bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of the Formation of Periodic Plasma Shocks from Fast Mode Waves
Authors: Shan Lican , Du Aimin , Tsurutani Bruce , Ge Yasong , Lu Quanming , Mazelle Christian , Huang Can , Glassmeier Karl-Heinz , Henri Pierre
Published: March 2020

Collisionless plasma shocks (CPSs), forming when supersonic plasma streams encounter a magnetized obstacle, are invoked to explain the acceleration of ubiquitously energetic cosmic rays. It has long been theorized from magnetohydrodynamics, but not directly observed that the CPSs develop from the growth of small-amplitude, low-frequency plasma waves which excited by reflected ion beams from the obstacle. We present in situ observations of an entire formation sequence of the periodic plasma shocks by the MAVEN spacecraft’s magnetic field and particle instruments. The magnetometer first detected small-amplitude circularly polarized magnetosonic waves that further steepened and eventually evolved into periodic shocks. Moreover, differing from the traditional understanding, characterizations of the fast mode waves show that the free energy of the wave/shock generation is provided by newborn protons, and the increasing sunward proton fluxes provided persistent energy for wave steepening. The unusual evidence presents itself from the combination of two circumstances: radial-aligned (Sun-Mars) magnetic fields and Martian atmospheric atom (hydrogen) photoionization and solar wind pickup. These observations lead to the conclusion that newborn ions play a crucial role in the formation process of some CPSs in the astrophysical and space plasma.
High-resolution DOC measurements indicate differences in DOC mobilization processes depending on topography
Authors: Blaurock Katharina , Gilfedder Ben , Fleckenstein Jan , Peiffer Stefan , Hopp Luisa
Published: March 2020

Since the 1980s, an increase in dissolved organic carbon (DOC) concentrations in waters of the Northern hemisphere has been observed. However, no general explanation has been found so far. Our study focuses on investigating the mechanisms influencing DOC mobilization and export in the streams of a forested headwater catchment in the Bavarian Forest National Park, Germany, as controlled by topography and hydrological conditions. Our goal is to identify differences in DOC mobilization processes between steep hillslopes and riparian zones and between different precipitation events. We hypothesize that different hydrological conditions and the topographical position (steep hillslopes vs. riparian zones) influence sources of DOC and mobilization processes. 

Three continuous sampling sites were established in different topographical positions within the catchment of the Große Ohe in the Bavarian Forest National Park along one of the streams: at a steep hillslope (880 m.a.s.l.), in a transition zone where the steep hillsides level off (805 m.a.s.l.) and in a flat and wide riparian zone (770 m.a.s.l). At these three locations, DOC concentrations in stream water have been measured continuously using UV-Vis spectrometry since early summer 2018, in combination with continuous discharge measurements. In addition, we regularly conducted a longitudinal sampling in order to analyze stream water chemistry parameters at 16 sampling points along the investigated stretch of about 3 km.

We analyzed discharge and DOC dynamics and DOC-Q hysteresis patterns, derived from the high-resolution data, to investigate if DOC mobilization differed between the topographical positions. We focus on two large events with different antecedent hydrological conditions in October 2018 (Ptot: 30 mm, API14: 1.9 mm) and May 2019 (Ptot: 28.9 mm, API14: 46.8 mm). At all topographical positions, maximal DOC concentrations were higher during the event in October 2018 (up to 15 mg/l) than during the event in May 2019 (up to 10 mg/l). These maximal concentrations also persisted much longer on the falling limb of the hydrograph during the October event, following dry conditions, than during the May event, following wet conditions.  This behavior results in wider hysteresis loops at all topographical positions during the event in October 2018 than in May 2019. However, peak concentrations dropped more quickly at the site of the steep hillslope than at the site of the transition zone and the riparian zone, resulting in more compressed hysteresis loops during both events. We use these differences in the DOC-Q hysteresis patterns to identify key processes for DOC mobilization and to create a perceptual model for DOC export from small, forested catchments.
India-Asia collision paleogeography constrained by Burma Terrane (Myanmar) Late Cretaceous to Miocene paleomagnetic data
Authors: Westerweel Jan , Roperch Pierrick , Licht Alexis , Dupont-Nivet Guillaume , Win Zaw , Poblete Fernando , Cogné Nathan , Ruffet Gilles , Huang Huasheng , Swe Hnin Hnin , Thi Myat Kai , Hoorn Carina , Aung Day Wa
Published: March 2020

