bluuebunny/crossref_metadata_2025 huggingface dataset:
Can Effective Drought Index (EDI) successfully characterise meteorological drought and seasonal agricultural losses?
Authors: Mondol Md Anarul Haque , Zhu Xuan , Dunkerley David , Henley Benjamin J.
Published: March 2021

The nature and characteristics of drought are not like a flood, cyclone or storm surge since droughts cannot easily be tracked and are difficult to quantify as a distinct event. In this study, we examined the characteristics of meteorological drought occurrence and severity using the Effective Drought Index (EDI), including the drought events, drought chronology, onset and ending of drought, consecutive drought spells, drought frequency, intensity and severity, using North-Bengal of Bangladesh as a case study. The rainfall and temperature dataset of Bangladesh Meteorological Department (BMD) for the study region throughout 1979-2018 is utilised. The trends of drought are detected by using the Mann-Kendall test and Sen Slope estimation. We evaluated the performance of EDI using the Standardized Precipitation Index (SPI), historical drought records and rice production. The study finds that seasonal and annual droughts have become more frequent in all seasons except pre-monsoon. In addition, the largest decrease in seasonal EDI is found in the monsoon in both Teesta floodplain and Barind tract. In decades prior to the late 2000s, a drought spell typically started between March to May (± 15 days) and ended with the monsoonal rainfall in June/July. In the years since the last 2000s, monsoon and post-monsoon droughts spells have significantly increased. Overall, the peak intensities of droughts are higher in the Barind tract than in the Teesta floodplain, and the frequency and severity of moderate to severe drought are increasing significantly in the Barind tract. Though EDI is strongly correlated with the SPI index, EDI and rice production have a non-linear relationship and are not significantly correlated. Hence, this research suggests that there are other significant influences on yield rather than just climatological drought (e.g. irrigation, lack of technology and management etc.).
Optimization of the fault plane and coseismic slip from tide-gauge data for the 2nd May 2020 Ierapetra, Crete, Earthquake (Mw 6.6) and the associated tsunami
Authors: Baglione Enrico , Amato Alessandro , Brizuela Beatriz , Bayraktar Hafize Basak , Lorito Stefano , Piatanesi Alessio , Romano Fabrizio , Tonini Roberto , Volpe Manuela , Basili Roberto
Published: March 2021

We present a tsunami source solution for the 2nd May 2020, Mw 6.6 earthquake that occurred about 80 km offshore south of Crete on the shallow portion of the Hellenic Arc Subduction Zone (HASZ). This earthquake generated a small local tsunami recorded by the Ierapetra tide gauge on Crete island's southern coast. We used these single-marigram data to constrain the main features of the causative rupture. We modelled synthetic tsunami waveforms and measured their misfits with the observed data for each set of source parameters, scanned systematically around the values constrained by some of the available moment tensors.

In the attempts to discriminate between the two auxiliary fault planes of the moment tensor solutions, our results identify a shallow highly-dipping back-thrust fault as the source of this earthquake with the lower misfit. However, a rupture on a lower angle fault, possibly a splay fault of the subduction interface, with a sinistral component due to the oblique convergence on this segment of the HASZ, cannot be ruled out.

These results are relevant in the framework of the tsunami hazard assessments and Tsunami Early Warning Systems. In these frameworks, in addition to the subduction interface and possible ruptures on splay faults, other rupture types, such as those on secondary structures of the considered subduction system, cannot be excluded a priori. This circumstance bears important consequences because, as well as splay faulting, back thrust faulting might enhance the tsunamigenic potential where the subduction itself is less tsunamigenic due to the oblique convergence.
An Uncertainty Estimation Framework to Quantify the Water Balance of Ethiopian Rift Valley Lake basin
Authors: Abraham Tesfalem , Liu Yan , Tekleab Sirak , Hartmann Andreas
Published: March 2021

