bluuebunny/crossref_metadata_2025 huggingface dataset:
Topographic effects on longwave and shortwave surface radiation in a kilometre-scale regional climate model
Authors: Steger Christian , Vergara-Temprado Jesus , Ban Nikolina , Schär Christoph
Published: March 2020

Weather and climate in alpine areas are strongly modulated by complex topography. Besides its influence on atmospheric flow and thermodynamics (such as orographic precipitation and foehn winds), topography also affects incoming surface radiation in various ways. Direct shortwave radiation might be blocked due to shading effects from neighbouring terrain. Diffuse shortwave radiation can be altered by a reduced sky view factor and reflectance of radiation from surrounding terrain. Similar, the net longwave radiation is affected by emissions from neighbouring terrain.

Radiation in virtually all state-of-the-art weather and climate models is only computed in the vertical direction using the column approximation, and the above-mentioned effects are usually not represented. Still, a few models consider topographic effects by correcting incoming radiation fluxes based on topographic parameters like slope aspect and angle, elevation of horizon, and sky view factor. The Consortium for Small-scale Modeling (COSMO) model includes such a scheme, which is currently only used in the Numerical Weather Prediction mode of the model.

In this study, we apply the surface radiation correction scheme in the climate mode of COSMO. To study its impacts in detail, we force COSMO’s land-surface model (TERRA) offline with output from a COSMO simulation, which was run without radiation correction at a horizontal resolution of 2.2 km and for a domain covering the Alps. A useful proxy to study the impact of the correction scheme is snow cover duration (SCD), because snow cover length is, amongst other factors, strongly controlled by incoming surface radiation that drives ablation. A comparison of SCD simulated by COSMO with satellite-derived snow cover data (MODIS and AVHRR) reveals a distinctive bias, where SCD is overestimated for south-facing grid cells and underestimated for north-facing cells. Applying the radiation correction in the offline TERRA simulation shows only a moderate reduction of the bias. One reason for this minor improvement is the fact that the topographic parameters are computed from a smoothed digital elevation model (DEM) – thus the impact of the radiation correction scheme is damped. If topographic parameters are computed from unsmoothed DEM, biases in SCD are further reduced. Currently, further sensitivity experiments are conducted to investigate the effect of computing the topographic parameters from a sub-grid DEM and to assess the energy conservation of the radiation correction scheme.
The Dynamic Motion of the OC4 Floating Turbine with Different Incident Wave and Wind Directions in a Mooring System Failure Condition in Numerical Model
Authors: Chuang Tzu-Ching , Yang Wen-Hsuan , Chen Yi-Hong , Yang Ray-Yeng
Published: March 2020

In this paper, the commercial software Orcaflex is used to simulate the motion behavior of the OC4 floating platform, and the floater stability and mooring line tension after the mooring system failure. In the time domain analysis, the discussion is divided into three phases—the first phase (before the tether failure), the second phase (before the tether failure, before reaching the new steady-state), and the third phase (after reaching the new steady-state). The motion characteristics and tension values at different stages were observed. In this study, only a 50-year return period wave condition is used as an input condition and simulating 11 different incident wind and wave directions. The numerical results are presented in the trajectory map and the table. About the tension of the mooring line, after the mooring system fails, it is notable that the mooring line tension will first decrease and then increase slightly above the initial tension value. In other words, the mooring system may survive after the failure of one mooring line and got a new balance of it. However, the tension amplitude will be higher than the first stage in the new balance and it will likely increase the risk of mooring line fatigue.
The Seismic Network of Zapopan: Evaluating the local seismicity of the western Guadalajara Metropolitan Zone
Authors: Núñez Diana , Núñez-Cornú Francisco J. , Alarcón Edgar , Quinteros-Cartaya Claudia B. M. , Suárez-Plascencia Carlos , Ramírez Sergio
Published: March 2020

The Municipality of Zapopan, Jalisco, is located west of the Guadalajara Metropolitan Zone at the intersection of three rift zones: Tepic-Zacoalco, Chapala-Tula, and Colima. The importance of this region lies in the recent population growth that it has experienced in a few years. This growth has been supported by the development in commercial and service activities, and mainly in industry and technology, being ranked as the second-most populous city in Mexico, behind the federal capital.

The western region of the Guadalajara Metropolitan Zone (GMZ) has numerous fault systems where, historically, there have been significant earthquakes and seismic swarms such as those that occurred in 1685-1687, 1875, 1932, 1995 and 2002, showing similar characteristics. Besides, it is in this region where the Caldera de la Primavera is located, a rhyolitic volcanic caldera that continues presenting seismic and geothermal activity.

Recently, in the years 2015 and 2016, new seismic swarms occurred and were recorded instrumentally for the first time by the Jalisco Seismic and Accelerometric Network (RESAJ). The two seismic sequences took place in two alignments in the same direction as the Colima rift. These epicenters suggest the existence of two almost parallel normal faults, and that would be forming the Graben of Zapopan. Due to the length of these faults, 16 km for the east fault, and 28 km for the west fault, earthquakes of magnitudes 6.2 - 6.5 could be generated.

