bluuebunny/crossref_metadata_2025 huggingface dataset:
Hemispheric Asymmetry in the Mars Summer Ionosphere at Various Solar Forcing Conditions
Authors: Pilinski Marcin , Andersson Laila , Thiemann Ed
Published: March 2020

The MAVEN satellite has now made two Martian-years of ionosphere-thermosphere (I-T) observations enabling limited studies of seasonal changes in the upper atmosphere. Before examining the ionospheric dynamics associated with space weather, we wish to understand the climatological conditions of the system.  For example, previous studies have revealed the morning electron temperature overshoot as well as a close dependence between electron temperatures and neutral densities in the equatorial regions. In this presentation, we will examine differences in the northern and southern dayside ionosphere during the summer season of each hemisphere. The differences between these two cases will be contrasted with the seasonal dependence at the equator. Differences between the equatorial and polar regions are expected due to (A) differences in neutral scale heights, (B) differences in the solar zenith angle, and (C) the equilibration of I-T coupling due to differences in solar illumination.

In this work, we present a statistical analysis of MAVEN measurements comparing the north and south summer I-T. We find that when controlling for neutral pressure and latitude, the north and south plasma densities and temperatures are nearly identical below the demagnetization altitude (higher neutral pressures). Above the demagnetization altitude (lower neutral pressures), the southern hemisphere electron densities are higher than those in the northern hemisphere by ~100%. A significantly lower electron temperature is also observed in the south at these lower pressures. Given that the difference in solar EUV (and corresponding neutral heating) is ~20% between the two summer seasons, we postulate that the significantly lower plasma densities (above the demagnetization altitude) in the northern summer are due in part to an increase in ionospheric loss. This loss may be associated with the acceleration of ionospheric particles by the draped magnetic fields at an altitude where ions are not demagnetized. Furthermore, the loss may be diminished in the southern hemisphere where crustal magnetic fields increase the standoff distance to the solar wind magnetic field.
Wildfire temperature effect on soils physical and hydraulic properties
Authors: Martínez Sofía , Contreras Cristina , Acevedo Sara , Bonilla Carlos
Published: March 2020

Wildfires affect soil physical, chemical, and hydraulic properties, which in turn control many processes such as soil water availability, soil water balance, infiltration, and soil stability. Because of the multiple factors controlling the changes in soil properties and the nature of fire events, the number of predictive models for these effects is limited. Therefore, the objective of this study was to develop a soil-burning laboratory procedure to identify changes in physical and hydraulic soil properties across a fire temperature range. With this purpose, saturated hydraulic conductivity, pH, electric conductivity, soil texture, aggregate stability, repellency, and organic matter content (OM) were measured in soils burned at increasing temperatures. Six sandy loam soils were burned at four different temperatures (300ºC, 500ºC, 700ºC and 900ºC) and non-burned samples were used as a control to compute the change on each property. Additionally, three of these soils were sampled in a naturally burned area and used later to test the laboratory setup reliability to reproduce a natural fire. Preliminary results for soils burned in a muffle furnace (300ºC for two hours) showed that the changes in physical properties are more significant with soils rich in OM. On the other hand, properties such as water retention and hydraulic conductivity curves showed little variation at 300ºC.
Identification of public crisis from typhoon cataclysm and its threshold research
Authors: Zhang Wei
Published: March 2020

With the rise of urbanization in China, the damage of natural disasters was getting worse. As one of the most important cataclysms, typhoon “Lekima”, “Hato”, “Mangkhut”, “Rammasun” effect on coastal region in China significantly. In view of contingency management, typhoon cataclysm may lead to the public crisis. This crisis accompanies particularly heavy loss and profound effect, and often associated with regional emergency capability.
How to identify the crisis from a coming tropical cyclone? When to give an early warning to decision-making department depends on the regional emergency capability? These valuable questions are remaining uncertain. 
For the purpose of answering these key questions, we research on disaster mechanism and case analysis of tropical cyclones. These researches help us to build the identification indicator of crisis and determine the threshold on society, economic, environment and Public sentiment, which are helpful for the emergency response and crisis management of tropical cyclone disaster.
Abrupt Bølling‐Allerød Warming Simulated under Gradual Forcing of the Last Deglaciation
Authors: Obase Takashi , Abe-Ouchi Ayako
Published: March 2020

During the last deglaciation, a major global warming trend was punctuated by abrupt climate changes, likely related to Atlantic meridional overturning circulation (AMOC). One problem is that an abrupt increase in the AMOC during the Bølling‐Allerød (BA) transition occurred when the melting of Northern Hemisphere ice sheets was significant, which tended to weaken the AMOC. Here, from transient simulations of the last deglaciation using an atmosphere‐ocean general circulation model, we show that an abrupt increase in the AMOC during the BA transition could occur without reduction in glacial meltwater. The abrupt increase in the AMOC accompanied abrupt warming in Greenland and sea ice retreat in the North Atlantic, consistent with proxies and previous modeling studies. The results imply that abrupt BA warming during the middle stage of the last deglaciation was a response to gradual warming under the presence of meltwater from continental ice sheets.
Spatial Distribution of Radiated Seismic Energy from Local and Regional Earthquakes in Taiwan
Authors: Mittal Himanshu , Lin Ting-Li , Huang Yun-Hsuan
Published: March 2020

