bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotropic Scaling Features Measured Locally in the Solar Wind Turbulence with Stationary Background Field
Authors: Wu Honghong , Tu Chuanyi , Wang Xin , He Jiansen , Yang Liping , Wang Linghua
Published: March 2020

The scaling anisotropy is crucial to interpret the nonlinear interactions in solar wind turbulence. Previous observations provide diverse results and the structure functions analyses are also reported to be an approach to investigate the scaling anisotropy based on a local magnetic field. However, the determination of the sampling angle with respect to the local background magnetic field implicitly assumes that the observed time series are time stationary. If this assumed time-stationarity is compatible with the measurements has not been investigated. Here we utilize the second-order structure function method to study the scaling anisotropy with a time-stationary background field. We analyze 88 fast solar wind intervals each with time durations >=2 days measured by Wind spacecraft in the period 2005-2018. We calculate the local magnetic field as the average of the time series B(t') whose time-stationarity are fulfilled by our criterion φ<10o (φ is the angle between the two averaged magnetic field after cutting B(t') into two halves). We find for the first time the isotropic scaling feature of the magnetic-trace structure functions with scaling indices -0.63±0.08 and 0.70±0.04 respectively in the local parallel and perpendicular directions. The scaling for the velocity-trace structure functions is also isotropic and the indices are -0.47±0.10  and 0.51±0.09. 
The Next Generation Drought Index Project
Authors: Osgood Daniel , Enenkel Markus ,   Daniel E Osgood
Published: March 2020

There is ample evidence about the added-value of anticipatory financing mechanism to mitigate the impact of extreme droughts on the livelihoods of vulnerable communities. Various projects have tried to optimize parametric insurance via different methods, resulting in useful lessons learnt for both macro- and micro-level insurance. In parallel, novel satellite-derived sources of information, such as soil moisture or evaporative stress, have become available to monitor key variables of the hydrological cycle and strengthen the drought narrative via cross-validation.  The Next Generation Drought Index project was funded by the World Bank to develop a generic framework and related technical toolbox that allows decision-makers to understand every step of index design, calibration and validation. An interactive dashboard is linked directly to different data sources, the outputs of financial risk models and socioeconomic information to link climate hazard and impact information. Collaboration partners range from African Risk Capacity to the United Nations World Food Programme, the START Network, the World Bank’s Global Index Insurance Facility and the European Space Agency. The overall goal is to reduce basis risk without creating an analytical black box as well as to identify and use ‘low hanging fruits’, such as the detection of early season moisture deficits via remote sensing. The finding from Senegal suggest that the effectiveness of insurance might be improved through client centered design through participatory/crowdsourced processes, a suite of advanced satellite data and models, available government/institutional data and  structured decision tree processes based on key performance indicators.
Ice-wedge polygons distribution, morphometry and state in the Tombstone Territorial Park, Central Yukon, Canada
Authors: Frappier Roxanne , Lacelle Denis
Published: March 2020

Ice wedge (IW) polygons form through thermal contraction induced by winter cooling of ice-rich permafrost which results in the formation of cracks. Hoar frost develops in the cracks in winter and meltwater infills the cracks during spring and freezes. As the cracking and infilling occurs repeatedly, IWs grow, leading to characteristic surface morphology with depressions or troughs aligned on the axis of the IW and raised rims or ridges on either side. Surface expression of IW is either characterized as low-centered polygons or high-centered polygons, the former being associated with the first stages of IW development, and the latter with IW degradation. Because IWs represent important excess ice close to the surface, considerable local subsidence and related effects on landscape parameters, such as vegetation and moisture, are likely to occur upon degradation.

IW polygons distribution, morphometry and state were characterized in the Tombstone Territorial Park (Central Yukon, Canada) using semi-automated remote sensing techniques, field observations and laboratory analyses. The data is used to define determining landscape factors for IW polygons occurrence, to characterise the stages of the IWs development and/or degradation and to estimate the volume of buried ice in the region. Results show that elevation, slope and material are important elements defining IW polygons distribution. The relationship between landscape factors and stages of development is not as clear, and, despite climate changes being homogenous in the area, IW development and degradation is very heterogenous, as shown by the differing moisture, greenness and brightness signals across the polygonal terrain.
Optimization of an Integrated Water Resources Model in tropical regions
Authors: Donado Leonardo David , Arenas-Bautista María Cristina
Published: March 2020

Water resources management must be in all cases, effective, efficient and sustainable, especially when considering the effects of climate change and variability effects. The challenge tackled in this research was to build a hydro-economic optimization model, which can be used as a decision-making tool for water assignment between several users in a tropical region. The model has been developed by integrating hydrological aspects (surface water and groundwater) in an economical optimization framework for water allocation and water quality management.

We study a basin of 17 000 km2 located in the Colombian Middle Magdalena Valley (MMV), a central area with important economic activities, as oil and gas exploration and production (O&G), agriculture and livestock.

A regional optimization model that integrates multiple water supplies and demands were designed.  The main purpose of the model is to maximize the value of water consumption. Consequently, the hydro-economic model was solved through a lineal optimization process, that links all available water resources and all water demands under the limitations of: (i) demand rising, (ii) water quality variance and (ii) offer decrease.