In the framework of the CeMIEGeo P-24 project (SENER-CONACyT), we continue studying the seismicity of this region with the deployment of 25 seismic stations in the vicinity of La Caldera de la Primavera. This study revealed the high seismicity that was taking place in the area of ​​Zapopan, Tesistán Valley, and La Caldera de la Primavera.

Based on these new studies and the knowledge of the seismic history of the region, a collaboration agreement has been established between the Research Group UDG-CA-276 SisVOc and Civil Protection of the Municipality of Zapopan for the installation of a local seismic network that will allow to define tectonic and structurally the fault systems of the region and mitigate the possible effects of the local seismicity in the population. Since May 2019, three Obsidian 8X seismic stations with Lennartz 1Hz LE3D and Episensor sensors and two accelerometers installed in the city have been operating, constituting the Zapopan Seismic and Accelerometric Network (RESAZ). The RESAZ operates together with the nearest stations of the RESAJ. In this work, we present the first results of the seismicity analysis recorded in Zapopan.
Slip models of the 2016 Mw7.0 Kumamoto, Japan mainshock and its two foreshocks constrained by multi-mode InSAR data
Authors: Wang Yongzhe , Feng Wanpeng , Chen Kun , Du Hailin
Published: March 2020

Interferometric Synthetic Aperture Radar (InSAR) data is of high spatial resolution and has been widely used in measuring surface deformation generated by earthquakes. However, the temporal resolution of InSAR data is relatively poor from an individual mode SAR sensor. A series of earthquakes hit Kumamoto, Japan in April 2016. These earthquakes were considered to be a sequence that started from two foreshocks (TFS) larger than Mw 6.0 and reached its climax for the largest earthquake of Mw7.0 only after 28 hours. To better reveal the source model characteristics of the TFS and the main shock, we firstly determined the geometrical parameters using the aftershock re-location data and the surface fault rupture data of field survey, and then applied multi-mode InSAR data only covering the TFS and the whole sequence, respectively, to carry out the joint inversion of respective source models based on the time correlation between the TFS and the main shock. The results show that both the source models determined here are well consistent with previous results constrained by seismological data. The strategy of inversion used in this study suggests that we may separate multiple seismic sources sequence from geodetic observations using the joint inversion based on the time correlation.
Field analysis Vs boat-based photogrammetry derived data in volcanotectonics: an example from the Santorini dyke swarm
Authors: Drymoni Kyriaki , Bonali Fabio Luca , Browning John , Gudmundsson Agust , Fallati Luca , Antoniou Varvara , Nomikou Paraskevi
Published: March 2020

Field studies are vital for mapping and understanding active geological processes on Earth. Such studies commonly inform analogue and numerical modelling setups and provide insights over a variety of scales. However, geological field studies have several limitations as they are sensitive both to field-based conditions (e.g. weather conditions, geomorphology, weathering, erosion and access) and the experience of the researchers conducting the work. All of these limitations can add significant error or uncertainty to geological measurements. At the same time, new geological measurement techniques (e.g. photogrammetry) are easy to access, fast and friendly to use, but also often depend on ground truthing parameters.

In this study, we compared two different methods for mapping and surveying volcanotectonic processes related to dyking events: classical field analysis and boat-based photogrammetry. We tested the two approaches on dykes located within a section of a steep cliff face that makes up part of the Santorini caldera. The caldera wall is accessible by land only in the upper most parts and so most measurements require access by boat or by abseiling down the cliff faces. The latter is very dangerous and not recommended.

The core of the work is to carefully compare field data with the equivalents collected on photogrammetry-derived 3D model, focusing on the sea level area in order to compare reliable dataset. Data comparison is focused on dyke attitudes, thicknesses, petrological descriptions, along the 4-km length profile of the northern caldera wall of Santorini volcano.

We collected a series of high-resolution images, around 800 pictures in total, aimed at 3D modelling the dyke swarm using photogrammetry methods. They have been collected using a 20 MPX hand-held camera equipped with commercial GPS from a boat, moving parallel and to a constant distance from to the caldera wall.

Comparison of both datasets allowed insights into 1) the completeness and, 2) the limitations of each technique. Here we assess the various advantages to design a novel multidimensional methodology that allows fast, accurate and low-cost data generation in difficult working conditions, such as at steep cliff faces and flooded terrains.
A Random-Forest approach to predicting preferential-flow snowpack runoff: early results and outlook for the future
Authors: Johnson Ryan , Oroza Carlos , Avanzi Francesco , Satoru Yamaguchi , Hirashimia Hiroyuki , Maurer Tessa
Published: March 2020