The radiated energy during earthquakes is one of the important characteristics that have a great impact on human lives. The study of the released energy during earthquakes and their distribution may provide a detailed knowledge about the driving forces. The earthquakes occurring between 1994 and 2018 are used to study the spatial distribution of energy in and around Taiwan. The maximum depth of earthquakes used in the present work is 320 km. Hwang's (2012) approach based on local records from Taiwan is used to estimate energy for all earthquakes having  ML ≤ 6.4. As  ML saturates for higher magnitude earthquakes, a correction factor is applied to all earthquakes above 6.4 based on energy calculation for Chi-Chi and JiaSian earthquake. It is found that the distribution of earthquake numbers and energy is not uniform. In particular, 99% of the events occurred within 100 km while the remaining 1% occurred from 100 to 320 km. Most of the events, about 78% of the total earthquakes are confined to the upper 20 km depth. Around 90% of energy release in and around Taiwan is contributed by the earthquakes occurring to a depth of 100 km. Only a few earthquakes occur beyond 100 km depth; contributing around 10% of total released energy. The highest energy release is attributed to the eastern subduction along the Ryukyu trench. Our results show that the lower crust may play an important role in energy distribution, though most of the earthquakes have occurred in the upper crust.  So, in addition to upper crust controlling plate-driving forces, the lower crust may also control these forces causing deformation. Therefore, the temporal and spatial distributions of seismic energy release can be further studied to reveal the characteristics of the seismogenic zone in the future.

Keywords: Energy, Magnitude, Subduction, Ryukyu trench, Subduction
Effectiveness of nature at improving undergraduate performance and health
Authors: Greenhalgh Mitchell
Published: March 2020

There is a large body of research linking nature with student health and academic performance. University students are exposed to stresses due to personal and academic life challenges such that mental health services on campuses around the world are overwhelmed by the number of students that seek their services. Excessive stress prevents students from spending time outside and in nature, potentially creating a harmful feedback loop. A survey will be drafted to assess the links between time in nature, academic performance, and student health at BYU. The survey will collect information about academic performance, health, and involvement in nature from a representative random sample of BYU students. The data will be analyzed to quantify the relationships among credit-hour load, academic performance, health patterns, and time spent in nature.  This work will shed light on how universities can manage student course load and create an environment that protects student health, performance, and well-being while achieving the goals of higher education.
Pendulum MEMS gravimeters for semi-absolute gravimetry
Authors: Middlemiss Richard , Hammond Giles , Walker Richard , Prasad Abhinav
Published: March 2020

By measuring tiny variations in the Earth’s gravitational acceleration, g, one can infer density variations beneath the ground.  Since magmatic systems contain rock of differing density, changes in gravity over time can tell us when/where magma is moving. Traditional gravity sensors (gravimeters) were costly and heavy, but with the advent of the technology used to make mobile phone accelerometers (MEMS – Microelectromechanical-systems), this is changing.

At Glasgow University we have already developed the first MEMS gravity sensor and we are now working with several other European institutions to make a network of gravity sensors around Mt Etna – NEWTON-g. It will be the first multi-pixel gravity imager – enabling unprecedented resolution of Etna’s plumbing system.

While this work is ongoing, a second generation of MEMS gravity sensor is now under development. The first-generation sensor comprises a mass on a spring, which moves in response to changing values of g. This, however, can only ever be used to measure changes in gravity, which means it can be difficult to tell the difference between a geophysical signal and instrumental drift. If we could measure absolute values of gravity, then instrumental drift would become less of a concern, and we could remove the need to calibrate the sensors against commercial absolute gravimeters.

One way of making absolute measurements of gravity is to use a pendulum. This method was used for hundreds of years until the scientists and engineers essentially ran out of fabrication tolerance about 100 years ago. But now nanofabrication is at our disposal, so pendulums are a valid approach to gravimetry again. Such a gravimeter is now being designed and fabricated at the University of Glasgow. It consists of a pair of coupled pendulums, who’s oscillation period is monitored to measure gravity. Here we present the intricacies of the gravimeter design, discuss the expected performance of this new tool, and propose some implications that this sensor could have on the field of volcano gravimetry.
United States East Coast Storm Surge and Cyclone track Characteristics: Differences and Similarities for Extratropical Cyclones and Hurricanes
Authors: Booth James , Rieder Harald
Published: March 2020

Storm surge on the east coast of the United States can be generated by hurricanes or extratropical cyclones (ETCs). Understanding the differences in the impacts of these two phenomena is important for improving strategies to mitigate the damage created. As such, this work examines the magnitude, spatial footprint, and paths of hurricanes and ETCs that caused strong surge along the east coast of the US. Lagrangian cyclone track information, for hurricanes and ETCs, is used to associate surge events with individual storms. First, hurricane influence is examined using ranked surged events per site. The fraction of hurricanes among storms associated with surge decreases from 20-60% for the top 10 events to 10-30% for the top 50 events, and a clear latitudinal gradient of hurricane influence emerges for larger sets of events. Second, surge on larger spatial domains is examined by focusing on storms that cause exceedance of the probabilistic 1-year surge return level at multiple stations. Results show that if the strongest events, in terms of surge amplitude and spatial extent, are considered hurricanes are most likely to create the hazards. However, when slightly less strong events that still impact multiple areas during the storm life cycle are considered, the relative importance of hurricanes shrinks as that of ETCs grows.