The paleogeographic evolution of the India-Asia collision and the resulting formation of the Himalayan orogen remain an intensely debated topic. A variety of disputed models propose different collision ages for the numerous terranes incorporated into the collision with variable paleolatitudes and tectonic rotations that can be constrained using paleomagnetism. Recent plate tectonic reconstructions have shown that the Burma Terrane (BT), a microplate at the eastern edge of the Himalayan orogen, is a key element to solve the India-Asia collision puzzle. Here we provide new paleomagnetic and geochronological data of Paleocene, Eocene, Oligocene and Miocene age, in addition to our previously published Late Cretaceous and late Eocene results. We present a robust plate tectonic reconstruction for the BT with GPlates software, and show that the BT moved towards southern hemisphere latitudes between the Late Cretaceous and Paleocene without significant rotation. Starting in the Paleocene, the BT and India coevally moved northwards and the BT started to undergo a major clockwise rotation of ~60 ̊. By the late Eocene, most of this rotation was completed and the BT was translated ~2000 km northward from near-equatorial latitudes without significant rotation. This northward translation culminated with the early Miocene indentation of the BT into the eastern Himalayan collision zone, leading to the setup of the modern Eastern Himalayan Syntaxis. These first order constraints are used to infer a Trans-Tethyan arc collision model including timing of rollback, extrusion and initiation of strike-slip systems. Our model has important implications for Asian biotic and climatic evolution.
Occurrence and altitude of the non-specular long-lived meteor trails during meteor showers at high latitudes
Authors: Kozlovsky Alexander , Lukianova Renata , Lester Mark
Published: March 2020

Meteoroids entering the Earth’s atmosphere produce ionized trails, which are detectable by radio sounding. Majority of such radar detections are the echoes from cylindrical ionized trails, which occur if the radar beam is perpendicular to the trail, i.e., the reflection is specular. Typically such echoes detected by VHF radars last less than one second. However, sometimes meteor radars (MR) observe unusually long-lived meteor echoes and these echoes are non-specular (LLNS echoes). The LLNS echoes last up to several tens of seconds and show highly variable amplitude of the radar return. The LLNS echoes are received from the non-field-aligned irregularities of ionization generated along trails of bright meteors and it is believed that key role in their generation belongs to the aerosol particles arising due to fragmentation and burning of large meteoroids. The occurrence and height distributions of LLNS are studied using MR observations at Sodankylä Geophysical Observatory (SGO, 67° 22' N, 26° 38' E, Finland) during 2008-2019. Two parameters are analyzed: the percentage and height distribution of LLNS echoes. These LLNS echoes constitute about 2% of all MR detections. However during certain meteor showers (Geminids, Perseids, Quadrantids, Arietids or/and Daytime ζ-Perseids, and Lyrids) the percentage of LLNS echoes is noticeably higher (about 6, 5, 4, 4, and 3%, respectively). Typically, the LLNSs occur ~2 km higher than other echoes (in June-July the height difference is reduced to ~1 km). Due to this elevation, a larger percentage of LLNSs is manifested as an upward shift of the height distribution of meteor trails during meteor showers. Moreover, during Lyrids, η-Aquariids, Perseids, Orionids, and Leonids the LLNS echoes occur noticeably, up to 3-6 km, higher than the echoes from other types of trails. Thus, enhanced heights of meteor detections during major meteor showers (Quadrantids, Lyrids, η-Aquariids, Arietids or/and Daytime ζ-Perseids, Perseids, Orionids, Leonids, and Geminids) are predominantly due to long-lived non-specular echoes from the non-field-aligned irregularities associated with large meteoroids.
Higher Vertical Resolution for Select Physical Processes in the Energy Exascale Earth System Model (E3SM)
Authors: Lee Hsiang-He , Bogenschutz Peter , Yamaguchi Takanobu
Published: March 2020

The low cloud bias in atmospheric models for climate and weather remains an unsolved problem. Coarse vertical resolution in the current global climate models (GCM) may be a significant cause of low cloud bias because planetary boundary layer (PBL) parameterizations, including higher-order turbulence closure (HOC), cannot resolve sharp temperature and moisture gradients often found at the top of subtropical stratocumulus layers. The aim of this work is to implement a new computational method, the Framework for Improvement by Vertical Enhancement (FIVE) into the Energy Exascale Earth System Model (E3SM) and its single column model. Three physics schemes are interfaced to vertically enhanced physics (VEP), which allows for these schemes to be computed on a higher vertical resolution grid compared to rest of the E3SM model.  In this presentation we use VEP for turbulence, microphysics, and radiation parameterizations and demonstrate better representation of subtropical boundary layer clouds while limiting additional computational cost from the increased number of levels.  We will also briefly discuss future plans for an adaptive vertical grid for VEP, which will allow for additional layers to be added only when/where they are needed.
Observing the surface radiation and energy balance, carbon dioxide and methane fluxes over the city centre of Amsterdam
Authors: Steeneveld Gert-Jan , van der Horst Sophie , Heusinkveld Bert
Published: March 2020

Cities largely affect boundary-layer climates due to complex surface structures, pollutant emissions, and anthropogenic heat release. As urban populations are expanding worldwide, insight is required into the urban surface radiation and energy balance and urban greenhouse gas fluxes. However, little long-term flux measurement records are available for dense city centres. We present one year (June 2018 - May 2019) of flux observations taken at a 40-meters tower in the city centre of Amsterdam. We analyse the diurnal and seasonal variation of the turbulent and greenhouse gas fluxes, and we estimate the flux footprint to gain insight in flux variation with wind direction. Also, anthropogenic heat flux and storage fluxes are estimated from emission inventories and the objective hysteresis model respectively. This analysis shows that, especially during the winter, the sum of the sensible and latent heat flux exceeds the net radiation. Thus, the storage flux and anthropogenic heat flux are significant energy providers. Also, we find a surprisingly good surface energy balance closure, especially during summer. To achieve annual energy closure, the sensible heat and latent heat flux require an increase of 13%. Moreover, we find that the measured carbon dioxide flux (45 kg CO2 m-2 y-1) is close to bottom-up source quantification (47 kg CO2 m-2 y-1). For some wind directions, the agreement is better than for others. In addition, we show that the annual methane emission is slightly higher than the emission found in Florence and London. Yet the methane source partitioning in Amsterdam remains open for more research.
The geodynamics of oceanic core complexes: would subduction occur at ridge-transform intersections?
Authors: Mart Yossi
Published: March 2020