The system considers the monthly water demand from each user and a penalty for no satisfy it. For hydro-economic analysis, the model contemplates four main study scenarios: (i) current mean condition (ESC1), (ii) at thirty years (ESC2), (iii) at fifty years (ESC3) and, (iv) at hundred years (ESC4). These scenarios show fluctuation in water demand, and water supply based on the population increase. The results show significant differences between the user's allocation regimes. This has been identified between domestic and agricultural sectors, but not between commercial activities. According to the later, it is important to include variable rates for each sector according to its productivity, in the general analysis.

The defined objective function maximizes the profit in the MMV basin during a planning period of a year.  It is important to highlight that the whole system was optimized under an equitable distribution in allocation and costs, and thus, the resulting profits would improve results to satisfy all economic sectors.
Well location optimization of Zama reservoir using top down reservoir modeling(TDRM)
Authors: Lee Taehun , Lee Kyungbook , Lee Hyunsuk , Lee Wonsuk
Published: March 2020

Artificial intelligence is applied in various fields of human life and is being actively studied and applied in the oil fields. Especially, the digital oil field, which has recently been spotlighted, is required to simulate the reservoir using artificial intelligence. However, there is almost little research to date. Therefore, in this study, we applied TDRM using artificial intelligence technology to Zama field located on the land of Canada. The required static and dynamic data were obtained from Accumap, a Canadian well information S/W. As a result, the reservoir model was constructed successfully and the well location optimization could be performed in a short time using TDRM.
Mediterranean Marine heatwaves: On the comparison of the physical drivers behind the 2003 and 2015 events
Authors: Darmaraki Sofia , Somot Samuel , Waldman Robin , Sevault Florence , Nabat Pierre , Oliver Eric
Published: March 2020

Over the last decade, an intensification of extreme warm temperature events, termed as marine heatwaves (MHWs), has been reported in the Mediterranean Sea, itself a “Hot Spot” region for climate change. In the summer of 2003, a major MHW occurred in the Mediterranean with abnormal surface temperature anomalies of 2-3 Cº persisting for over a month. In 2015, an undocumented but more intense summer MHW affected almost the entire Mediterranean Sea with regional temperatures anomalies reaching 4-5 Cº. Here, we apply a MHW detection algorithm for long-lasting and large-scale summer events, on the hindcast output of a fully-coupled regional climate model (RCSM). We first examine the spatial variability and temporal evolution of both the 2003 and 2015 events. Then a basin-scale analysis of the mixed layer heat budget during each MHW is performed. The ocean and atmospheric components’ contribution is investigated separately during the onset, peak, and decay phases of both events, in order to disentangle the dominant physical processes behind each event. On the large-scale, our results indicate a key role of the wind forcing and the air-sea heat fluxes, while advection processes become more important at local scales. This study provides a comparison of the underlying mechanisms behind the two most intense MHW detected in the Mediterranean Sea during the last decade, constituting key information for the marine ecosystems of the region.
Air-sea Interface Exchanges in Rapidly Intensifying Tropical Cyclones
Authors: Soloviev Alexander , Vanderplow Breanna , Lukas Roger
Published: March 2020

Rapid intensification of tropical cyclones is a challenge for forecasters. In 2017, Hurricane Maria intensified to a Category 5 storm within 24 hours and devastated Puerto Rico. The official forecast and all computer models were unable to predict it. Hurricane Dorian had been predicted as a tropical storm; unexpectedly, it intensified into a Category 5 storm and destroyed the Bahamas. Soloviev et al. (2017) suggested that under the assumption of constant enthalpy exchange coefficient, rapid cyclone intensification and decay can be related to the drag coefficient dependence on wind speed including an “aerodynamic drag well” around 60 m/s. This concept is in general terms consistent with Emanuel’s (1988) theory of maximum potential intensity of a tropical cyclone and its extension by Lee et al. (2019). The influence of sea spray is still a significant uncertainty. In order to study the effect of spray on dynamics of tropical cyclones, we have implemented a Volume of Fluid to Discrete-Phase Model (VOF to DPM). This model re-meshes the areas with increased gradients or curvature, which are suspicious for the interface instability. The generated water particles that satisfy the condition of asphericity are converted into Lagrangian particles. The size distribution of spray measured in air-sea interaction facilities is used for the model verification. Due to dynamic remeshing, VOF to DPM resolves spray particle radius from ten micrometers to a few millimeters, which correspond to spume. Results of the numerical simulation show a dramatic increase of spume generation under major tropical cyclones. Though sub-micrometer and micrometer scale spray particles are not resolved in this simulation, they are likely less significant in the momentum exchange at the air-sea interface than spume. These results are expected to contribute to the parameterization and proper treatment of spray in forecasting models, including cases of rapid intensification and rapid decline of tropical cyclones.
References:
Emanuel, K. A. (1988). The maximum intensity of hurricanes. JAS 45, 1143–1155.
Soloviev, A. V., Lukas, R., Donelan, M.A., Haus, B. K., Ginis, I. (2017). Is the state of the air-sea interface a factor in rapid intensification and rapid decline of tropical cyclones? JGR - Oceans 122, 10174-10183.
Lee, W., Kim, S.‐H., Chu, P.‐S., Moon,I.‐J., and Soloviev, A. V. (2019). An index to better estimate tropical cyclone intensity change in the western North Pacific. GRL 46, 8960-8968.
Analyzing Land Use Impacts on Streamflow Response in a Tropical Watershed: A Hydrometric and Geochemical Approach
Authors: Mathura Nicola , Farrick Kegan
Published: March 2020