Next we examine the details of the tracks of the storm events that cause strong surge events. We find that paths for ETCs causing multi-site surge at individual segments of the US east coast pass very close to the regions of impact. We find that the paths of hurricanes that cause the strongest multi-site surge are often influenced by nearby large-scale circulation patterns. We also examine the relationship between the storm surge time-evolution and the propagation speed of the low-pressure center of the storm events. For extratropical cyclones, slower moving events have weaker cyclonic winds which offsets the enhanced surge associated with the longer duration of the cyclone influence on surge. For hurricanes, there is less correlation between propagation speed and cyclonic wind motion, meaning slower moving events can still generate very strong winds. However, slow moving events still don’t cause the absolute largest events.

 
Recent and potential future evolution of practical predictability across scales
Authors: Žagar Nedjeljka , Szunyogh Istvan
Published: March 2020

In this talk we use the data from an operational ensemble prediction system to investigate recent developments in practical predictability across scales. Furthermore, we separate the estimated forecast error data into components representing the two dominant regimes in the atmosphere, the Rossby and inertia-gravity regimes. The latter is used to discuss aspects of tropical predictability.

We define the practical predictability limit of a meteorological field (e.g., meridional wind at 500 hPa) or of a variability mode (e.g., the equatorial Kelvin wave) by the forecast time at which the root mean square (rms) forecast error normalized by its saturation value reaches a prescribed threshold value (e.g., 60%).

The investigative technique fits a parametric function to the curve that describes the growth of the rms error of the forecasts with forecast time for a sample of forecasts. The parametric model describes the functional dependence of the magnitude of the forecast error on the magnitude of the initial error. Thus, it can be used for the estimation of the forecast error reduction that can be achieved by reducing the magnitude of the analysis error by a presumed percentage. Likewise, it can be used for the quantitative attribution of the forecast improvements between the years to analysis or model improvements.

The calculations are carried out for the different spatial scales and the two regimes separately.
The Basic Model Interface 2.0: A standard interface for coupling numerical models and data in the hydrologic sciences
Authors: Hutton Eric , Piper Mark , Gan Tian , Tucker Greg
Published: March 2020

The hydrologic modeling and data community has embraced the open source movement as evidenced by the ever increasing number of FAIR models and datasets available to investigators. Although this has resulted in new science through innovative model application, development, and coupling, the idiosyncratic design of many of these models and datasets acts as a speed bump that slows the time-to-science.

The Basic Model Interface version 2.0 (BMI) specification lowers this hurdle by defining a standardized interface for both models and data. This allows all models and datasets with a BMI to look alike, regardless of their underlying implementation or, in fact, even if they are truly a model or a dataset. With idiosyncratic implementation details obscured, models and data are more easily and quickly picked up and used - if you know how to use one BMI model, you know how to use any BMI model.

In addition, a common interface allows models and data to more easily be brought into a single framework in which they can be queried, run, coupled, and analyzed using a standard set of tools. The Community Surface Dynamics Modeling System (CSDMS) has developed such a modeling framework, the Python Modeling Toolkit (pymt). Although this framework was initially written for the coupling of BMI-enabled numerical models, we have extended it to include BMI-enabled datasets as well. Within such a framework, investigators are able, in a reproducible way, to: compare models to one another using a common dataset, validate models to data, ingest data into a model, swap models and data within a workflow.

As a demonstration of model-data coupling within the pymt, we present examples where BMI-enabled datasets (e.g. USGS gage data, the Operational National Hydrologic Model, NOAA’s National Water Model) are used to drive hydrologic models (e.g. FaSTMECH, PRMS).
Spontaneous dynamic rupture modeling of 2017 M 5.4 Pohang, South Korea, earthquake, using the slip-weakening friction law
Authors: Song Seok Goo , Cho Chang Soo , Ely Geoffrey
Published: March 2020

An M 5.4 earthquake occurred in the southeastern part of the Korean Peninsula in 2017. It is an oblique thrust event that occurred at a relatively shallow depth (~ 5 km) although it did not create coseismic surface rupture. A coseismic slip model was successfully obtained by inverting the ground displacement field extracted by the InSAR data (Song and Lee, 2019). In this study, we performed spontaneous dynamic rupture modeling using the slip weakening friction law. The static stress drop distribution obtained by the coseismic slip model was used as an input stress field. We adopted high performance computing (HPC) using the parallelized dynamic rupture modeling code (SORD, Support Operator Rupture Dynamics). Although our target event is moderate-sized one, we can successfully produce a spontaneous dynamic rupture model using a relatively small initial nucleation patch (radius ~ 1 km) with a relatively small slip weakening distance (~ 5 cm). Our preliminary results show that the rupture creates an asperity near the initial nucleation zone with approximately 4 MPa stress drop, then propagates obliquely upward both in the northeast and southwest directions. Although we assumed a single planar fault plane in our current rupture modeling, it seems worthwhile to dynamically model the rupture process, including complex fault geometry in following studies. Dynamic rupture modeling for a natural earthquake provides an opportunity to understand the dynamic rupture characteristics of the earthquake, including both stress drop and fracture energy.
Off-line urban building energy model reproducibility against ‘observed’ anthropogenic heat and electricity consumption
Authors: Takane Yuya , Nakajima Ko , Kikegawa Yukihiro , Sugawara Hirofumi , Ishidoya Shigeyuki , Terao Yukio , Yamaguchi Kazuki , Kaneyasu Naoki , Hara Masayuki
Published: March 2020