Oceanic core complexes are lithological assemblages of peridotites and serpentinites, embedded in the basaltic oceanic crust at active or dormant intersections of several slow-spreading oceanic accreting rifts with fracture zones. These occurrences are presumed to derive from the upper mantle, emplaced by low-angle and large-throw normal detachment faults. The abundant serpentinites are attributed to alteration of the ultramafic peridotites during its long ascent from the upper mantle. However the absence of both high-pressure lithologies in the oceanic core complexes and the rareness of earthquakes generated by low-angle normal faulting cast doubt on the validity of this conventional model. Alternately, analog tectonic experiments showed that subduction is a probable process for the generation of oceanic core complexes, because it could develop between two juxtaposed tectonic slabs if their density contrast will exceed 200 kg/m3 with no lateral converging pressure, if the friction between the slabs were low. Indeed oceanic core complexes occur in unique oceanic domains where two basaltic slabs of contrasting densities are juxtaposed across a weakness zone of low friction. Density of fresh basalt at the accreting ridge is approximately 2700 kg/m3 and that of the older basalts, juxtaposed across the fracture zone, is ca. 2900 kg/m3. Slow spreading rates of some ridges would set slabs of significant density contrast across the fracture zone even if the transform offsets are not large. Furthermore, the thermal gradient under the ridge is some 1300/km, enabling the metamorphism of the oceanic basalts either to serpentinites or to peridotites at similar P-T constraints, depending on the availability of water. Therefore, it seems that the serpentinites are not secondary products of source-rock alteration, but genetic equivalents to the peridotites. It is presumed therefore that the pliable serpentinite would ascend diapirically through cracks in the over-riding basaltic slab and reach the seafloor, carrying along large blocks of peridotite to produce the serpentinite-peridotite petrology, that lithological association of oceanic core complexes.
A self-organizing maps methodology for developing a composite air quality and climatic parameters classification
Authors: Alimissis Anastasios , Tzanis Chris G. , Cartalis Constantinos , Philippopoulos Kostas , Koutsogiannis Ioannis
Published: March 2020

Urban climate change affects important aspects of urban life (health, urban environment and infrastructure) through considerable fluctuations in the values of both climatic and air quality parameters. At the same time, in recent years, the networks of atmospheric pollution and climatic parameters monitoring stations have become denser, leading to more information which, if presented correctly, can guide policy makers to achieve sustainable solutions. Compοsite environmental classifications are a credible tool to describe in an easily comprehensible manner the complex interactions of gaseous and particulate pollutants with climatic parameters in different land use types and urban topography. The aim of this study is the development and implementation of a composite climate - air quality classification in order to describe and study their combined effects on living conditions and quality of life in urban environments. By employing pollutant observations from surface stations and climatic gridded data from reanalysis databases, the available data will be converted into groups of cases through a process which is based on a non-linear method of clustering and categorization. An artificial neural network methodology and in particular, self-organizing maps will be used to convert non-linear statistical associations of input data into simple geometric relationships of points in a low dimensional map. This method can create classifications of air pollutants and climatic parameters that group days which follow specific patterns, hidden due to non-linear interactions. The results can contribute to finding a relationship between ambient air quality and climatic variables and subsequently gaining important knowledge in this field.
Creating a rock glacier inventory of the northern Nyainqêntanglha range (Tibetan Plateau) based on InSAR time-series analysis
Authors: Reinosch Eike , Buckel Johannes , Gerke Markus , Baade Jussi , Riedel Björn
Published: March 2020

The northern Nyainqêntanglha range on the southern Tibetan Plateau reaches an elevation of 7150 m and is mainly characterized by a periglacial landscape. A monsoonal climate, with a wet period during the summers and arid conditions during the rest of the year governs the landscape processes. Large parts of the mountain range are considered permafrost due to the high altitude and the associated low air temperature. Rock glaciers, which are bodies of ice-rich debris, are a typical landform. The recently published IPCC report on the cryospheres of high mountain areas highlights the sensitivity of rock glaciers to climate warming and emphasizes the importance of their study.

We study the distribution of rock glaciers of the northern Nyainqêntanglha range and our aim is to produce an inventory of active rock glaciers based on their surface motion characteristics. The lack of higher order vegetation and the relatively low winter precipitation enable us to employ Interferometric Synthetic Aperture Radar (InSAR) time-series techniques to study both seasonal and multi-annual surface displacement patterns. InSAR is a powerful microwave remote sensing technique, which makes it possible to study displacement from a few millimeters to centimeters and decimeters per year. It is thus suitable to detect sliding and creeping processes related to periglacial landscapes and permafrost conditions on the Earth’s surface. We use both Sentinel-1 (2015-2019) and TerraSAR-X ScanSAR data (2017-2019) for our analysis.

