates hydropower operations using a conventional PCM. The second scenario uses an iterative method to integrate into a PCM the hydropower operations modeled by a hydro scheduling tool. The third scenario explores a hybrid alternative in which hydropower operations are simulated based on dynamic hydropower parameters calculated from detailed environmental constraints. These dynamic hydropower parameters are calculated via “surfaces”, or bivariate functions, generated in advance by the hydro scheduling tool used in scenario 2 under numerous hydrological conditions.
Hydraulic Characteristics of Concentrated Flow Relative to Angle between Rock Strata and Slope in the Karst Trough Valley Area
Authors: Zeng Cheng , Zeng RongChang , He BingHui
Published: March 2021

Abstract: Outcrops of rock strata in the Karst Trough Valley Area often form angles with slopes, thus making micro landforms complicated and altering significantly paths of concentrated flows, and consequently bringing about great changes in characteristics of the flows. So, it’s important to study hydraulic characteristics of the concentrated flows relative to angle between rock strata and slope. To that end, a flume experiment, designed to have combinations of three slope gradients (10°,15° and 20°), three flow rates (5, 7.5 and 10 L·min-1) and six angles between the rock strata and slope (30°, 60°, 90°, 120°, 150° and 180° (0°)), was carried out. Results show that hydraulic characteristics of a concentrated flow varied significantly with the angle between the rock stratum and slope. Reynolds number (Re) of the concentrated flow changed with duration of the scouring in a complicated trend, but exhibited a significant trend of increasing with rising flow rate, and an insignificant one of changing with slope gradient. And it varied in the range of 517~3343 in the experiment. Darcy-Weisbach friction coefficient (f) of the concentrated flow increased with rising slope gradient and with scouring going on, but decreased with rising flow rate. And it varied in the range of 0.62~5.70 in the experiment. The relationship of Re with angles between rock strata and the slope was not significant, but that of f varied with combinations of slope gradient and flow rate. The coupling relationship between f and Re was influenced significantly by the angle between the rock stratum and the slope. It could be better described with a logarithmic equation when the angle between the rock stratum and the slope was narrower than 90°, and with a power function equation when the angle between the rock stratum and the slope was wider than or equal to 90°. In the experiment, when Re<1791, the relationship between f and Re was not apparent, but when Re>1791, it was significantly positive. To sum up, f and Re and their relationship vary with the angle between the rock stratum and the slope. The findings in this experiment may provide strong data support for establishing soil erosion prediction models in the Karst Trough Valley Area.
Interpretability in Convolutional Neural Networks for Building Damage Classification in Satellite Imagery
Authors: Chen Thomas
Published: March 2021

Natural disasters ravage the world's cities, valleys, and shores on a monthly basis. Having precise and efficient mechanisms for assessing infrastructure damage is essential to channel resources and minimize the loss of life. Using a dataset that includes labeled pre- and post- disaster satellite imagery, the xBD dataset, we train multiple convolutional neural networks to assess building damage on a per-building basis. In order to investigate how to best classify building damage, we present a highly interpretable deep-learning methodology that seeks to explicitly convey the most useful information required to train an accurate classification model. We also delve into which loss functions best optimize these models. Our findings include that ordinal-cross entropy loss is the most optimal loss function to use and that including the type of disaster that caused the damage in combination with a pre- and post-disaster image best predicts the level of damage caused. We also make progress in the realm of qualitative representations of which parts of the images that the model is using to predict damage levels, through gradient class-activation maps. Our research seeks to computationally contribute to aiding in this ongoing and growing humanitarian crisis, heightened by climate change. Specifically, it advances the study of more interpretable machine learning models, which were lacking in previous literature and are important for the understanding of not only research scientists but also operators of such technologies in underserved regions.
Station Correction of P-Alert Network to Improve Magnitude Estimation for Earthquake Early Warning
Authors: Wu Yu-Ting , Wu Yih-Min
Published: March 2021

Magnitude estimation for earthquake early warning has been shown that it can be achieved by utilizing the relationship among the first three seconds P-wave amplitude, hypocentral distance and magnitude. However, the regression models in previous studies about P-Alert didn't include station correction factors, which may cause non-negligible effects. Thus, to improve the precision of magnitude estimation, we take station corrections into consideration when building the regression model. For the reason that station corrections are the unobserved latent variables of the model, we adopt the iteration regression method, which is based on the expectation-maximization algorithm, to determine them. By using this method, we are able to approach the values of both the station corrections and the coefficients of the regression model after several iterations. Our preliminary results show that after utilizing the iteration regression method, the standard deviation reduces from 0.30 to 0.26, and the station corrections we get range from -0.70 to 0.66.
Wormhole Growth in Dissolving Limestones: Insights from 4D Tomography
Authors: Szymczak Piotr , Cooper Max P , Magni Silvana , Sharma Rishabh P , Blach Tomasz P , Radlinski Andrzej P , Dohnalik Marek , Tengattini Alessandro
Published: March 2021