Here we verify an off-line urban building energy model (CM-BEM) against ‘observed’ anthropogenic heat and electricity consumption at Tokyo (Yoyogi) residential area. Anthropogenic heat (QF) due to electricity air-conditioning (AC) use (QF, AC) is estimated by continuous simultaneous observations of atmospheric O2, CO2 and turbulent CO2 and heat fluxes. Here we explain the outline of how to estimate QF, AC. (1) The O2:CO2 exchange ratio (oxidation ratio, OR) is used for the partitioning of CO2 into emissions from gas fuels and gasoline (see detail in Ishidoya et al. 2020), which allow estimating QF from gas fuels and gasoline (QF, gas and QF, traffic), respectively. (2) Total QF is estimated by turbulent heat fluxes and net radiation observations using a heat balance equation within the constant flux layer. Finally (3) the QF, AC is estimated by ‘Total QF – (QF, gas + QF, traffic)’. This estimation allows verifying directly simulated QF, AC by the CM-BEM. Our aim is an improvement of the CM-BEM to develop more realistic QF and CO2 inventory data. Here we compare simulated QF, AC, electricity consumption, and turbulent heat fluxes against observations during winter (Jan-Feb 2017) and summer (July-Aug 2018) seasons at Tokyo. Our results will be reported at the conference.

Ref.

Ishidoya et al. 2020: Consumption of atmospheric O2 in an urban area of Tokyo, Japan derived from continuous observations of O2 and CO2 concentrations and CO2 flux. Atmospheric Chemistry and Physics Discussions. under review.
Geochemical and Sr-Nd isotopic characteristics of the lamprophyre in the Tethyan Himalaya, South Tibet
Authors: Liu Zhi-Chao , Wang Jian-Gang , Liu Xiao-Chi
Published: March 2020

A lamprophyre dyke has been found in Ramba area within the Tethyan Himalaya. It intruded into the Late Triassic low-grade metasedimentary rocks (Langjiexue Group) and show typical porphyritic textures, with phlogopite as the dominant phenocrysts. In this study, we performed phlogopite 40Ar/39Ar dating and whole-rock major and trace element as well as Sr and Nd isotope geochemical analyses on the lamprophyre. The 40Ar/39Ar plateau ages (13.1 ± 0.2 Ma and 13.5 ± 0.2 Ma) of the phlogopites from two samples are both in excellent agreement with the inverse isochron ages of 13.1 ±0.3 Ma and 13.6 ± 0.3 Ma, recording the times at which the lamprophyre dyke has cooled below ~300 °C. The lamprophyre has low contents of SiO2 (51.43–55.15 wt%) and Al2O3 (11.10–11.85 wt%), high Fe2O3T (8.57–9.27 wt%) and MgO (9.14–9.49 wt %) contents with Mg# of 66–69, higher content of K2O (3.26–5.57 wt%) relative to Na2O (0.50–1.39 wt%) with K2O/Na2O of 2.3–11.1. Furthermore, the lamprophyre has high abundances of large ion lithophile elements (e.g., Rb, Ba, Sr), shows depletions in high field strength elements (e.g., Nb, Ta, Ti), and displays enrichment in light rare-earth elements over heavy rare earth elements with (La/Yb)N of 42.3~47.0. Besides, the lamprophyre is characterized by high initial 87Sr/86Sr ratios of 0.7196~0.7204 and negative εNd(t) values of -10.7~-10.8. Geochemical data suggest that the Ramba lamprophyre was likely generated by partial melting of a metasomatized, phlogopite-bearing harzburgite lithospheric mantle source, followed by crystal fractionation and varying degree of crustal assimilation. The studied lamprophyre provides a window into the composition of the subcontinental lithospheric mantle (SCLM) in the northern margin of the Indian plate. We suggest that the northern Indian plate might be involved in the Andean-type orogeny from the subduction of the Proto-Tethys Ocean during Cambrian to Early Ordovician.
What is the influence of meso-scale forcing on the ionosphere-thermosphere system?
Authors: Deng Yue
Published: March 2020