In this study we differentiate rock glaciers from the surrounding seasonally sliding slopes by their significantly higher surface creeping rates with mean velocities of 5–20 cm yr-1. We also observe that the velocity of rock glaciers is less dependent on the summer monsoon, which allows us to further differentiate between rock glaciers and other landforms. This method could potentially be used to create rock glacier inventories in other remote regions, as long as the snow cover in winter is thin enough to allow continuous InSAR time-series analysis. These rock glacier inventories are necessary to assess the effects of climate change on vulnerable high mountain regions.
Building Web Processing Services with Birdhouse
Authors: Ehbrecht Carsten , Kindermann Stephan , Stephens Ag , Huard David
Published: March 2020

The Web Processing Service (WPS) is an OGC interface standard to provide processing tools as Web Service.
The WPS interface standardizes the way processes and their inputs/outputs are described,
how a client can request the execution of a process, and how the output from a process is handled.

Birdhouse tools enable you to build your own customised WPS compute service
in support of remote climate data analysis.

Birdhouse offers you:

A Cookiecutter template to create your own WPS compute service.

An Ansible script to deploy a full-stack WPS service.

A Python library, Birdy, suitable for Jupyter notebooks to interact with WPS compute services.

An OWS security proxy, Twitcher, to provide access control to WPS compute services.

Birdhouse uses the PyWPS Python implementation of the Web Processing Service standard.
PyWPS is part of the OSGeo project.

The Birdhouse tools are used by several partners and projects.
A Web Processing Service will be used in the Copernicus Climate Change Service (C3S) to provide subsetting
operations on climate model data (CMIP5, CORDEX) as a service to the Climate Data Store (CDS).
The Canadian non profit organization Ouranos is using a Web Processing Service to provide climate indices
calculation to be used remotely from Jupyter notebooks.

In this session we want to show how a Web Processing Service can be used with the Freva evaluation system.
Freva plugins can be made available as processes in a Web Processing Service. These plugins can be run
using a standard WPS client from a terminal and Jupyter notebooks with remote access to the Freva system.

We want to emphasise the integrational aspects of the Birdhouse tools: supporting existing processing frameworks
to add a standardized web service for remote computation.

Links:

http://bird-house.github.io

http://pywps.org

https://www.osgeo.org/

http://climate.copernicus.eu

https://www.ouranos.ca/en

https://freva.met.fu-berlin.de/
Trace element emissions during the 2018 Kilauea Lower East Rift Zone eruption
Authors: Mason Emily , Wieser Penny , Liu Emma , Ilyinskaya Evgenia , Edmonds Marie , Whitty Rachel C W , Mather Tamsin , Elias Tamar , Nadeau Patricia Amanda , Kern Christoph , Schneider David J , Oppenheimer Clive
Published: March 2020

The 2018 eruption on the Lower East Rift Zone of Kilauea volcano, Hawai’i released unprecedented fluxes of gases (>200 kt/d SO2) and aerosol into the troposphere [1,2]. The eruption affected air quality across the island and lava flows reached the ocean, forming a halogen-rich plume as lava rapidly boiled and evaporated seawater.

We present the at-source composition – gas and size-segregated aerosol – of both the magmatic plume (emitted from ‘Fissure 8’, F8) and the lava-seawater interaction plume (ocean entry, OE), including major gas species, and major and trace elements in non-silicate aerosol. Trace metal and metalloid (TMM) emissions during the 2018 eruption were the highest recorded for Kilauea, and the magmatic ‘fingerprint’ of TMMs (X/SO2 ratios) in the 2018 plume is consistent with measurements made at the summit lava lake in 2008 [3], and with other rift and hotspot volcanoes [4,5].

We show that the OE plume composition predominantly reflects seawater composition with a small contribution from plagioclase +/- ash. However, elevated concentrations of some TMMs (Bi, Cd, Cu, Zn, Ag) with affinity for Cl-speciation in the gas phase cannot be accounted for by the silicate correction and therefore may derive from degassing of lava in the presence of elevated Cl-. In the case of silver and copper, concentrations in the OE plume are elevated above both the F8 plume and seawater.

At-vent speciation of TMMs in the F8 plume during oxidation (following a correction for ash contributions) was assessed using a Gibbs Energy Minimization algorithm (HSC chemistry, Outotec Research). We also demonstrate the sensitivity of speciation in the plume to the concentration of common ligand-forming elements, chlorine and sulfur. These results could be used as initial conditions in atmospheric reaction models to investigate how plume composition evolves as low-temperature chemistry takes over.