Climate change and unsustainable land use practices such as quarrying have the potential to negatively impact the hydrology and water resource availability in catchments. Throughout the Caribbean, hillside quarrying has become a common practice. While these activities remove large sections of the critical zone, very little work has been done on how hillside quarrying impacts storm response and catchment water storage.  The study is particularly important given the expected changes to rainfall patterns in the Caribbean under future climate change. We hypothesised that the removal of the critical zone during quarrying will increase the magnitude of streamflow response to storm events due to its close proximity to the river, while also reducing the overall storage of the watershed. This study utilized a hydrometric and geochemical approach with direct measurements of rainfall and streamflow, and bi-weekly water sample collections for geochemistry and 18O and 2H stable isotopes between the 3.6 km2 Acono (forested) and the adjacent 3.6 km2 Don Juan (quarried) watersheds, located in Trinidad and Tobago. A total of 1207 mm of rainfall occurred, with 87.3% falling from August to November (wet season) and 12.7% from December to March (dry season). The δ 18O in rainfall ranged from -7.7 to 0.3 ‰ across both seasons with an average δ18O of -3.5±1.8‰ during the wet season and 0.1±0.5‰ in the dry season. During the dry season the mean δ 18O of stream water showed a difference between the forested (-2.8±0.3‰) and quarried (-3.1±0.3‰) catchments whereas there was little differences in δ18O in the forested catchment (-3.3±0.3 ‰) and quarried catchment–(-3.2±0.27‰) in the wet season. Our stream δ18O dry season results suggests that different sources of water or anthropogenic influences such as water from settling ponds in the quarry could have impacted the δ18O of the quarried stream as we expected the forested catchment to be more stable. Sample collection at these sites is ongoing and additional parameters such as soil water isotopes and rainfall, soil and stream ion chemistry are expected to improve our understanding of the translation from rainfall to streamflow. This research will allow us to gain a better insight of the current hydrological processes within this catchment and aid in the long term adaptive planning for factors such as climate change and further land use change.

 
A Study on the Effects of the Anthropogenic Heat Fluxes on the Temperature Distribution in an Urban Area
Authors: Mun Da-Som , Kim Jae-Jin
Published: March 2020

In this study, we investigated the effects of the anthropogenic heat caused by the energy usage on the air temperature distributions in an urban area using a CFD model. We calculated the anthropogenic heat fluxes using a top-down method with monthly and hourly allocation coefficients and the total amount of the yearly electrical energy usage of buildings. To construct the buildings and to estimate the anthropogenic heat fluxes in the CFD model for the target area, we used the land use and GIS data. We conducted the CFD simulations for the heatwave period (2018.08.02 ~ 2018.08.08) in a building-congested district around the Seoul ASOS (ASOS 108) to see how the anthropogenic heat fluxes affected the thermal environment in the target area. The target area is mostly composed of commercial and residential areas. The temperature increased near the roads and buildings. At the night time, the temperature increase near the buildings with high anthropogenic heat fluxes was more significant than the daytime. The comparison with the ASOS-observed temperatures showed that the inclusion of the anthropogenic heat fluxes improved the CFD simulations of temperatures.
CFD Simulations of Flows in Step-up Street Canyons
Authors: Park Soo-Jin , Kim Jae-Jin , Pardyjak Eric , Hong Ji-Yoon
Published: March 2020

We analyzed the flow characteristics in strep-up street canyons using a computational fluid dynamics (CFD) model. Simulated results are validated against experimental wind-tunnel results, with the CFD simulations conducted under the same building configurations (Hu/Hd = 0.33, 0.6 and L/S = 1, 2, 3, and 4; Hu, Hd, L, and S respectively indicate the upwind, downwind building heights, the building length and street-canyon width) as those in the wind-tunnel experiments. The CFD model reproduced the in-canyon vortex, recirculation zones above the downwind buildings, and stagnation point position reasonably well. Furthermore, we analyze the flow characteristics in the step-up street canyons based on the numerical results. The in-canyon flows simulated in the shallow (Hu/Hd = 0.33) and deep (Hu/Hd = 0.6) street canyons underwent two stages (development and mature stages) as the building-length ratio increased. In the development stages, one clockwise-rotating vortex was formed in the step-up street canyons and its center was slightly tilted toward the wall of the upwind building. However, in the mature stages, two clockwise-rotating vortices were formed in the upper and lower layers. A clockwise vortex and a counterclockwise vortex were stabilized as the building width ratio increased.
Exploring The Birch Effect In The Subsurface Using Diffusive Soil Probes
Authors: Roscioli Joseph , Shorter Joanne , Krechmer Jordan , Meredith Laura , Gil Loaiza Juliana
Published: March 2020

Soil gases are efficient messengers of the subsurface biogeochemical processes that underlie important nutrient cycles.  Recent advances in subsurface gas sampling techniques can be combined with high precision trace gas instrumentation to yield novel insights into these processes and their mechanisms.