We present a systematical study crossing both data analysis and model simulation to improve the specification of the energy and momentum inputs into the ionosphere-thermosphere (IT) system, especially at meso-scale, and the system response. Our results are organized in two parts, meso-scale forcing from above and from below. First, the meso-scale forcing from magnetosphere including flow burst, electric field variability, meso-scale particle precipitation and field-aligned current (FAC) has been analyzed using both satellite and ground-based measurements. The forcing distributions are then implemented in the Global Ionosphere-Thermosphere Model (GITM) to assess the relative contributions of meso-scale forcing to the ionosphere-thermosphere (I-T) system. Secondly, the acoustic gravity waves (AGWs) trigged by the geographic events, such as hurricane and volcano, propagate from lower atmosphere to I-T and cause disturbances observable for the Global Navigation Satellite Systems (GNSS). GITM with local-grid refinement (GITM-R) has been utilized to simulate ionospheric total electron content (TEC) variations induced by those events and compared with GNSS observations. These high-resolution simulations will strongly enhance our understanding and capability to specify the meso-scale forcing for the I-T system.
Optimal coordination strategies for flood control and hydropower generation of reservoir
Authors: Zhang Lin , Ding Wei , Wang Guoli
Published: March 2020

During flood seasons, the water head of the reservoir is kept in flood limited water level (FLWL) to satisfy the flood control objective, but this runs counter to the need for hydropower generation to maintain a high water-head. This paper focuses on the optimal hedging rules by setting an appropriate FLWL to maximize the benefit of hydropower without increasing the flood damage and raise the water level at the end of flood for non-flood season/future use. Two-stage hydropower functions considering the constraint conditions which include the downstream environmental flow and installed capacity are built. On the basis of studying the marginal utilities of the two-stage hydropower functions, the competitive and collaborative relationships between flood damage and hydropower benefit were analyzed qualitatively. A two-stage reservoir operation model with two objectives that are minimum flood damage and maximum hydropower generation is developed, which considers streamflow forecast uncertainty and acceptable flood risk. The derived OHR from the model can be used to make trade-offs between flood damage and hydropower benefit under different levels of streamflow forecast uncertainty or acceptable risk. Finally, the analysis is applied to the Nierji Reservoir in the north of China. The results indicate that the OHR can increase hydropower generation 1.57x106kw·h and decrease the volume of abandoned water30.04x106m3 average annual.
Assimilation of SMAP-enhanced and SMAP/Sentinel-1A/B soil moisture data into land surface models
Authors: Kim Hyunglok , Lakshmi Venkataraman , Kumar Sujay , Kwon Yonghwan
Published: March 2020

Prediction of water-related natural disasters such as droughts, floods, wildfires, landslides, and dust outbreaks on a regional-scale can benefit from the high-spatial-resolution soil moisture (SM) data of both satellite and modeled products. The reason is that the amount of surface SM controls in the partitioning of outgoing energy fluxes into latent and sensible heat fluxes.

Recently, NASA’s SMAP mission has been implemented, in order to provide 3-km and 1-km SM data from a combination of SMAP and Sentinel-1A/B observations along with 9- and 36-km SM data retrieved from an L-band radiometer brightness temperature (TB). The 3-km and 1-km SM products were produced by combining the Sentinel-1A/B C-band radar backscatter and SMAP radiometer TB observations.

In the present study, we assimilated SMAP-enhanced (9-km) and SMAP/Sentinel-1A/B SM (3-km and 1-km) products into a land surface model (LSM): SMAP-enhanced and SMAP/Sentinel-1A/B SM data were assimilated into Noah-MP3.6 LSM. Then, these products were evaluated against ground observations in the United States. Three DA products’ error characteristics were intercompared: (1) SMAP-enhanced 9-km DA, (2) SMAP/Sentinel-1A/B 3-km DA and (3) SMAP/Sentinel-1A/B 1-km DA.

When SMAP and SMAP/Sentinel SM data sets were assimilated into LSM, the R- and ubRMSE values for 9-, 3-, and 1-km SM data were greatly improved.
Sustainability of tropical river systems in Colombia, Integrating geomorphology, hydrology and vegetation analysis in the context of global change
Authors: Pereira Masiel , Vargas Germán
Published: March 2020

Tropical rivers are fundamental elements of global hydrosphere, hydrological cycle, Earth natural systems and social system. Tropical rivers are one of the main sources of supply and availability of drinking water, generating multiple direct and indirect contributions to ecosystems and society. Anthropic pressures on tropical river systems, such as canalization, construction of lateral dams, dams, floodplain occupation, among others, generate alterations in the morphology of the channel, change sediment dynamics, and disturb ecosystems and interrelationships between them and the hydrological regimes and geomorphological units. These anthropogenic transformations can generate unpredictable changes, not linear in the medium and long term, and can become irreversible. In this light, this PhD research in Geography, analyze the relationships between geomorphology, hydrology and vegetation that occur in the middle basins of four main rivers in Colombia: Meta, Sinu, Magdalena and Cauca, assessing the vulnerability of tropical river systems in Colombia taking into account the historical relationship of human beings and rivers generating guidelines for management and sustainability of water resources in Colombia, in a context of global change, based on scientific knowledge, which allows criteria for decision-making for its management, use and conservation.
Cryospheric Applications of Novel GNSS Grazing Angle Reflections Collected by Spire CubeSats
Authors: Nguyen Vu , Yuasa Takayuki , Nogués-Correig Oleguer , Masters Dallas , Tan Linus , Duly Timothy , Sikarin Robert , Esterhuizen Stephan , Jales Philip , Freemand Vahid
Published: March 2020

Spire Global operates the world’s largest and rapidly growing constellation of CubeSats performing GNSS based science and Earth observation. Currently, the Spire constellation, with many satellites in polar orbits, performs a variety of GNSS science, including radio occultation (GNSS-RO), ionosphere and space weather measurements, and precise orbit determination. These satellites have been primarily tasked to perform GNSS-RO to produce accurate profiles of atmospheric temperature, pressure, and water vapor and to collect millions of daily ionospheric total electron content measurements. Previous work showed that grazing angle reflections of GNSS signals off of ocean and sea ice surfaces serendipitously collected during radio occultation measurements had the potential to perform precision altimetry (< 10 cm) over sea ice surfaces.