References:

[1] Neal C et al. (2019) Science

[2] Kern C et al. (2019) AGU Fall meeting abstract V43C-0209

[3] Mather T et al. (2012) GCA 83:292-323

[4] Zelenzki et al. (2013) Chem Geol 357:95-116

[5] Gauthier P-J et al. (2016) J Geophys 121:1610-1630
Impact of land cover on avalanche hazard: how forest cover changes affect return periods and dynamical characteristics simulated by a statistical-numerical avalanche model.
Authors: Zgheib Taline , Giacona Florie , Granet-Abisset Anne-Marie , Morin Samuel , Eckert Nicolas
Published: March 2020

Land cover and particularly forests have significant impact on snow avalanche initiation and propagation. Mountain forests can prevent avalanche initiation by stabilizing the snow in release areas, and potentially decelerate an avalanche, thus reducing runout distances. Interaction between forests and avalanches is recognized in avalanche modelling mostly by increasing friction parameters. For instance, the dry –Coulomb friction μ of the Voellmy friction law is thought to summarize snow properties, whereas the velocity-dependent friction ξ aims at representing the roughness of the path potentially related to land cover properties. In this work, we hypothesize on the temporal variability of both friction factors, inherited from their dependability on land cover, particularly the forest fraction, namely the aerial percentage of the terrain covered by forests within the extension of the avalanche path. Specifically, we show how the evolution of the forest fraction within the avalanche path affects the return period of runout distances and further dynamical characteristics of simulated avalanches. First, a Bayesian statistical-dynamical model is used to model avalanche frequency and magnitude on the selected path. The two processes are independently modelled, and the joint posterior distribution is estimated using a sequential Metropolis-Hastings algorithm. The forest-avalanche interaction is represented by increasing the total basal friction within the Voellmy friction law (TBF). Accordingly, to increase TBF, the velocity-dependent friction (turbulent friction) ξ is gradually decreased, whereas the dry –Coulomb friction μ is increased. To that end, ξ is assumed to be exponentially decaying with the forest fraction and is modelled as such. The dry –Coulomb friction μ  is assumed to be normally distributed with parameters characterizing its dependency on the release abscissa, mean release depth and the forest fraction. Then, the return period for runout distances and the whole distribution of velocities, flow depths and pressures corresponding to any return periods is computed for different forest fractions representing the true forest evolution within the studied path. Results for a typical avalanche path of the French Alps notably show that, logically, the larger the forest fraction, the higher the return period, but only for runout distances exceeding a given threshold. Future work will include the explicit calibration of the forest cover dependency within the statistical-dynamical approach.

 
Drought assessment in a changing climate with the joint deficit index
Authors: Van de Vyver Hans , Van den Bergh Joris , Van Schaeybroeck Bert
Published: March 2020

The characterization of droughts is very dependent on the time scale that is involved. To obtain an overall drought assessment, the cumulative effects of water deficits over different times need to be examined together. For instance, the joint deficit index (JDI) is based on multivariate probabilities of precipitation over various time scales from 1- to 12-months, and was constructed from empirical copulas. We examine the Gaussian copula model for the JDI, and we model the covariance across the temporal scales with a two-parameter function that is commonly used in the specific context of spatial statistics or geostatistics. The validity of the covariance models is demonstrated with long-term precipitation series.

Next, we assess the impact of climate change on future droughts, based on the JDI. We select an ensemble of CORDEX regional climate model simulations, under the emission pathways RCP4.5 and RCP8.5. The CORDEX resolution used is 0.11 degree (EUR-11). In particular, distributional changes in the JDI are analysed for the Brussels-Capital Region. This area contains climatological and synoptic stations that are operated by the Royal Meteorological Institute of Belgium, with long-term series.

 
Validation of NASA, NOAA AND ESA mid and thermal infrared data and products using the Lake Tahoe and Salton Sea automated validation sites
Authors: Hook Simon , Cawse-Nicholson Kerry , Johnson William , Radocinski Robert , Rivera Gerardo
Published: March 2020

The stated goal of NASA’s Earth Science Research Program is to utilize global measurements to understand the Earth system and its interactions as steps toward the prediction of Earth system behavior. NASA has identified the provision of well-calibrated, multiyear and multi-satellite data and product series as a key requirement for meeting this goal. In order to help address this goal we have established two automated validation sites where the necessary measurements for validating mid and thermal infrared data from spaceborne and airborne sensors are made every few minutes on a continuous basis.
The two automated validation sites are located at Lake Tahoe CA/NV and Salton Sea CA. The Lake Tahoe site was established in 1999 and the Salton Sea site was established in 2008. Lake Tahoe is ideally suited for validation of mid and thermal infrared data for several reasons including its size, homogeneity, elevation, accessibility and composition. In order to use Lake Tahoe for validation, 4 buoys have been deployed. Each buoy includes a custom-built highly accurate (50mK) radiometer measuring the surface skin temperature and several bulk temperature probes that trail behind the buoy. Each buoy includes a logging system with dial-up cellular access and two full meteorological station measuring wind speed, wind direction, relative humidity and net radiation. All the measurements are made every few minutes and downloaded hourly via a cellular modem. The buoy measurements are supplemented with a variety of atmospheric measurements made on-shore. The Salton Sea site was established in 2008 to validate high water temperatures, up to 35 C and evaluate the performance of surface temperature retrieval algorithms under wet and dry atmospheres depending on time of year. 
Data from the sites have been used to validate numerous satellite instruments including the Advanced Very High Resolution Radiometer (AVHRR) series, the Along Track Scanning Radiometer (ATSR) series, the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER), the Landsat series, the Moderate Resolution Imaging Spectroradiometer (MODIS) on both the Terra and Aqua platforms, the Visible Infrared Imaging Radiometer Suite (VIIRS) and the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS). In all cases the standard products have been validated including the standard radiance at sensor, radiance at surface, surface temperature and surface emissivity products. We will present results from the validation of the mid and thermal infrared data from several of the aforementioned instruments and cross compare those results.