We present measurements of a wide range of trace gases before, during, and after a simulated rainfall upon northeastern US temperature forest soil in meso-scale columns.  Subsurface concentrations and above-ground fluxes of N2O and its isotopes, CH4 and its isotopes, CO2, NO, NO2, NH3, and a wide range of volatile organic compounds (e.g. monoterpenes, sesquiterpenes, isoprene, acetonitrile, aromatics) were quantified in real time with 30 minute temporal resolution.  Small molecules were measured using Aerodyne TILDAS instruments, while VOCs were measured using a Vocus mass spectrometer.

Addition of water to the dried soil column produced a classic Birch effect pulse of both C and N species, including for VOCs.  We explore correlations between responses of trace gases above- and below-ground, and relate the small molecule pulses to the larger VOC responses.  In addition, we demonstrate the value of isotopic signatures for these studies, with the observation of fast, large isotopic shifts in the 15N2O isotopomers.  We compare these isotopic signatures to simple kinetic models to provide insight into the mechanisms underlying the nitrogen Birch effect.
A geospatial model for mapping desertification risk areas in the Caatinga biome, a semiarid region of Brazil
Authors: César Ferreira Marcos , Monteiro Navarro de Oliveira Mariana , Carneiro Valente Danilo
Published: March 2020

Desertification is a process characterized by the degradation and drying of soils in arid, semiarid and subhumid regions that results from a combination of climatic factors and human activities. This process influences the productivity potential of the soils, impacting the populations residing in the affected areas, and may cause long-term economic problems and impacts on human health, such as hunger and food insecurity. The aim of this paper is to present a geospatial model for mapping desertification risk areas in northeastern Brazil. The test area for the model was located in the Brazilian semiarid climatic region in the state of Ceará. In this area, the dry season lasts for 7 to 8 months, and the original vegetation belongs to the Caatinga biome. The model was based on algebraic operations between maps of environmental variables, performed in a geographic information system, and based on equations obtained through logistic regression analysis. First, 300 points were mapped in the centroids of desertification polygons (D), and 300 points were mapped in areas where no desertification processes (ND) had occurred. All points were selected by visual interpretation of Sentinel-2A multispectral images. Then, 500 m radius buffers were mapped around the centroids of the D and ND areas, and the mean values of the following environmental variables were extracted within these buffers: the average annual rainfall (RAIN), altitude (ELV), vegetation index dry season (VID), wet season vegetation index (VIM), dry season soil temperature (LTD), and wet season soil temperature (LTM). The mean values ​​of the RAIN, ELV, VID, VIM, LTM and LTD variables for the D and ND areas were entered in the MedCalc software for logistic regression analysis. The p probability map of desertification occurrence was constructed in ArcGIS Pro using equations for which the parameters were obtained with the logistic regression analysis. The results showed that the variables RAIN, ELV, VID and LTD (p <0.0001) contributed significantly to the occurrence of desertification areas. The value obtained for the area under the ROC curve (AUC) parameter was 0.757, and the percentage of cases correctly classified by the model was 70.17%. In the next step of this research, this model will be tested on a larger area of 72,000 km2 that is located in the Jaguaribe River basin, northeastern Brazil.
Teleconnections between ENSO and hydrological response at the catchment-scale in Central-Southern Chile
Authors: Hernandez Diego , Ricchetti Franco , Mendoza Pablo , Vargas Ximena
Published: March 2020

Despite the large evidence on teleconnections between the El Niño South Oscillation (ENSO) phenomenon and the hydroclimatology of Central-Southern Chile, the propagation of the ENSO signal through the hydrological cycle is still unclear, because of the complex hydrological processes and compensatory/amplifying effects of meteorological anomalies on the hydrology. In this work, we examine the sensitivity of hydrological responses to contrasting ENSO phases – El Niño, La Niña or neutral phase – against local climatic conditions across 55 near-natural catchments, whose location provides a strong north-south latitudinal dry-wet gradient, with the Andes Cordillera acting as a longitudinal elevation control. We analyze the dependence of four meteorological variables and four hydrological signatures with ENSO phases across three different hydrological regimes – snowmelt-dominated, rainfall-dominated and mixed –. Additionally, we calculate the sensitivity of hydrological signatures to meteorological variables as the total derivative, to assess the full interactions of the system.