In 2019, Spire reprogrammed its STRATOS GNSS science receiver to collect grazing angle reflection observations on Spire's large constellation of orbiting GNSS-RO satellites. To accomplish this, the open-loop tracking used in GNSS-RO collection was modified to perform open-loop prediction and tracking of grazing angle reflections between 5-30 deg elevation. Initial results confirm coherency of reflections over most sea ice surfaces and some open ocean surfaces. Full altimetric processing has been performed and is being productionized, confirming  sub-10 cm precision over sea ice where reflections were coherent, with some initial measurements showing altimetric height precision less than 2 cm RMS relative a mean sea surface (e.g., DTU18). Due to the large number of current and planned GNSS-RO satellites as Spire's constellation scales to over 100 operating GNSS-RO satellites, this technique has excellent potential to complement other sensors such as ICESat-2 and Cryosat-2.

A larger production period has now begun on multiple Spire satellites that will result in much larger quantities of diverse cryospheric measurements (sea ice as well as ice sheets will be sampled). We will present further results of this new and potentially revolutionary technique to use existing orbiting GNSS-RO satellite constellations to perform precision sea ice altimetry.
A Hybrid-Precision Numerical Orbit Integration Technique for Next Generation Gravity Missions
Authors: Nie Yufeng , Shen Yunzhong , Chen Qiujie
Published: March 2020

In Next Generation Gravity Missions (NGGM) the Laser Ranging Interferometer (LRI) is applied to measure inter-satellite range rate with nanometer-level precision. Thereby the precision of numerical orbit integration must be higher or at least same as that of LRI and the currently widely-used double-precision orbit integration technique cannot meet the numerical requirements of LRI measurements. Considering quadruple-precision orbit integration arithmetic is time consuming, we propose a hybrid-precision numerical orbit integration technique, in which the double- and quadruple-precision arithmetic is employed in the increment calculation part and orbit propagation part, respectively. Since the round-off errors are not sensitive to the time-demanding increment calculation but to the least time-consuming orbit propagation, the proposed hybrid-precision numerical orbit integration technique is as efficient as the double-precision orbit integration technique, and as precise as the quadruple-precision orbit integration. By using hybrid-precision orbit integration technique, the range rate precision is easily achieved at 10-12m/s in either nominal or Encke form, and furthermore the sub-nanometer-level range precision is obtainable in the Encke form with reference orbit selected as the best-fit one. Therefore, the hybrid-precision orbit integration technique is suggested to be used in the gravity field solutions for NGGM.
Extracting Common Mode Errors of Regional GNSS Position Time Series in the Presence of Missing Data by Expectation-Maximization Principal Component Analysis
Authors: li wudong , jiang weiping
Published: March 2020

Removal of the Common Mode Error (CME) is very important for the investigation of Global Navigation Satellite Systems (GNSS) technique error and the estimation of accurate GNSS velocity field for geodynamic applications. The commonly used spatiotemporal filtering methods cannot accommodate missing data, or they have high computational complexity when dealing with incomplete data. This research presents the Expectation-Maximization Principal Component Analysis (EMPCA) to estimate and extract CME from the incomplete GNSS position time series. The EMPCA method utilizes an Expectation-Maximization iterative algorithm to search each principal subspace, which allows extracting a few eigenvectors and eigenvalues without covariance matrix and eigenvalue decomposition computation. Moreover, it could straightforwardly handle the missing data by Maximum Likelihood Estimation (MLE) at each iteration. To evaluate the performance of the EMPCA algorithm for extracting CME, 44 continuous GNSS stations located in Southern California have been selected here. Compared to previous approaches, EMPCA could achieve better performance using less computational time and exhibit slightly lower CME relative errors when more missing data exists. Since the first Principal Component (PC) extracted by EMPCA is remarkably larger than the other components, and its corresponding spatial response presents nearly uniform distribution, we only use the first PC and its eigenvector to reconstruct the CME for each station. After filtering out CME, the interstation correlation coefficients are significantly reduced from 0.46, 0.49, 0.42 to 0.18, 0.17, 0.13 for the North, East, and Up (NEU) components, respectively. The Root Mean Square (RMS) values of the residual time series and the colored noise amplitudes for the NEU components are also greatly suppressed, with an average reduction of 25.9%, 27.4%, 23.3% for the former, and 49.7%, 53.9%, and 48.9% for the latter. Moreover, the velocity estimates are more reliable and precise after removing CME, with an average uncertainty reduction of 52.3%, 57.5%, and 50.8% for the NEU components, respectively. All these results indicate that the EMPCA method is an alternative and more efficient way to extract CME from regional GNSS position time series in the presence of missing data. Further work is still required to consider the effect of formal errors on the CME extraction during the EMPCA implementation.
The StraboSpot data system for geological research
Authors: Newman Julie , Walker J. Douglas , Tikoff Basil , Williams Randolph
Published: March 2020