Predicting the occurrence of preferential-flow snowpack runoff as opposed to spatially homogeneous matrix flow has recently become an important topic of cryosphere research, because of its implications for better understanding and forecasting wet-snow avalanche formation, streamflow generation during rain-on-snow events, and the polar-sheet water balance. Using twelve seasons of daily data from nine multi-compartment snow-lysimeters and concurrent weather and snowpack observations, we explored the accuracy of a machine-learning algorithm, Random Forest, in predicting the occurrence of preferential-flow snowpack runoff in a maritime context where sub-freezing conditions are rare (Nagaoka, Niigata prefecture, Japan). The algorithm was trained to predict three metrics of preferential-flow snowpack runoff: the coefficient of variation and standard and maximum deviations from mean spatial snowpack runoff. Two validation scenarios were used: one in which data were randomly subsampled from the entire period of record (66% training data, 33% testing), and a leave-one-year-out scenario, in which the model was trained on 11 years and tested on an unseen year. The latter was intended to represent a more realistic scenario in which limited data are available. Five tiers of features were used as inputs (independent variables) to the algorithm, including concurrent weather and bulk-snow properties, snow-atmosphere energy-balance components, internal snow structure, simulated matrix-flow snowpack runoff, and a selection of the five most important features from all previous groups. Relatively high model performance (Nash-Sutcliffe-Efficiency, NSE, > 0.53) was observed in all all-year scenarios, whereas the leave-one-year-out scenario displayed nearly a 50% reduction in performance, indicative of an inconsistent relationship across weather, snow conditions, and preferential-flow snowpack runoff generation between seasons. Random Forest also underestimated seasonal peaks in preferential flow, indicative of under-sampling in the dataset or unrepresented processes exceeding the spatial scale of multi-compartment lysimeters. This research presents an initial framework for understanding key factors influencing preferential-flow occurrence; improvements in algorithm accuracy could support predictions of preferential-flow snowpack runoff, especially in sparsely monitored regions.
Different Sources of 10-30-day Intraseasonal Variations of Autumn Snow over Western and Eastern Tibetan Plateau
Authors: Song Lei
Published: March 2020

Using the latest daily MODIS satellite snow cover data, the present study reveals distinctly different sources of 10-30-day intraseasonal snow cover variations over the western and eastern Tibetan Plateau (TP) during September-December. The intraseasonal snow variation over the western TP is related to a mid-latitude wave train associated with the Arctic Oscillation and that over the eastern TP is related to a subtropical wave train triggered by the North Atlantic Oscillation. The Rossby wave train in both cases leads to anomalous water vapor convergence and ascending motion, which contributes to snow accumulation and positive snow cover anomalies. For the western TP snow events, the moisture comes from the Caspian Sea. During the eastern TP snow events, the moisture originates from the Bay of Bengal.
Applying Non-Random Block Cross-Validation to Improve Reliability of Model Selection and Evaluation in Hydrology: An illustration using an algorithmic model of seasonal snowpack
Authors: Luce Charles , Lute Abigail
Published: March 2020

A central question in model structural uncertainty is how complex a model should be in order to have greatest generality or transferability.  One school of thought is that models become more general by adding process subroutines.  On the other hand, model parameters and structures have been shown to change significantly when calibrated to different basins or time periods, suggesting that model complexity and model transferability may be antithetical.  An important facet to this discussion is noting that validation methods and data applied to model evaluation and selection may tend to bias answers to this question.  Here we apply non-random block cross-validation as a direct assessment of model transferability to a series of algorithmic space-time models of April 1 snow water equivalent (SWE) across 497 SNOTEL stations for 20 years.  In general, we show that low to moderate complexity models transfer most successfully to new conditions in space and time.  In other words, there is an optimum between overly complex and overly simple models.  Because structures in data resulting from temporal dynamics and spatial dependency in atmospheric and hydrological processes exist, naïvely applied cross-validation practices can lead to overfitting, overconfidence in model precision or reliability, and poor ability to infer causal mechanisms.  For example, random k-fold cross-validation methods, which are in common use for evaluating models, essentially assume independence of the data and would promote selection of more complex models.  We further demonstrate that blocks sampled with pseudoreplicated data can produce similar outcomes.  Some sampling strategies favored for hydrologic model validation may tend to promote pseudoreplication, requiring heightened attentiveness for model selection and evaluation.  While the illustrative examples are drawn from snow modeling, the concepts can be readily applied to common hydrologic modeling issues.
Water security for subjective wellbeing: new perspectives for sustainable development
Authors: Roder Giulia , Chapagain Saroj Kumar , Hudson Paul , Mohan Geetha , Fukushi Kensuke
Published: March 2020

The notion of sustainable development in the current policy environment is inescapable from the concept of human wellbeing, as linked to the civic, political, economic, and natural environments people live in. However, the latter has been quite often overlooked in the scientific discussion, whereas nature’s ability to support and expand human capabilities and activities is essential for sustainable development. In this context, water is a crucial resource and has an immeasurable value in both economic and non-economic roles, with a deep spiritual significance in many cultures as well. However, access to clean water to meet basic needs is precluded in many countries in the world. This inaccessibility puts entire communities in jeopardy, thus impacting their happiness and sustainable living and development. A large proportion of the Nepalese society is bereft of access to adequate and safe drinking water, challenging the availability of this scares resource and its management in the future.