Dissolution of porous media introduces a positive feedback between fluid transport and chemical reactions at mineral surfaces leading to the formation of pronounced wormhole-like channels. While the impact of flow rate and reaction rate on the shapes of the wormholes is now well understood, much less is known about the dynamics of their propagation. In this study we capture the evolution of wormholes and their effects on flow patterns by in-situ X-ray microCT imaging of dissolving limestone cores. 4D tomography allows us in particular to correlate the permeability changes in a dissolving core with the advancement of the tip position of the wormhole. Surprisingly, we find that the relation between the two is highly nonlinear, with extensive periods of relatively fast growth of the wormhole which is nevertheless not reflected in any significant change in the overall permeability.  We hypothesize that this is caused by the presence of highly cemented regions in the core which act as permeability barriers for the flow. The presence of such regions is confirmed by a detailed analysis of the pore geometry based on the tomographic data. The results demonstrate that the analysis of the wormhole dynamics in 4d tomography can be used to probe the internal structure of the rock. 
Statistical analysis of tidal effect on non-volcanic earthquake swarm activity in Wakayama Prefecture, southwest Japan
Authors: Machida Kazuki , Nagahama Hiroyuki , Muto Jun
Published: March 2021

Earthquakes occur when the fault stress accumulates to the critical level. External forces such as tidal forces may contributes to the triggering of earthquakes reaching the critical state. For example, in the case of 2011 Tohoku Earthquake, it is reported that there is a correlation between tidal forces and the earthquakes prior to the mainshock. Earthquakes with smaller magnitude are also affected by tidal forces and expected to show correlation with tidal forces.

Tidal triggering of non-volcanic seismic swarm has not been well documented. So, we choose the Wakayama Prefecture as a targeting region. The cause of the earthquakes occurring in the region is considered to be the presence of the water below the seismogenic depth. The swarm activity continues from 1980s. We analyzed the shallow earthquakes in the northern part of Wakayama Prefecture from 1998 to 2016. We used statistical method called Schuster test to analyze correlation between earthquakes and tidal stress.

The result of the analysis shows that the earthquakes have a correlation with tidal forces which have the periodicity near the half of the lunar day and the amplitude of the seismicity-rate variation is about 16% of the average earthquake frequency. Correlation between the earthquakes and tidal forces is stronger at the periods when larger number of earthquakes occur. From tidal stress calculation, it is found that both solid tide and oceanic tide are important at this region. This study confirms that most of the earthquakes larger than Mw 4 in the region occur in the rising period of tidal normal stress or just after the maximum of tidal normal stress. Therefore, tidal observation gives information about the criticality of rocks and temporal heterogeneity of the earthquake occurrence.
Restriction threshold of vapor pressure deficit for light use efficiency varied with soil water content
Authors: Gao Dexin , Wang Shuai , Li Zidong , Wei Fangli , Chen Peng , Fu Bojie , Song Shuang , Wang Yaping
Published: March 2021

Understanding the constraints on light-use efficiency (LUE) created by high evaporative water demand (vapor-pressure deficit; VPD) and restricted water supply (soil moisture content; SMC) is crucial for understanding and simulating vegetation productivity, particularly in arid and semi-arid regions. However, the relative impacts of VPD and SMC on photosynthesis are unclear, as we lack a mechanistic understanding of them and their interactions. In this study, we quantified the relative roles of VPD and SMC in limiting LUE and analyzed the interactions among VPD, SMC, and LUE in China’s Heihe River Basin using data from CO2 and water flux stations and weather stations along a climatic gradient. We found a threshold for VPD’s restriction of LUE; above the threshold, LUE decreased at only 3.6% to 23.1% of the rate below the threshold. As SMC decreased, however, the VPD threshold increased, and the reduction of LUE caused by VPD decreased significantly, which is more than half lower than that in moister regions. Therefore, both VPD and SMC played essential roles in LUE limitation and the resulting reduction of photosynthesis caused by water stress. A threshold also existed for heat flux and the correlation between SMC and LUE; the strength of the correlation first decreased and then increased with increasing VPD. Our results clarified the relative impacts of VPD and SMC on photosynthesis, and can improve simulation and prediction of plant productivity.
Quantifying the impact of climate change on tropical cyclone rainfall using a model hierarchy 
Authors: Reed Kevin , Stansfield Alyssa , Bower Erica
Published: March 2021