The StraboSpot digital data system is designed to allow researchers to digitally collect, store, and share both field and laboratory data.  Originally designed for structural geology field data, StraboSpot has been extended to field-based petrology and sedimentology.  Current efforts will integrate micrographs and data related to microscale and experimental rock deformation. The StraboSpot data system uses a graph database, rather than a relational database approach.  This approach increases its flexibility and allows the system to track geologically complex relationships. StraboSpot currently operates on two different platform types: (1) a field-based application that functions with or without internet access; and (2) a web interface (Internet-connected settings only).

 The data system uses two main concepts - spots and tags - to organize data. A spot consists of a specific area at any spatial scale of observation.  Spots are related in a purely spatial manner, and consequently, one spot can enclose multiple other spots that themselves contain spots.  Spatial data can thus be tracked from regional to microscopic scale.  Tags provide conceptual grouping of spots, allowing linkages between spots that are independent of their spatial position.  A simple example of a tag is a geologic unit or formation. Multiple tags can be assigned to any spot, and tags can be assigned throughout a field study. The advantage of tags is their flexibility, in that they can be completely defined by individual scientists. Critically, tags are independent of the spatial scale of the observation. Tags may also be used to accommodate complex and complete descriptions. 

The strength of the StraboSpot platform is its flexibility, and that it can be linked to other existing and future databases in order to integrate with digital efforts across the geological sciences.  The StraboSpot data system – in coordination with other digital data efforts – will allow researchers to conduct types of science that were previously not possible and allows geologists to join big data initiatives.
Seafloor Erosion induced by overbanking flow derived by a 2.5D high resolution sparker seismic dataset, uppermost Kaoping Submarine Canyon, southwestern offshore Taiwan
Authors: Hsiao Wei-Chung , Yeh Yi-Ching , Cho Yen-Yu , Hsu Shu-Kun
Published: March 2020

The Kaoping submarine canyon (KPSC) originates from Kaoping River, southwestern Taiwan that extends about 250 kilometers long from the Kaoping River mouth down to the Manila Trench. It can be divided into three major sections: upper reach (meandering), middle reach (NW-SE trending and V-shaped canyon) and lower reach (meandering). Based on recent a swath bathymetric data in the uppermost KPSC, an obvious seafloor depression can be observed in the eastern bank of the canyon. The eastern bank of the canyon reveals about 30-50 meters in average lower than western bank. The mechanism is blurred. In this study, to investigate fine sedimentary structures in 3D point of view, we used marine sparker seismic method. The seismic source frequency varies from 100 to 1200 Hz which can provide about 0.6 meters vertical resolution (i.e. central frequency 600 Hz and 1,600 m/s Vp). We have collected 75 in-lines across the canyon and 3 cross-lines perpendicular to the in-line. The data went through conventional marine seismic data processing procedures such as bad trace kill, band-pass filter, 2D geometry settings, NMO stacking, swell correction, match filter and predictive deconvolution. The 2D dataset was reformatted by applying 3D geometry settings to create a 3D seismic cube. The result shows that a wide incision channel was first found in the north of Xiaoliuchiu islet. Through depth, this channel becomes two narrower channels divided by a mud diapir. This down cutting can be traced down to transgressive sequence in prior to LGM (Last Glacial Maximum). In addition, a deep-towed sub-bottom profiler shows an obvious down-lapping structures heading off canyon that indicates over banking flow may be a key role to cause this erosional event.
The 2016 Mw 6.1 Petermann Ranges earthquake rupture, Australia: another “one-off” stable continental region earthquake
Authors: Quigley Mark , King Tamarah , Clark Dan
Published: March 2020

The 20th May 2016 moment magnitude (MW) 6.1 Petermann earthquake was the 2nd longest single-event historic Australian surface rupture (21 km) and largest MW on-shore earthquake in 28 years. Trench logs from two hand-dug trenches show no evidence of penultimate rupture of surface eolian sediments or underlying calcrete. Available dating of eolian dunes 140 to 500 km away from the Petermann fault indicated eolian deposition during either the last glacial maximum (approximately 20 ka) or a period of aridification at approximately 180 - 200 ka. Ten 10Be cosmogenic nuclide erosion rates of bedrock outcrops at 0 to 50 km from the surface rupture trace are within error of each other between 1.4 to 2.6 mMyr-1. These samples have approximate averaging times between 208 to 419 ka. Bedrock erosion rates, trenching results and interpretation of the landscape history suggest the 2016 event is the only surface rupturing earthquake on the Petermann fault in the last 200 to 400 kyrs, and possibly the first ever on this fault. This finding is consistent with a lack of evidence for penultimate rupture for all eleven historic Australian surface rupturing events, as described by either trenching and/or landscape analysis and bedrock erosion rates. These ‘one-off’ events within Precambrian cratonic Australian crust are not consistent with trenching results and geomorphology of paleo-scarps within the Flinders Ranges and Eastern Australia which indicate multiple recurrent fault offset. Variable fault recurrence behaviour highlights that uniform seismic hazard modelling approaches are not applicable across Stable Continental Regions.
Late Permian – Triassic Granitic Magmatism of western part of the Northern Taimyr: evidence for two magmatic events.
Authors: Kurapov Mikhail , Ershova Victoria , Khudoley Andrey , Makariev Aleksandr , Makarieva Elena
Published: March 2020

The studied intrusions are located within the Northern Taimyr domain (southern part of the Kara terrane) on the northwestern coast of the Taimyr Peninsula and on several islands in Kara Sea. Intrusions cut the Lower Paleozoic metasedimentary rocks.