For this reason, we are undertaking 650 face-to-face interviews to understand peoples’ subjective wellbeing related to water in Pokhara metropolitans city, the second-largest city of Nepal. Preliminary results from the pre-test (n=50) demonstrated a modest sense of place and happiness overall but was impacted by the perceived unsatisfactory water quality. People strongly expressed a desire for new political commitment towards the creation of new regulatory approaches concerning water quality standards and management strategies. The pre-test respondents validated their support for increasing the quality of the water environment in the local water supply system by offering to pay an extra surcharge (in taxes or water bills), which is up to the double of their current expenses. These partial results suggest that the good quality of water is essential for the future urban planning in the form of increase people health and secure a sustainable development for future generations to come.
Long-term warming of Holocene winter temperatures in the Canadian Arctic recorded in stable water isotope ratios of ice wedges
Authors: Porter Trevor , Holland Kira , Froese Duane , Kokelj Steven
Published: March 2020

Rapid and sustained warming of the northern high latitudes has led to increased permafrost thaw and retrogressive thaw slump (RTS) activity in some areas of the Arctic. Thaw slumps are common in the Tuktoyaktuk Coastlands (Northwest Territories, Canada) and expose relict ice wedge polygon networks that contain a long-term record of winter precipitation isotopes. Notably, the stable isotope geochemistry of ice wedges can be used as a paleotemperature proxy for the winter season, a seasonality that is largely missing from current understandings of Holocene paleoclimate change in the Arctic.

 

In this study, we sampled lateral cross-sections of four relict ice wedges from RTS exposures at coastal sites on Hooper Island, Pelly Island, Richards Island and near Tuktoyaktuk. Ice blocks capturing the entire growth sequences of the ice wedges (i.e., ice wedge center to ice-sediment contact) were collected by chainsaw and kept frozen in field coolers, and later sub-sampled at high-resolution in a cold lab. The ice wedges were sub-sampled at 1-1.5 cm horizontal resolution, integrating ~1-3 ice veins per sample on average. We analysed the stable hydrogen- and oxygen-isotope ratios (δ2H and δ18O) of each sample (N = 803). The age of the ice was estimated by AMS-DO14C dating of 6 to 10 samples per ice wedge, evenly distributed across each wedge to capture the full range of ages. A composite δ18O record spanning the period 7,400-600 cal yr BP was also constructed using the dated samples only (N = 36). The all-sample co-isotope (δ2H-δ18O) data are defined by regression line that is remarkably similar to the Local Meteoric Water Line, suggesting the ice wedges reliably preserve the isotopic composition of local precipitation, which is strongly influenced by mean air temperatures. The composite record shows an increase in δ18O over the last 7,400 years which we interpret as a long-term warming trend of the mean winter climate. This warming trend is largely explained by increasing November-April insolation at 69°N, a result that is corroborated by two independent high-resolution ice wedge records from the Siberian Arctic and is also in agreement with model-based simulations of the winter climate. This record, the first of its kind in the North American Arctic, provides a more seasonally holistic perspective on Holocene climate change and highlights the potential to use permafrost isotope records to fill paleoclimate knowledge gaps in Arctic regions were more traditional precipitation isotope archives (e.g., ice cores) do not exist.
Putting Data to Work: ESIP and EarthCube working together to trasform geoscience
Authors: Robinson Erin
Published: March 2020

We believe that society's quality of life, economic opportunities, and stewardship of the planet are enhanced by regular use of scientifically sound Earth science data and information provided in a timely manner by a community that is collaborating to improve their collective services. The Earth Science Information Partners (ESIP) and the NSF EarthCube initiative have worked together over the last seven years to find alignment across distributed data networks.

As we enter the last three years of this decade-long EarthCube experiment, ESIP and the EarthCube Office (ECO) are building on the foundational work done over the last seven years, taking steps to provide continuity to the existing EarthCube community while looking toward the future to expand EarthCube’s reach across geosciences disciplines. Fundamental work includes designing outreach and education activities for researchers interested in acquiring the skills needed to ensure their data practices are Findable Accessible Interoperable Reusable (FAIR) and beyond.

This year we will focus on the theme: 'Putting Data to Work.' By increasing development and access to technology innovations, and nurturing a community of technically-savvy and engaged geoscientists through outreach activities like society meeting Data Help Desks, training and increased visibility. By building data stewardship capacity and working together across domains in the geoscience research ecosystem we will do better science, leaving a lasting legacy from EarthCube of fundamentally transforming geoscience.  
The NASA Atmospheric Tomography Mission: A Global-Scale Survey of Composition, Reactivity, and Transport in the Remote Atmosphere
Authors: Thompson Chelsea ,   The ATom Science Team
Published: March 2020

     The last seventy years have witnessed a marked acceleration of the impact of human activity impacting the planet due to the combination of rapid population growth, increased consumption of resources, and technological development. Nearly the entire human population occupies an astonishingly small percentage of the Earth’s surface, yet the imprint of human activity is being recorded in global climate and is perturbing the chemistry and composition of the most remote stretches of the atmosphere. These remote regions are exceptionally important for global air quality and climate (accounting on average for 75% of global CH4 removal, 59% of chemical production of O3, and 68% of chemical destruction of O3), yet the paucity of observations over the remote oceans have limited our understanding of these fundamental processes and their sensitivity to increased human perturbation.