Our results confirm statistically significant anomalies of streamflow and meteorological variables at the catchment-scale according to ENSO phases. Hydrological regimes (i.e. seasonality) are enhanced during El Niño years, showing a clear latitudinal gradient. We obtain negative (positive) sensitivities of non-dimensional annual streamflow to increased mean winter temperature at higher (lower) elevations, but positive sensitivities to mean winter storm temperature in the entire study domain. We advise these different sensitivities of non-dimensional annual streamflow – to mean winter storm temperature compared to the whole winter mean temperature – may depict different hydrological implications. We confirm positive (negative) streamflow anomalies with El Niño (La Niña) phases, and we note concomitancy in snowmelt-dominated basins with lesser (higher) runoff ratio anomalies. In rainfall-dominated basins, we obtain higher (lower) runoff ratio anomalies with El Niño (La Niña) phases. This is, for snowmelt-driven/semiarid basins, we note compensatory anomalies between annual streamflow and runoff ratio, and our results suggest that runoff ratio anomalies may be driven by precipitation anomalies rather than by temperature anomalies.
Isotopic evidence for changes in the origin and cycling of nitrogen in the Labrador Sea during the last 8,000 years
Authors: Kienast Markus , Davin Sam , Doering Kristin , Hebbeln Dierk , Kienast Stephanie , Lehmann Nadine , Schneider Ralph , Sherwood Owen , Weiser Jens
Published: March 2020

Subsurface nitrate in the Labrador Sea (NW Atlantic) and Baffin Bay is provided by North Pacific water flowing through Bering Strait and the Canadian Arctic as well as by advection from the North Atlantic. Both these nitrate sources are distinct in their isotopic signature (δ15N), owing to benthic denitrification on the Bering, Chukchi and east Siberian shelves and nitrogen fixation in the North Atlantic, respectively. Accordingly, water column profiles of δ15N(nitrate) collected off Greenland in the eastern Labrador Sea show low δ15N(nitrate), which mixes with more 15N-enriched nitrate flowing through Baffin Bay into the northern Labrador Sea. The Labrador Current carries this mixture southward along the western Labrador Sea, toward Newfoundland. The δ15N of surface sediments in the Labrador Sea closely mirrors these water column signals, suggesting that sediments can be used to trace changes in both the source signature of Atlantic versus Pacific-derived nitrate as well as in the admixture of the two source waters.

Two downcore sedimentary δ15N records from the NE and NW Labrador Sea coast both show high δ15N values of ca. 7‰ during the early Holocene (9-7 kyrs BP). In the NE Labrador Sea, this is followed by a long-term decrease toward δ15N of ca. 4.5‰ at the core top, in contrast to a much more subtle decrease in the NW Labrador Sea (surface sediment δ15N of ca. 6.5‰). The decreasing δ15N values along the eastern Labrador Sea are consistent with a Holocene increase in nitrogen fixation in the North Atlantic or an increasing advection of isotopically light nitrate. In turn, an increasing admixture of North-Pacific-derived nitrate, or intensified denitrification on the Bering Shelf would be required to explain the much subdued Holocene δ15N decrease in the NW Labrador Sea.
Deep Mantle Dynamics in East Asia: Numerical Simulation of Mantle Convection Based on Seismic Tomography
Authors: Zhang Huai , Zheng Qunfan , Zhang Zhen
Published: March 2020

East Asia is a tectonically active area on earth and has a complicated lithospheric deformation due to the western continental collision from the cratonic Indian plate and the eastern oceanic subduction mainly from Pacific plate. Studies have suggested that the Indo–Asian continental collision may have driven significant lateral mantle flow, but the velocity, range and effect of the mantle flow remain uncertain. Hence, a series of 3-D numerical models are conducted in this study to reveal the impacts of the Indo–Asian collision on mantle dynamics beneath the East Asia, especially on the asthenospheric mantle. Global model domain encompasses the lithosphere, upper mantle and the lower mantle with different viscosity for each layer. A global temperature structure built from seismic tomography and absolute plate field are applied subsequently to get a better constraint of the initial temperature condition and surficial velocity boundary condition. Thus, the reasonable velocity and temperature distributions of upper mantle beneath East Asia at different depths are retrieved based on our 3-D global mantle flow simulations, and the key controlling parameters in shaping the present-day observed mantle structure are investigated. The results show different scales of convection beneath East Asia.

Our results suggest that Indo–Asian collision may have induced mantle flow beneath the Indian plate and the different velocity structures between the asthenosphere and lithosphere indicate the shear drag of asthenospheric mantle. That may explain the reason that Indo–Asian collision has occurred since 50 Ma, and this collision can still continue to accelerate in the Tibetan Plateau. The simulation results also show the lithospheric delamination and the induced mantle upwelling, which is consistent with the general understanding from previous observations. The Indian lithosphere and its asthenosphere move northward, while the Yunnan lithosphere and its asthenosphere move southward, that may reflect the differences in deep mantle dynamics between the eastern and western Himalayan Syntaxis.
Exploiting the information in soil moisture and vegetation optical depth retrievals from passive microwave radiometry.
Authors: Kumar Sujay , Holmes Thomas , bindlish Rajat , de Jeu Richard , Peters-Lidard Christa
Published: March 2020

Historically, microwave radiometry has usually been used for retrieving estimates of soil moisture. As these measurements are also sensitive to vegetation, the attenuation of the microwave signal from vegetation, described by the vegetation optical depth (VOD) parameter can be used an analog of above-ground canopy biomass. This study explores the relative and joint utility of assimilating soil moisture and VOD retrievals from passive microwave radiometry within the NoahMP land surface model. The impact of assimilation on key water and carbon budget terms are quantified through comparisons against reference datasets. The results indicate that the assimilation of soil moisture retrievals has a positive impact on the simulation of surface soil moisture and little impact on evaporative fluxes. In contrast, VOD assimilation has significant impacts on the simulation of vegetation conditions, root zone soil moisture, and evapotranspiration (ET). Over water limited domains with sparse vegetation where soil moisture is the primary control on ET, the assimilation of surface soil moisture is more beneficial than VOD DA. In contrast, over regions with dense vegetation and where water availability is not limiting, transpiration has a significant influence on evapotranspiration. The assimilation of VOD is more beneficial in developing improvements in ET over such areas. The results of this study confirm that soil moisture and VOD retrievals provide independent information that can be jointly exploited through their simultaneous assimilation.