Late Permian – Early Triassic intrusions are represented by coarse- to medium-grained quartz-syenites and alkali-feldspar-granites. U-Pb dating of these granites yelled age of 253 Ma. Ar-Ar micas ages varies from 236 to 251 Ma. The granites are high- to medium acidic, high alkaline (alkali-calcic to alkalic), ferroan and magnesian, mainly peraluminous. Granites are characterized by relatively low initial 87Sr/86Sr ratio (0.7041) and slightly positive εNd(t) value (1.03).

Middle – Late Triassic intrusions are represented by coarse-grained granodiorites and granites. U-Pb zircon ages of these granites range from 228 to 238 Ma. Ar-Ar micas and amphibole ages varies from 206 to 235 Ma. They are acidic to low acidic, moderately alkaline (alkali-calcic, calc-alkalic), magnesian, peraluminous and metaluminous. Middle – Late Triassic granites are characterized by higher initial 87Sr/86Sr ratios (0.7045-0.7060) and negative εNd(t) values (-5.47 to -0.80).

Late Permian – Early Triassic high alkalic predominantly ferroan granites are most likely related to A-type granites. Middle – Late Triassic moderate alkalic magnesian granites have transitional I/S-type character. Thus, Late Permian – Early Triassic granites likely form an outer rim of the Permo-Triassic Siberian plume. Middle – Late Triassic granites of Northern Taimyr were formed from different source with more significant crustal component contribution. Obtained data suggests two magmatic events throughout Early Mesozoic that affected Northern Taimyr.

This research was supported by RFBR project No. 19-35-90006
Evaluating hydrological signatures and catchment similarities to estimate model parameters in Cauvery river basin, India
Authors: Reghunath Gowri , Mujumdar Pradeep
Published: March 2020

Catchments are complex self-organizing environmental systems for which the form, drainage network, channel geometries, soil and vegetation, are all an outcome of co-evolution and adaptation to the ecological, geomorphologic and land-forming processes. Quantification of hydrological signatures provides vital information about the complex system properties and the functional behaviour of catchments. This work aims at evaluating catchment similarity with respect to geomorphology and hydrological signatures such as runoff ratio, flow duration curves and peak flows for calibrating and upscaling model parameters. The study is carried out on the sub-catchments of Cauvery river basin which is a major river basin in Peninsular India. The basin is characterized by extensive regional variability in surface and groundwater availability and large-scale shift in land use patterns in recent decades. With a significant number of anthropogenic interventions such as check dams and reservoirs, the basin faces water management challenges at the local, regional and basin scales. Hydrological signatures derived from elevation, streamflow and meteorological data are used to evaluate geomorphologic and hydrological similarity between the sub-catchments. We employ the physically based macroscale Variable Infiltration Capacity (VIC) model coupled with a routing model to simulate the streamflow. Streamflow simulations are carried out for various sub-catchments delineated based on discharge gauging stations. Model parameters are estimated and hydrological signatures are assessed for effective model calibration. Impact of interventions on flow signatures at the catchment scale is also assessed. This work can significantly improve the scientific understanding of variability of hydrological processes at various scales and provide useful insights for development of scaling relationships. It can also aid in examining the model parameter transferability across scales.
Remote sensed evidence on the control factors of grassland ecosystem response to drought in the Tibetan Plateau
Authors: Wang yijia , Fu bojie , Liu yanxu
Published: March 2020

Abstract: The Tibetan Plateau, as an ecologically fragile area with typical alpine meadow ecosystems, is sensitive to climate change, especially drought. However, spatial heterogeneity of the vegetation dynamics plays an important role in response to climate change, while there is relatively lacked evidence on their spatial control factors. Here, multivariate remote sensing data were used to construct vegetation index and multi-scale drought index to understand the vegetation dynamics and drought trend of the Tibetan plateau from 2000 to 2015, for revealing their differences or spatial response through correlation analysis. Elevation, land surface temperature, land cover and snow cover were selected as spatial control factors and the results showed that the vegetation was greening in the east while browning in the west. The vegetation indices including EVI, LAI and GPP were all closely related to drought index, while the magnitudes of response were spatially different. The contributions of control factors for the responses were not inconsistency because of the differential ecological meaning of the vegetation indices. Our results provide a spatial basis for the ecosystem management in the Tibetan Plateau by clarifying the spatial heterogeneity of control factors on the response of vegetation dynamics to drought.

Keywords: vegetation dynamics; drought response; grassland ecosystem; spatial heterogeneity; remote sensing; Tibetan Plateau