     The NASA Atmospheric Tomography Mission (ATom) was designed to address these gaps in our understanding of chemical composition, reactivity, and transport through a combination of extensive measurements and photochemical modeling, and to provide much needed observational data from the remote regions of the atmosphere to provide rigorous tests that will lead to improvements in our global chemistry-climate models and to validate remote sensing retrievals. From 2016-2018, ATom utilized the fully instrumented NASA DC-8 research aircraft to collect an unprecedented suite of measurements of trace gases, aerosols, and key radical species from the remote troposphere and lower stratosphere.  Four complete pole-to-pole global circuits (one in each season) were conducted by performing near-continuous vertical profiles between 0.2 – 14 km altitude along meridional transects of the Pacific and Atlantic Ocean Basins. The data provided by this project have already led to several significant new findings, with many more on the horizon as research teams continue to uncover the full value of this dataset. In this talk, we will provide an overview of the ATom mission and discuss some of the major outcomes and new findings that have resulted from this project to date.
Linking decay of microbial mats and dolomite formation in the sabkhas of Qatar
Authors: Diloreto Zach , Dittrich Maria , Bontognali Tomaso , Al Saad Al Kuwari Hamad , A. McKenzie Judith
Published: March 2020

The sabkhas of Qatar are excellent environments to examine the mechanisms of low-temperature dolomite precipitation. The detailed microbial and geochemical analysis of the dynamics in environmental conditions in two microbial mats over two years provide a unique opportunity to gain insights in low-temperature dolomite formation in modern time. The compositions of extracted exopolymeric substances (EPS)  in two microbial mats, one within the lower intertidal zone and one within the upper intertidal zone exhibit an increase in the concentration of carboxylic functional groups during periods of elevated salinity. We interpret it as an indicator for dolomite formation since carboxylic functional groups are suggested to be the primary drivers for low-temperature dolomite as nucleation sites and inhibitors of Mg complexes. Notably, the increase in the concentration of the carboxylic group is associated with an increase in salinity in sabkha which happened periodically.

These fluctuations have been accompanied by the changes in the community from cyanobacterial dominated mat to one dominated by heterotrophs. During these periodical events, when a growing microbial mat turned into degrading microbial mat, we observed low-temperature dolomite formation. Such events occur in other modern dolomite forming environments and possibly in ancient sequences. Our work observed dynamical changes both in microbial mats, exopolymeric substances composition, geochemical gradients and accompanied low-temperature dolomite formation over several seasons. Our findings proving evidence that EPS degradation within microbial mats is a key mechanism in the formation of modern and most probable, ancient low-temperature dolomite with implications for those formed in ancient sequences.
Time Synchronization Method Based on Real-Time Precise Point Positioning
Authors: Lyu Daqian , Dong Tianbao , Zeng Fangling , Ouyang Xiaofeng
Published: March 2020

Precise point positioning (PPP) technique is an effective tool for time and frequency applications. Using phase/code observations and precise products, the PPP time transfer allows an accuracy of sub-nanoseconds within a latency of several days. Although the PPP time transfer is usually implemented in the post-processing mode, using the real-time PPP (RT-PPP) technique for time transfer with the shorter latency remains attractive to time community. In 2012, the IGS (International GNSS Service) launched an open-access real-time service (RTS) project, broadcasting satellite orbit and clock corrections on the Internet, which enables PPP time transfer in the real-time mode. In this contribution, we apply the RT-PPP for high-precision time transfer and synchronization. The GNSS receiver is required to be equipped with an atomic clock as the external local clock. We use the RT-PPP technique to compute the receiver clock offset with respective to the GNSS time scale. On the basis of clock offsets, we steer the local clock by frequency adjustment method. In this way, all the local clocks are synchronized to the GNSS time scale, making local clocks synchronized with each other.

The time scales of the RTS products are evaluated at first. Six kinds of the RTS products (IGS01, CLK10, CLK53, CLK80 and CLK93) on DOY220-247, 2019 are pre-saved to compute the receiver clock offsets. The clock offset with respect to the GPST (GPS Time) obtained from the IGS final product is applied as the reference. The standard deviations (STDs) of the clock offsets with respect to the reference are 0.63, 1.76, 0.28, 0.27 and 1.28 ns for IGS01, CLK10, CLK53, CLK80 and CLK93, respectively.