 

 
Time-dependent investigation of a slow-moving landslide in Los Angeles, CA, through SAR observations and numerical simulations
Authors: Necula Nicușor , Mohammadi Kami , Khoshmanesh Mostafa , Asimaki Domniki
Published: March 2020

As urbanized areas increasingly expand into mountainous terrains and climate change accentuates extreme weather conditions (rainfall or drought), slow-moving landslides increasingly threaten the resilience of infrastructure systems. Referred to as creeping landslides, these features may appear benign but can abruptly turn into catastrophic failures and debris flows during heavy rainfall or an earthquake. Because of the spatial extent and time evolution of ground deformation risk, conventional observation techniques such as site surveying, that rely on human resource availability and involve safety considerations, cannot be used to identify precursors of impending failures. Instead, remote sensing techniques for landslide monitoring such as differential SAR Interferometry (DInSAR) allow the spatiotemporal retrieval of surface changes with millimeter accuracy. We here test the reliability of repeat-pass interferometry techniques coupled with numerical models of creep to quantify the time-dependent deformations of a landslide in the Bel Air district of Los Angeles, USA. We validate our measurements and predictions by comparison with in-situ deformation profiles, and provide detailed representations of ground surface and subsurface displacements, along with the relationship between environmental factors and material properties. The wealth of in-situ measurements and site characterization data at the site improves our understanding of deformation precursors that can be used to minimize the risk posed to communities by slow-moving landslides.
Substantial gadolinium enrichments in lake and river near metrocities in Korea
Authors: Kim Intae , Kim Suk Hyun
Published: March 2020

We measured dissolved rare earth elements (REEs) in the water samples from Shihwa Lake (SL), which was assumed to be highly polluted, as well as in the downstream portion of the Han River (HR), which runs through, Seoul, Korea. Among the investigated REEs, only Gadolinium (Gd) was found to be significantly enhanced after REE concentrations were shale-normalized (SN). The calculated Gd anomaly (Gd/Gd* = 3×GdSN/(SmSN + 2×TbSN)) was about 1.5±0.1 (n=16) in SL and 1.6±0.3 in HR (n=26) water relative to other types of natural water such as groundwater, seawater, and river water in uncontaminated areas (Gd/Gd*~1.2, n>400). These significant Gd anomalies seem to be due to the inputs of anthropogenic Gd (Gdanth), especially by the use of Gd-based contrast agents for magnetic resonance imaging (MRI) tests from a number of hospitals and medical institutes surrounding our study areas. The Gdanth inventory was estimated to be 190±80 g and 680±360 kg Gd in SL and the HR (watersheds in our study area), respectively. The Gdanth flux to the Yellow Sea from the HR is estimated to be 530±330 g Gd day-1. Overall, these results suggest that quantitative evaluation of man-made REEs for associated human risk assessments are needed, because considerable amounts of REEs are now used by modern high-tech industries.
MAVEN Observations of Large-amplitude, Quasi-periodic Sawtooth-like Magnetic Field Oscillations Associated with Kelvin-Helmholtz Instability
Authors: Poh Gangkai , Espley Jared , Romanelli Norberto , Gruesbeck Jacob , DiBraccio Gina
Published: March 2020

In this study, we present a preliminary analysis of large-amplitude sawtooth-like magnetic field oscillations observed by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft at Mars. Initial survey of these quasi-periodic magnetic field oscillations (with periods of ~3 – 4 minutes) shows distinct sawtooth-like magnetic field signatures with steep increase in BY of ~20 – 30 nT, followed by a gentle, but turbulent, return to background magnetic field values. The extrema in the BY component generally coincide with an extrema of opposite polarity in the BX component. Quasi-periodic magnetic field signatures can also be observed in the z-component of the magnetic field vector. Ion and electrons measurements shows corresponding increase in ions and electrons with energies greater than 30eV and 10 eV, respectively, during observations of these sawtooth-like oscillations, indicating some mixing of plasma. We interpret these observations as Kelvin-Helmholtz (KH) waves in the non-linear stages because the plasma and fields signatures are consistent with non-linear KH waves observed at Earth and other planetary environments. KH waves are developed as a result of flow shear-driven KH instability occurring between the boundary separating two moving fluids. In the non-linear stage of the KH instability, rolled-up KH vortex can developed along the boundary, allowing the mixing of plasma between the two plasma regions. Occurrence of KH waves had been observed at Venus’ ionopause and the induced magnetopause, contributing to loss of planetary ions in the form of plasma clouds. Earlier simulations and observational studies have also explored the possibility of non-linear KH instability occurring at Mars. We will discuss the conditions required for the development of KH instability, its growth rate and implications on mass loss at Mars. Comparison with simulations will also be conducted and discussed.
Ultra-acid volcanic waters: origin and response on volcanic activity. A review
Authors: Taran Yuri , Kalacheva Elena
Published: March 2020