© 2020 California Institute of Technology. Government sponsorship acknowledged.
Small permanent gullies: modelling and application to a semiarid region
Authors: Lima Alencar Pedro Henrique , de Araújo José Carlos , dos Santos Teixeira Adunias
Published: March 2020

Gullies are key drivers of land degradation, are important sources of sediment and increase sediment and pollutant connectivity in the catchment. They also play an important role in desertification areas, changing the water-table height and in farmlands, reducing productive areas. In this study, we attempted to model small permanent gullies, common in the Brazilian Semiarid Region, where the shallow soils limit the size of gullies cross-sections to a depth of no more than one meter. To model this process, we coupled the models of Foster and Lane (1983) and Sidorchuk (1999), in order to consider the effect of permanent gullies not considered in the first. Both models need as input the discharge peak and its duration, however, these data are frequently not available. We tested four different rain intensities (average, 60-minute, 30-minute and 15-minute), finding that the most intense 30 minutes represent the best the effects of the storms over gully erosion. The coupling of the two models is defined by a threshold that indicates when the equations for sidewall erosion proposed by Sidorchuk should be applied. To validate the model, we measured three gullies in the Brazilian Semiarid Region. The gullies were initiated in 1958 after the construction of a country road and have drainage area below 1 ha. The model yielded a Nash-Sutcliffe coefficient of 0.85.
Ultra-high resolution global warming simulations conducted with CESM
Authors: Timmermann Axel , Lee Sun-Seon , Chu Jung-Eun
Published: March 2020

To further improve our understanding of scale-interactions and key mechanisms leading to climate variability and extreme weather events, we conducted a series climate simulations using the ultrahigh-resolution Community Earth System Model (HR-CESM). The HR-CESM configuration uses a horizontal resolution of approximately 25 km for the atmospheric component and 10 km for the ocean. The simulations were carried out under present-day radiative forcing and for a variety of future greenhouse gas scenarios. This presentation highlights some key features of these simulations: the overall performance and important model biases, the representation of the Atlantic Meridional Overturning Circulation, tropical cyclone statistics, properties of sea-ice, the El Niño-Southern Oscillation, as well as their responses to future climate change. We will also present plans on how the data will be shared with the larger scientific community for further analysis and collaborative projects. 
Chemical Geodynamics of Asthenospheric Outflow in the western Pacific: Philippine Sea Back-arc Basin Mantle Source of the Yap Trench Forearc Lavas
Authors: Tang Limei , Chen Ling
Published: March 2020

We present new major and trace element chemistry and Sr, Nd, and Pb isotope data from basalts, recovered from the forearc setting of the Yap Trench in the western Pacific, and discuss their melt evolution and petrogenesis within the framework of the geodynamic interactions among the Caroline Plate, the Caroline ridge, and the Philippine Sea plate. These rocks have mid-ocean ridge basalt (MORB)-like geochemical features, including medium Fe contents, tholeiitic affinity, high TiO2 values at a given Fe2O3/MgO ratio, Ti/V, Nb/Y, Ba/Yb, and Ba/Th ratios similar to those of back-arc basin basalts (BABB), and trace element patterns commonly displayed by MORB and BABB lavas. However, these basalts are characterized by highly radiogenic Sr and Pb contents, reminiscent of western Pacific sediments. We suggest that forearc magmatism was responsible for the origin and petrogenesis of these rocks. Forearc magmatism was induced by the shrinking of the Philippine Sea plate, which squeezed out the underlying back-arc basin asthenosphere with Indian–type ambient mantle characteristics to invade the forearc mantle of the Yap Trench and causes lithospheric extension. Upwelling and decompression melting of this mantle produced MORB-like lavas in the narrow forearc setting. An apparent slab tear or gap in the subducting plate facilitate the penetration of the mantle outflow. The collision of the Caroline Ridge subducted more sediments into the mantle wedge. Melting of the subducted sediments and the invasion of the Indian-type asthenosphere into the forearc account for the highly radioactive Sr and Pb isotopes of the MORB-like lavas.
Salt tectonics in the Subalpine Chains of SE France, from rifting to Alpine shortening.
Authors: Brooke-Barnett Samuel , Csicsek Adam , Graham Rodney , Lonergan Lidia
Published: March 2020

The understanding of the evolution of salt structures in passive margins has increased significantly in recent decades, largely driven by advances in seismic reflection imaging in offshore passive margin salt basins. This has provided a new perspective with which to view analogous settings in outcrop. The Subalpine Chains of southeast France is one of these places. This region has undergone a complex tectonic history involving Early to Middle Jurassic rifting related to the opening of the Ligurian Tethys, Late Jurassic to Late Cretaceous passive margin subsidence, and Late Cretaceous to Miocene Alpine shortening. The structures and stratigraphic variations in the area strongly suggest that all of these have provided driving mechanisms for, or been associated with, halokinesis.