Finally, we set up a hardware system to examine the validity of our time synchronization method. The baseline of the time synchronization experiment is about 5 m. The synchronization error of the 1 PPS outputs is precisely measured by the frequency counter. The STD of the 4-days results is about 0.48 ns. The peak-to-peak value of the synchronization error is about 2.5 ns.
Influence of infiltration on Babaoliao shallow landslide in Taiwan using hydro-mechanical coupled model
Authors: Yang Ya-Sin , Yeh Hsin-Fu
Published: March 2020

Babaoliao landslide is located in Chiayi County of Taiwan. The geological drilling and core interpretation in previous investigation showed that exist 1 to 2 meter depths of residual soil layer above the bedrock. In this area, shallow landslides frequently occur due to the intense rainfall events. An understanding of the hydro-mechanical change under rainfall infiltration within hillslope is critical to capture the slope stability. This study used hydro-mechanical coupled model and finite element analysis to compute the field water content and stress suction, and then assess the field slope stability based on theory of local of factor. Results showed the response of internal hydraulic behavior distribution is related to terrain and the depths of bedrock. The impact of rainfall on slope stability concentrated in shallow residual soil area, since higher permeability of soil cause rainfall infiltrate into hillslope easily and form lateral flow paths, thus limiting the depths of wetting front. The discontinuity of water content distribution within hillslope may accelerate the change of hydro-mechanical behavior and unstable slope development in the hillslope. This study demonstrated the varied distribution of water content, suction stress and LFS over time and space and got the insight into the relativity unstable range of the shallow slope affected by rainfall event.
Improved daily accuracy from a new VIIRS-based, near-real time GFED emissions product
Authors: Andela Niels , Morton Douglas C. , van der Werf Guido R. , Schroeder Wilfrid , Giglio Louis , Chen Yang , Randerson James T.
Published: March 2020

 

Biomass burning on natural and agricultural lands has profound effects on atmospheric chemistry, climate, and air quality. Over the past decade, a number of global fire emissions inventories have been developed based on near-real time detection of actively burning fires by the MODIS instruments. However, the MODIS instruments provide variable and incomplete global sampling of fire activity, resulting in large uncertainty in the spatiotemporal accuracy of daily emissions inventories. Here, we compared active fire products from MODIS and VIIRS to characterize product-specific shortcomings of each system with the goal to develop a new, more accurate, global emissions inventory. The VIIRS 375m product was most sensitive to global fire activity and detected up to 55% more energy release from fires than the comparable 1km MODIS product in the tropics. Differences originated from improved coverage, sensitivity to low energy fires, and a more consistent cross-track spatial resolution. Nevertheless, both MODIS and VIIRS instruments showed reduced sensitivity to low energy fires at larger off-nadir angles, resulting in a cyclical pattern of daily fire detections and an underestimate of low energy fires, the dominant fire-type in shoulder seasons and more densely populated regions. Starting in 2018, the constellation of VIIRS instruments aboard NOAA-20 and SNPP provide improved near-nadir coverage, largely eliminating issues originating from incomplete sampling of low-energy fires at the edge of the VIIRS image swath. Based these findings, we developed a new near-real time emissions inventory that is spatially consistent with the GFED4s data record (1997-2016). Spatial allocation of emissions in the new GFED near-real time product differ considerably from existing daily emissions inventories, highlighting how different methodologies redistribute emissions across natural and human dominated landscapes based on daily active fire detections. Using column observations of NO2 and daily fire expansion rates from USGS, we demonstrate that the new, VIIRS-based daily fire emissions product provides more consistent spatial and temporal distribution of fire emissions compared to systems based on MODIS active fire detections. Improved accuracy is critical for air quality forecasts, source attribution, and the development of management strategies to minimize impacts on society.
Relationship between land use change and agricultural production in Chinese Yellow River Basin
Authors: Liu Jingjing , Wang Jing , Fang Ying , Li Zehui
Published: March 2020

The Yellow River basin, from west to east through different gradient terrains and climates, has huge spatial differences of land use and problematic eco‐environment. The understanding of relationship between land use change and agricultural production is crucial for coordinating the conflict between land development and environment protection in the Yellow River basin. In this study, the relationship between changes in arable land and urban land and changes in vegetation cover and agricultural production potential were quantitatively analyzed. Whether reclaimed land in the Yellow River basin can be converted to arable land and whether the occupation of urban land will cause ecosystem degradation were also discussed. The results indicated that: (1) Land use change in the Yellow River basin was greatly influenced by precipitation, which also affected the agricultural production potential and the Normalized Difference Vegetation Index (NDVI) in the Yellow River basin. The implementation of the Grain for Green program (GGP) had an effective restoration for vegetation cover and the resistance of soil erosion. Although the net area of arable land decreased by 71.6 ten thousand ha, the net production potential of arable land still increased by 1.7 ten thousand tons due to the inferior quality of the arable land for ecological restoration. (2) The concentrated distributed grassland and forest shrunk and the supply of ecosystem services and NDVI reduced, leading to ecological degraded in urban agglomeration regions where human activity was concentrated and construction land was increasing rapidly during the period of 2000–2015. The arable land was reduced by 43.3 ten thousand ha due to urban expansion, accounting for 59% of the total area of urban expansion, and consequently the agricultural production potential in the lower reaches was decreased. (3) Although it has not contributed significantly to agricultural production, the reclaimed land can be converted to arable land to a certain extent, due to its reasonable use for improving the ecological status of the Yellow River basin. 34.1 ten thousand ha of unused land and grassland were reclaimed for arable land under the Requisition‐Compensation Equilibrium of Farmland, which accounts for 1.27% of the total arable land. The increase of potential productivity brought by the reclamation of land for agricultural use only accounts for 0.56% of the total arable land potential productivity. However, compared with the whole Yellow River basin and the GGP region, the region with arable land reclaimed by low-coverage grassland and unused land leads to the highest increasing rate of the supply of ecosystem services and NDVI. The results could provide theoretical support and decision-making basis for further eco‐environment reconstruction, and promoting the reasonable land use and high-quality development in the Yellow River basin.
Modeling falling groundwater head declines in major cities of the world: current situation and future projection
Authors: Sutanudjaja Edwin
Published: March 2020