Some active volcanoes host thermal springs with ultra- (1<pH<2) and even hyper- (pH < 1) acidic waters with composition corresponding to a mixture of HCl and H2SO4 acids and with cations where Al and Fe are often the major components. Such springs sometimes are known as inferred drainages from active crater lakes (e.g., Rios Agrio at Poas and Copahue volcanoes). However, there are a number of acidic volcano-hydrothermal systems of Cl-SO4 composition at volcanoes without crater lakes.  At least ten groups of manifestation of this type are known for Kuril Islands. Several groups of acid volcanic springs including the famous Tamagawa springs are described in Japan.  Most of the acid Cl-SO4 volcano-hydrothermal systems are characteristic for island volcanoes, probably due to specific hydrological conditions of small volcanic islands. Maybe most known are coastal acid springs at Satsuma Iwojima volcano, Ryukyu arc, Japan. The accepted idea about the origin of such systems is scrubbing (dissolution) of magmatic HCl, HF and SO2 by groundwaters above magmatic conduits.  If so, the composition of acid springs must reflect the state of activity of a volcano. This review describes case histories that are known from the literature and from authors’ studies. Most of the volcanoes hosting acid systems show frequent phreatic activity. We show that  in contrast to crater lakes (Poas, Ruapehu, Copahue, White Island), acid springs on slopes of active volcanoes generally do not response on the preparing or ongoing volcanic eruptions. The aquifers and flow paths of the acid waters in volcanic edifices can be not associated with active conduits but with other degassing magmatic bodies and/or with deeper aquifers. One of the examples of such a complicated system is Ebeko volcano with Yuryevskye springs in Kuril Islands. These springs have a hydrochemical record since 1950s, and during this period Ebeko volcano had at least 10 strong phreatic eruptions.
Soil erosion and sediment interception by check dam in watershed under extreme rainstorm on the Loess Plateau, China
Authors: bai leichao
Published: March 2020

The magnitude of soil erosion and sediment reduction efficiency of check dams under extreme rainstorms are long-standing concerns. This paper aims to use check dams to deduce the amount of soil erosion under extreme rainstorms in watersheds and to identify the difference of sediment intercepting efficiency of different types of check dams. Based on the sediment deposition of 12 check dams with 100% sediment intercepting efficiency and sub-catchment clustering by taking 12 check dams-controlled catchments as standard separately, the amount of soil erosion caused by an extreme rainstorm event on July 26th, 2017 (named “7·26” extreme rainstorm) was deduced in the Chabagou watershed in the hill and gully region of the Loess Plateau. The differences of sediment intercepting efficiency among check dams in the watershed were analysed according to the field observation 17 check dams. The results showed that the average erosion intensity under the ‘7·26’ extreme rainstorm was approximately 2.03×104 t·km-2, which was 5 times that in the second erosive rainfall in 2017 (4.15×103 t·km-2) and 11-384 times that in 2018 (0.53×102 t·km-2 - 1.81×103 t·km-2). Under the ‘7·26’ extreme rainstorm, the amount of soil erosion in the Chabagou watershed above Caoping hydrological station was 4.20×106 tons. The sediment intercepting efficiencies check dams with drainage canals (including the destroyed check dams) and with drainage culverts was 6.48% and 39.49%, respectively. The total actual sediment amount trapped by the check dam was 1.11×106 tons, accounting for 26.36% of the total soil erosion amount. In contrast, 3.09×106 tons of sediment was inputted to the downstream channel, and the sediment deposition in the channel was 2.23×106 tons, accounting for 53.15% of the total amount of soil erosion. The amount of sediment transport at the hydrological station was 8.60×105 tons. The sediment delivery ratio (SDR) under the “7·26” extreme rainstorm was 0.21. The results indicated that the amount of soil erosion was huge, and the sediment intercepting efficiency of check dams was greatly reduced under extreme rainstorms. It is necessary to strengthen the management and construction technology standards of check dams to improve the sediment intercepting efficiency and flood safety in the watershed.
Natural carbon release over-rides anthropogenic carbon uptake when Southern Hemispheric westerlies strengthen
Authors: Spence Paul , Menviel Laurie , Waugh Darryn
Published: March 2020