Changes in extreme events, such as the recent devastating tropical cyclones (TC), are a visible way in which climate change can directly impact society and coastal communities. This work presents the results of a model hierarchy within the Community Earth System Model (CESM), that spans idealized radiative convective equilibrium to realistic decadal projections of future climate change configurations, to explore how TC rainfall characteristics change with surface warming. The Community Atmosphere Model (CAM) component of CESM is forced with prescribed sea-surface temperatures (SSTs) and greenhouse gas concentrations for idealized and realistic representations of past, present, and future climates using global and variable-resolution setups with high-resolution horizontal grid spacing equal to 28 km. An analysis framework that allows for the extraction of TC-related rainfall throughout the full storm lifecycle is utilized. This analysis includes the evaluation of conventional (AMIP-style) decadal simulations typical of climate models, short 7-day ensemble hindcasts of recent devastating events, and reduced complexity simulations of idealized states of the climate system. Through this hierarchical modeling approach the impact of climate change on the characteristics (rainfall, structure, intensity, etc.) of TCs can be quantified This work is part of a growing effort in the scientific community to quantify the impact of climate change on recent and future extreme weather events.
Vertical slab tearing controlled by the rheology of subducting oceanic plates
Authors: Chen Yaguang , Chen Hanlin , Gerya Taras , Liu Mingqi
Published: March 2021

Vertical tearing of subducting oceanic slabs plays an important role in the subduction dynamic worldwide, accommodating slabs motion and segmentation in subduction zones. In previous studies, several models have been proposed for the origin of vertical slab tearing – they were related to variations in the slab age, rollback rate, buoyancy, moving direction, etc. However, the physical mechanism of vertical slab tearing remains elusive. Here, we propose a new model that stable vertical tearing of subducting oceanic slabs can be generated by inversion of transform margins and controlled by the strain-weakening rheology of subducting oceanic plates that facilitate out of plane (mode-III) shear deformation inside subducting slabs. Through 3D thermo-mechanical numerical modeling, we systematically investigate the effects of transform margins length and the rheology of subducting oceanic plates on the vertical slab tearing. Numerical results show that (1) interaction between two neighboring subducting slabs decreases as the transform margins length and the resulting trench offset increase. Once the offset reaches the critical offset, sustained vertical slab tearing occurs spontaneously. (2) Strain weakening parameters are crucial in the lithospheric deformation. An intense strain weakening, with a strong and rapid lowering of internal friction coefficient, greatly facilitates the initial slabs tear and makes it sustained. (3) Slab age is also an important factor in vertical slab tearing. A longer critical offset is required for the older oceanic lithosphere. (4) The vertical tear and resulting slab segmentation can operate as a self-sustained dynamical process (i.e., can be defined as dynamical instability of oblique subduction that gives preference to segmented slabs). Once a vertical tear is formed, it can propagate steadily for a long time.
The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations
Authors: Nowrouzi Niloufar , Kistler Lynn , Lund Eric , Zhao Kai
Published: March 2021

Sawtooth events are repeated injections of energetic particles at geosynchronous orbit. Although studies have shown that 94% of sawtooth events occur during  magnetic storm times, the main factor that causes a sawtooth event is unknown. Simulations have suggested that heavy ions like O+ may play a role in driving the sawtooth mode by increasing the magnetotail pressure and causing the magnetic tail to stretch. O+ ions located in the nightside auroral region have a direct access to the near-earth plasma-sheet. O+ in the dayside cusp can reach to the midtail plasma-sheet when the convection velocity is sufficiently strong. Whether the dayside or nightside source is more important is not known.

We show results of a statistical study of the variation of the O+ and H+ outflow flux during sawtooth events for SIR and ICME sawtooth events. We perform a superposed epoch analysis of the ion outflow using the TEAMS (Time-of-Flight Energy Angle Mass Spectrograph) instrument on the FAST spacecraft. TEAMS measures the ion composition over the energy range of 1 eV e-1 to 12 keV e-1.  We have done major corrections and calibrations (producing 3D data set, anode calibration, mass classification, removing ram effect and incorporating dead time corrections) on TEAMS data and produced a data set for four data species (H+, O+, and He+). From 1996 to 2007, we have data for 133 orbits of CME-driven and for 103 orbits of SIR-driven sawtooth events with an altitude above 1500 km. We found that:

the averaged O+ outflow flux is more intense in the cusp dayside than in the nightside, before and after onset time.

Before onset, an intense averaged outflow flux in the dawnside of CME events is seen. This outflow decreases after onset time.

In both CME-driven and SIR-driven, the averaged O+ outflow increases after onset time, in the nightside, cusp dayside. This increase is greater on the nightside than in the cusp.

We will develop this study by performing a similar statistical study for H+ outflow and finally will compare the H+ result with the O+ result.