Over-consumption groundwater use is one of the major drivers in the hydrology of many major cities in the world, particularly in delta regions. However, a global assessment to identify cities with declining groundwater table problems has not been done yet. In this study we used the global hydrological model PCR-GLOBWB (10 km resolution) to do so. Using this model, we calculated groundwater recharge and river discharge/surface water levels, as well as groundwater abstraction. The output of PCR-GLOBWB model was then used to force a groundwater MODFLOW-based model simulating spatio-temporal groundwater head dynamics, including groundwater head declines in all major cities - mainly in delta regions - due to escalation in abstraction of groundwater to meet increasing water demand. Using this approach, we managed to identify a number of critical cities having groundwater table falling rates above 25 cm/year - average in the period 2000-2010 - such as Jakarta, Barcelona, Houston, Los Angeles, Mexico City, Rome and many large cities in China, Libya, India and Pakistan, as well as in the Middle East and Central Asia regions. However, our results overestimate head declines in Tokyo and some other places where groundwater depletion has been aggressively managed (e.g. groundwater abstraction has been minimized and replaced by importing surface water from other places). 

Currently, we are expanding this modeling simulation for the future period (i.e. until 2100), considering different climate scenarios (RCPs: 4.5 and 8.5) and socio-economic conditions (SSPs: 2 and 5). Our simulation results show that new and more cities with falling groundwater head problems would occur in the future, not only due to climate change (i.e. in areas that become dryer), but also due to increasing population, as well as expansion of existing urban areas and development of new urban areas.
Upper mantle viscosity structure and lithospheric thickness of Antarctica inferred from recent seismic models
Authors: Wiens Douglas , Lloyd Andrew , Shen Weisen , Nyblade Andrew , Aster Richard , Wilson Terry
Published: March 2020

Upper mantle viscosity structure and lithospheric thickness control the solid Earth response to variations in ice sheet loading. These parameters vary significantly across Antarctica, leading to strong regional differences in the timescale of glacial isostatic adjustment (GIA), with important implications for ice sheet models.  We estimate upper mantle viscosity structure and lithospheric thickness using two new seismic models for Antarctica, which take advantage of temporary broadband seismic stations deployed across Antarctica over the past 18 years. Shen et al. [2018] use receiver functions and Rayleigh wave velocities from earthquakes and ambient noise to develop a higher resolution model for the upper 200 km beneath Central and West Antarctica, where most of the seismic stations have been deployed. Lloyd et al [2019] use full waveform adjoint tomography to invert three-component earthquake seismograms for a radially anisotropic model covering Antarctica and adjacent oceanic regions to 800 km depth. We estimate the mantle viscosity structure from seismic structure using laboratory-derived relationships between seismic velocity, temperature, and rheology. Choice of parameters for this mapping is guided in part by recent regional estimates of mantle viscosity from geodetic measurements. We also describe and compare several different methods of estimating lithospheric thickness from seismic constraints.

The mantle viscosity estimates indicate regional variations of several orders of magnitude, with extremely low viscosity (< 1019 Pa s) beneath the Amundsen Sea Embayment (ASE) and the Antarctic Peninsula, consistent with estimates from GIA models constrained by GPS data.  Lithospheric thickness is also highly variable, ranging from around 60 km in parts of West Antarctica to greater than 200 km beneath central East Antarctica. In East Antarctica, several prominent regions such as Dronning Maude Land and the Lambert Graben show much thinner lithosphere, consistent with Phanerozoic tectonic activity and lithospheric disruption. Thin lithosphere and low viscosity between the ASE and the Antarctic Peninsula likely result from the thermal effects of the slab window as the Phoenix-Antarctic plate boundary migrated northward during the Cenozoic. Low viscosity regions beneath the ASE and Marie Byrd Land coast connect to an offshore anomaly at depths of ~ 250 km, suggesting larger-scale thermal and geodynamic processes that may be linked to the initial Cretaceous rifting of New Zealand and Antarctica. Low mantle viscosity results in a characteristic GIA time scale on the order of several hundred years, such that isostatic adjustment occurs on the same time scale as grounding line retreat.  Thus the associated rebound may lessen the effect of the marine ice sheet instability proposed for the ASE region. 
Modelling the responses of extreme events hydrometeorological events in the landslides and floods of the Combeima river basin.
Authors: Garzon Useche Laura Viviana , Santos Granados German Ricardo , Corzo Perez Gerald Augusto
Published: March 2020