The Southern Ocean is one of today's largest sink of carbon, having absorbed about 10\% of the anthropogenic carbon emissions. Southern Ocean's dynamics are principally modulated by the strength of the Southern Hemispheric westerlies,  which are projected to increase over the coming century. Here, using a high-resolution ocean-sea-ice-carbon cycle model, we explore the impact of idealized changes in Southern Hemispheric westerlies on the ocean carbon storage . We find that a 20\% strengthening of the Southern Hemispheric westerlies leads to a $\sim$25 Gt loss of natural carbon, while an additional 13 Gt of anthropogenic carbon is absorbed compared to the control run, thus resulting in a net loss of $\sim$12 GtC from the ocean over a period of 42 years. This tendency is enhanced if the westerlies are also shifted polewards, with a total natural carbon loss of almost 37 GtC, and an additional anthropogenic carbon uptake of 18 GtC. While both experiments display a large natural carbon loss south of 10$^\circ$S, the amplitude is three times greater in the poleward strengthening case, which is  not fully compensated by the increase in anthropogenic carbon content. However, the poleward wind shift leads to significant differences in the pattern of DIC change due to a weakening of the upper overturning cell,  which leads to an increase in natural and total carbon north of 35$^\circ$S in the upper 2000 m.
Effects of changing drainage networks on carbon storage capacity of Southeast Asian peatlands
Authors: Cobb Alex , Dommain René , Tan Fangyi , Heng Naomi , Harvey Charles
Published: March 2020

Since 1990, intact forest cover in tropical peatlands of western insular Southeast Asia has dropped to less than 10%.  Most deforested and degraded areas are also affected by drainage, which modifies most important ecological and biogeochemical processes, including carbon dioxide fluxes, methane fluxes, fire risk, and vegetational succession.  Therefore, in this region, peatland ecosystem processes and their response to anthropogenic change occur against the background of long-term spatial impacts from changing drainage networks. We build on earlier work on tropical peatland morphology to develop spatial predictions of the long-term effects of drainage network configuration on tropical peatlands.  We apply this analysis to examine the impacts of anthropogenic drainage on the capacity for carbon storage within natural and artificial drainage networks in Southeast Asia. With a case study, we then show how this approach can be used to produce quantitative estimates of how much peat will be lost or gained in the long term, and where, after drainage or restoration projects.
Counteracting global warming by using a locally variable Solar Radiation Management
Authors: Marchegiani Davide , Dommenget Dietmar
Published: March 2020

Solar Radiation Management (SRM) is regarded as a tool which could potentially mitigate or completely offset global warming by increasing planetary albedo. However, this approach could potentially reduce precipitation as well, as shown in the latest Intergovernmental Panel on Climate Change (ICPP) 5th report. Thus, although SRM might weaken global climate risks, it may enhance those in some regions. Here, using the Globally Resolved Energy Balance (GREB) model, we present experiments designed to completely offset the temperature and precipitation response due to a CO2-doubling experiment (abrupt2×CO2). The main idea around which our study is built upon is to employ a localized and seasonally varying SRM, as opposed to the most recent Geo-Engineering experiments which just apply a global and homogeneous one. In order to achieve such condition, we carry out the computation by using an “artificial cloud cover”. The usage of this localized approach allows us to globally cut down temperature warming in the abrupt2×CO2 scenario by 99.8% (which corresponds to an increase of 0.07 °C on a global average basis), while at the same time only having minor changes in precipitation (0.003 mm/day on a global average basis). To achieve this the cloud cover is increased by about 8% on a global average. Moreover, neither temperature nor precipitation response are exacerbated when averaged over any IPCC Special Report on Extremes (SREX) region. Indeed, for temperatures, 90% of SREX regions averages fall within 0.3 °C change, with all regional mean anomalies being under 0.38 °C. Whereas, as far as precipitation is concerned, changes go up to 0.01 mm/day for 90% of SREX regions, with all of them changing by less than 0.02 mm/day. Similar results are achieved for seasonal variations, with Seasonal Cycle (DJF-JJA) having no major changes in both surface temperature and precipitation.
The Formation Mechanism Of Mudflat Soil Aggregates Driven By Exogenous Organic Matters
Authors: Bai Yanchao , Gu Chuanhui , Shan Yuhua
Published: March 2020

Mudflats are valuable land resources located in the interaction zone between land and sea and are found in many parts of the world. The newly reclaimed mudflats are high in salinity and low in fertility as indicated by poor soil structure, extremely low organic matter content, low nutrient level and lack of microbial diversity, which is not suitable for cultivation. The keys to mudflat reclamation to arable lands are (1) to reduce salinity and (2) to increase the soil organic matter content and thus soil fertility. The former determines whether the reclaimed mudflat can be used for crop production and the latter determines whether the crop production is sustainable. On the basis of salt reduction measures, adding exogenous organic matter to drive the formation of soil aggregates in mudflat saline-alkali soil is a prerequisite for inhibiting the return of salt, improving fertility and promoting the transformation of mudflat reclaimed soil into arable soil. Research on the formation of clustered soil aggregates during the evolution of mudflat soil into arable soil should focus on the regulatory, formation, and stability mechanism of different exogenous organic matter. In addition, exploration of the effects of the special properties of mudflat soil, e.g., high salinity, high pH, and low microbial diversity, on the formation and stability of soil aggregates is necessary. The regularity and regulation of soil structure and fertility evolution of the mudflat driven by exogenous organic matter were clarified. Research on soil aggregate formation not only enrich the basic theory of soil quality evolution of mudflat, but also have practical guiding significance for the maturation of mudflat soil.