This study investigates the role that salt has played in the tectonic evolution of the Subalpine Chains since its deposition in the Triassic using field observations, structural cross sections and drone photography. The period of Early-Middle Jurassic rifting was associated with reactive salt rise, and halokinesis continued during the subsequent passive margin phase driven by sedimentation in the Vocontian basin. Triassic salt reached the sea bed to form salt glaciers during the Aptian-Albian when salt rise outpaced sedimentation rate.

Later, during Alpine shortening, SW directed compression was partly partitioned as sinistral strike-slip deformation along a pre-existing salt wall, forming the Rouaine-Daluis fault system. There is a discrepancy between the amounts of thin skinned shortening northwest and southeast of the strike slip system which can probably be attributed to the interplay of Jurassic Provence carbonate platform geometry, subsurface salt distribution and basement architecture. In the thin skinned domain of the Digne arc, salt diapirs and walls, formed during the rifting and passive margin phases, such as those at Chasteuil and Crête du Teillon, were tightened and displaced up the slope of the Provence Platform margin. Alpine shortening also squeezed salt to surface to form canopies such as the diapir at Gévaudan.

Halokinesis has influenced, and has been influenced by the tectonic history of the region. While previous regional shortening estimates have acknowledged the role of Triassic salt as a decollement layer, they do not account for the presence of salt walls and diapirs during Alpine shortening. Consequentially, the amount of strain in the Digne arc has likely been underestimated.
Seismic imaging of magmatic systems from the upper mantle to the surface with attenuation and scattering
Authors: De Siena Luca
Published: March 2020

Seismic tomography is the state-of-the-art technique for imaging the Earth. When applied to magmatic systems, phase-dependent imaging (e.g. travel-time tomography or noise interferometry) has shown the potential to broadly resolve magmatic anomalies. Here, I show recent advances in tomographic imaging of collisional continental structures at the upper mantle scale in SE Asia, with their influence on the distribution of magmatic systems. Then, I focus on the latest results of seismic attenuation (amplitude) tomography applied to crustal magmatic systems using both coherent waves and the stochastic signature of heterogeneities on seismic wavefields. The development of sensitivity kernels modeled using a multiple scattering description of seismic wavefields provide improved models of heterogeneous structures and better connections with alternative volcanological observations. The examples provided will span the Cascadian Arc (Mount St. Helens), Campi Flegrei caldera (Southern Italy) and Deception Island (Antarctica). Advanced imaging techniques, as full-waveform inversions and amplitude interferometry, remain biased in magmatic systems, without an improved understanding of the physics underlying anisotropy, multiple-scattering propagation and shallow-heterogeneity interaction, even if coverage substantially improves.
Preliminary hydrological polar motion excitation estimates from the GRACE Follow-On mission
Authors: Śliwińska Justyna , Wińska Małgorzata , Nastula Jolanta
Published: March 2020

Over almost 20 last years, observations from the Gravity Recovery and Climate Experiment (GRACE) mission have become invaluable as means to examine Earth global mass change. Since 2002, the relative along track motions between two identical satellites have been used to derive Earth’s time variable gravity field. The great success and scientific sound of the mission, which ended in 2017, contributed to the launch of its successor, GRACE Follow-On (GFO) in May 2018. Until now, monthly time series of GFO-based geopotential models have been made available to the users by official GRACE data centres at Center for Space Research (CSR), Jet Propulsion Laboratory (JPL) and GeoForschungsZentrum (GFZ). This data enables the continuation of many researches which started with the beginning of the GRACE mission. Such applications included monitoring of land water storage changes, drought event identification, flood prediction, ice mass loss detection, groundwater level change analysis, and more.

In geodesy, a crucial application of GRACE/GFO mission observations is the study of polar motion (PM) changes due to mass redistribution of the Earth’s surficial fluids (atmosphere, ocean, land hydrosphere). PM represents two out of five Earth Orientation Parameters (EOP), that describe the rotation of our Planet and link the terrestrial reference frame with the corresponding celestial reference frame. The use of C21, S21 coefficients of GRACE/GFO-based geopotential models is a common method for determining polar motion excitation.

In this study, we present the first estimates of hydrological polar motion excitation functions (Hydrological Angular Momentum, HAM) computed from GFO data which were provided by CSR, JPL and GFZ teams. The HAM are calculated using (1) C21, S21 coefficients of geopotential (GFO Level-2 data) as well as (2) gridded terrestrial water storage (TWS) anomalies (GFO Level-3 data). We compare and evaluate the two methods of HAM estimation and examine the compatibility between CSR, JPL and GFZ solutions. We also validate different HAM estimations using precise geodetic measurements of the pole coordinates.