The village of Juntas has a periodic sequence of hydrometeorological extreme events. The region present a tropical vegetation with a highly dynamic weather. Currently modelling of hydrological events have been limited to the use of conventional rainfall runoff models, that fail to represent accurately the moment when landslides start to occur, as well as to not be able to provide a clear spatial sensitivity of the relationship between landslide event and precipitation. This research presents a contribution in the linking of various modelling concepts to understand more the influence of the spatial variability of rain in the generation of the events. The data avaialable was daily precipitation during 15 years from de satelital imagine and the discharge of geotechnical characterizations, hydraulic analysis, ecological structures, cartography, vulnerability, flood and torrential risk maps.

The analysis is done by combining the information available in remote sensing rasters and the overall temporal relation of events is mapped with a spatiotemporal analysis of the extremes. The current methodology is expected to contribute to the understanding of the sensitivity of landslides due to the spatiotemporal variation of rain in the region.
Effects of Sensor Response and Gust Duration on Maximum Wind Gust Measurements and Data Homogenisation
Authors: Safaei Pirooz Amir Ali , Flay Richard G.J. , Minola Lorenzo , Azorin-Molina Cesar , Chen Deliang
Published: March 2020

Wind speed data recorded using different signal-processing procedures can introduce errors in the wind speed measurements. This study aims to assess the effects of a set of various moving average filter durations and turbulence intensities on the recorded maximum gust wind speeds. For this purpose, a series of wind-tunnel experiments was carried out at the University of Auckland, New Zealand, on the widely-used Vaisala WAA151 cup anemometer. The variations of gust and peak factors, and turbulence intensities measured by the cup anemometer as a function of the averaging duration and turbulence intensity are presented. The wind-tunnel results are compared with values computed from a theoretical approach, namely random process and linear system theory, and the results were also validated against values reported in the literature where possible.

To summarise, the major findings of this experimental study are:

The results show that increasing the effective gust duration reduces both the gust and peak factors, resulting in an underestimation of maximum gust wind speeds and an overestimation of minimum gust wind speeds.

The maximum difference between gust factors obtained for high (e.g. 3-s to 5-s) and low (raw, unfiltered measurements) gust durations reached values of 25% – 30% for the high turbulence conditions, and up to 5% – 10% for low turbulence intensities.

Gust factor ratios, an important parameter that allow the measurements from a specific gust duration to be converted to other gust durations of interest, are reported for various gust durations as a function of turbulence intensity.

The differences and gust factor ratios computed in this study can be applied directly to full-scale measurements, and can be used in several research areas, including analysing and homogenisation of historical wind speed time series, comparing gust climatologies of countries where different gust durations have been adopted, and so on. These factors clearly play an essential role in meteorological, climatological and wind engineering studies.
Complex eyed pockmarks associated with submarine groundwater discharge in gaseous muddy sediments, Eckernförde Bay, SW Baltic Sea
Authors: Hoffmann Jasper , Schneider von Deimling Jens , Schröder Jan , Schmidt Mark , Held Philipp , Scholten Jan , Crutchley Gareth , Gorman Andrew
Published: March 2020

Submarine groundwater discharge into coastal areas is a common global phenomenon and is rapidly gaining scientific interest due to its influence on marine biology and the coastal sedimentary environment, and it's potential as a future freshwater resource. We conducted an integrated study of hydroacoustic surveys combined with geochemical porewater and water column investigations at a well-known freshwater seep site in Eckernförde Bay (Germany).

The location and distribution of pockmarks in this area have been the focus of many studies since their discovery in 1966 including numerous investigations of their geochemical, geological and geophysical behavior. Despite several intense and extensive research campaigns (e.g. Sub-GATE/CBBL) their internal morphology and structure presented in this study were poorly constrained to date. With recent advances in shallow high-frequency multibeam echosounder methods combined with highly accurately positioned sediment cores, we can provide new insights on the influence of shallow gas and freshwater on the formation and internal morphology of the pockmarks. We show that high-frequency multibeam data can be used to detect free shallow gas in areas of enhanced freshwater advection in muddy sediments. Intra-pockmarks, forming due to ascending gas and freshwater, pose a new form of ‘eyed’ pockmarks revealed by their acoustic backscatter response. Our data suggest that in muddy sediments morphological lows combined with a strong multibeam backscatter signal can be indicative of free shallow gas and the subsequent advection of freshwater.