Our analyses show that the highest internal agreement between different GFO solutions can be obtained when comparing CSR and JPL. Notably, GFZ estimates differ slightly from the other GFO models. The highest agreement between different GFO-based HAM, and between GFO-based HAM and reference data is obtained when GFO Level-3 data are used. We also demonstrate that the current accuracy of HAM from GRACE Follow-On mission meets the expectations and is comparable with the accuracy of HAM from GRACE Release-6 (RL06) data.
Geomorphology-based methods of generating soil thickness map in a section of Wanzhou County, Three Gorges reservoir
Authors: Xiao Ting , Yin Kunlong , Yang Beibei , Liang Xin
Published: March 2020

Soil thickness has a great importance in many processes such as slope stability, seismic local effects, landscape evolution, soil moisture distribution. It is a fundamental parameter in many environmental models. In local scale applications, direct or indirect measurements can be easily used to accurately measure soil thickness. Nevertheless, in large scale applications, it is often difficult to obtain a reliable distributed soil thickness map and existing methods have been applied only to test sites with shallow soil depth. In this research, we cope with this limitation showing a first attempt to test the applicability of some state-of-the-art soil thickness models in a test site characterized by a complex geological setting and soil thickness values extending from zero to forty meters. Two different approaches were used to derive distributed soil thickness maps: a modified version of the Geomorphologically Indexed Soil Thickness (GIST) model, purposely customized to better take into account the peculiar setting of the test site, and a regression performed with a machine learning algorithm, the Random Forest (RF), combined with the geomorphological parameters of GIST. The proposed models are implemented in a geographic information system environment on a pixel-by-pixel basis. Finally, validation quantifies errors of the two models and a comparison with geophysical data is carried out. The results showed that the GIST model is not able to fully grasp the high spatial variability of soil thickness of the study area: mean absolute error was is 10.68 m with 7.94 m standard deviation, and the frequency distribution of residuals showed a proneness to underestimation. In contrast, RF returned a better performance (mean absolute error is 3.52 m with 2.92 m standard deviation), and the derived map could be considered to be used in further analyses to feed models that require a distributed soil thickness map as a spatially distributed input parameter.
Multi-objective design of rainfall network based on information theory for streamflow simulation
Authors: Wang Wenqi , Wang Dong , Singh Vijay P. , Wang Yuankun
Published: March 2020

Rainfall networks provide rainfall data needed for water resource management and decision-making. These data are especially important for runoff simulation and forecast when intense rainfall occurs in the flood season. Rainfall networks should, therefore, be carefully designed and evaluated. Information theory-based methods have lately received significant attention for rainfall network design. This study focuses on the integrated design of a rainfall network, especially for streamflow simulation. We proposed a multi-objective rainfall network design method based on information theory and applied it to the Wei River basin in China. The rainfall network design can be viewed as the input for a rainfall-runoff model, as it was intended to consider streamflow data at the outlet hydrometric station. We use the total correlation as an indicator of information redundancy and multivariate transinformation as an indicator of information transfer. Information redundancy refers to the overlapped information between rainfall stations, and information transfer refers to the rainfall-runoff relationship. The outlet hydrometric station (Huaxian station in the Wei River basin) is used as the target station for the streamflow simulation. A non-dominated sorting genetic algorithm (NSGA-II) was used for the multi-objective optimization of the rainfall network design. We compared the proposed multi-objective design with two other methods using an artificial neural network (ANN) model. The optimized rainfall network from the proposed method led to reasonable outlet streamflow forecasts with a balance between network efficiency and streamflow simulation. Our results indicate that the multi-objective strategy provides an effective design by which the rainfall network can consider the rainfall-runoff process and benefit streamflow prediction on a catchment scale.
Evaluating drought-induced mortality risk for Robinia pseudoacacia plantations along the precipitation gradient on the Loess Plateau
Authors: Zhang Zhongdian , Huang Mingbin , Yang Yingnan , Zhao Xiaofang
Published: March 2020

Extensive afforestation with exotic species like Robinia pseudoacacia on the Chinese Loess Plateau are facing high drought-induced mortality risk due to the large fluctuations in annual precipitation and severe soil desiccation. The aim of this study was to assess the risk of drought-induced mortality for R. pseudoacacia plantations on the Loess Plateau based on plant hydraulics. We modified the routines of soil-plant-atmosphere water transfer in the Biome BioGeochemistry model (Biome-BGC) using a plant hydraulic model based on the supply-demand theory. The modified model efficiently captured the dynamics of canopy transpiration, soil moisture, leaf water potential, and regional variation in leaf area index in R. pseudoacacia stands on the Loess Plateau. We simulated the 50-year (1968-2017) plant hydraulic dynamics at 14 sites along a precipitation gradient on the Loess Plateau. The results indicated that annual average percentage loss of whole-plant hydraulic conductance (APLK) showed strong temporal variation due to climatic variability, which was positively correlated with annual potential evapotranspiration (PET) and the aridity index (the ratio of PET to annual precipitation). Along the precipitation gradient, the maximum APLK increased linearly with decreasing mean annual precipitation (MAP) and could exceed 60% at sites with MAP <446.1 mm. The sustainable growth of R. pseudoacacia plantations at these sites would face a severe threat. We analyzed the effect of soil desiccation on drought-induced mortality risk further. Soil desiccation increased the sensitivity of plant hydraulic safety to precipitation variability considerably, and the effect was more significant in areas with lower MAP. These quantitative findings should be helpful for evaluating and promoting the sustainability of plantation forests on the Loess Plateau.