In Ethiopia, more than 80% of big freshwater lakes are located in the Rift Valley Lake Basin, which is serving for multipurpose water use of over 30 million people. The basin is one of the most densely populated regions in Ethiopia and it covers an area of 53,035 km2. However, most of the catchments recharging these lakes are ungauged and their water balance is not well quantified, and hence, limiting the development of appropriate water resource management strategies. Prediction for ungauged catchments has demonstrated its effectiveness in hydro-climatic data-rich regions. However, these approaches are not well evaluated in the climatic data-limited condition and the consecutive uncertainty emerging in the small catchments is not adequately quantified. In this study, we use the HBV model to simulate streamflow using global precipitation and potential evapotranspiration products as forcings. We develop and apply a Monte-Carlo scheme to calibrate the model and quantify uncertainty at 16 catchments in the basin where gauging stations are available. Out of these, we use 14 best catchments to derive the best regional regression model by correlating the best calibration parameters, the best validation parameters, and parameters that give the most stable predictions with catchment attributes that are available throughout the basin. A weighting scheme in the regional regression accounts for parameter uncertainty in the calibration. A spatial cross-valuation that is applied 14 times always leaving out one of the gauged catchments provides 14 regional regression functions that express uncertainty regionalization. It also shows that the regionalization procedure that uses the best validation parameters for regionalization provides the most robust results. We then subsequently apply the 14 spatial regression functions of the cross-validation to the remaining 35 ungauged catchments in the Rift Valley Lake Basin to provide regional water balance estimations including quantification of regionalization uncertainty. With these results, our study provides a new procedure to use global precipitation and evapotranspiration products to predict and evaluate streamflow simulation for hydro-climatically data scares regions considering uncertainty. It, therefore, enhances the confidence in the understanding of water balance in those regions and will support the planning and development of appropriate water resource management strategies.

 

Keywords: Parameters Estimation, Uncertainties, Ungauged Catchment, Weighted Regression, Water Balance
Spectral Analysis of Individual Terrestrial Gamma-ray Flashes Detected by ASIM
Authors: Lindanger Anders , Marisaldi Martino , Sarria David , Østgaard Nikolai , Lehtinen Nikolai , Mezentsev Andrey , Kochkin Pavlo , Skeie Chris Alexander , Ullaland Kjetil , Yang Shiming , Genov Georgi , Carlson Brant , Neubert Torstein , Reglero Victor , Christiansen Freddy , Köhn Christoph , Maiorana Carolina , Bjørge-Engeland Ingrid
Published: March 2021

Terrestrial Gamma-ray Flashes (TGFs) are sub-millisecond bursts of high-energy photons associated with lightning flashes in thunderstorms. The Atmosphere-Space Interactions Monitor (ASIM), launched in April 2018, is the first space mission specifically designed to detect TGFs. We will mainly focus on data from the High Energy Detector (HED) which is sensitive to photons with energies from 300 keV to > 30 MeV, and include data from the Low Energy Detector (LED) sensitive in 50 keV to 370 keV energy range. Both HED and LED are part of the Modular X- and Gamma-ray Sensor (MXGS) of ASIM.

The energy spectrum of TGFs, together with Monte Carlo simulations, can provide information on the production altitude and beaming geometry of TGFs. Constraints have already been set on the production altitude and beaming geometry using other spacecraft and radio measurements. Some of these studies are based on cumulative spectra of a large number of TGFs (e.g. [1]), which smooth out individual variability. The spectral analysis of individual TGFs has been carried out up to now for Fermi TGFs only, showing spectral diversity [2]. Crucial key factors for individual TGF spectral analysis are a large number of counts, an energy range extended to several tens of MeV, a good energy calibration as well as knowledge and control of any instrumental effects affecting the measurements.

Thanks to ASIM’s large effective area and low orbital altitude, single TGFs detected by ASIM have much more count statistics than observations from other spacecraft capable of detecting TGFs. By comparing Monte Carlo simulations to the energy spectrum from single ASIM TGFs we will aim to put stricter constraints on the production altitude and beaming geometry of TGFs. We will present the dataset, method, and some results of the spectral analysis of individual TGFs.

References:

1. Dwyer, J. R., and D. M. Smith (2005), A comparison between Monte Carlo simulations of runaway breakdown and terrestrial gamma-ray flash observations, Geophys. Res. Lett., 32, L22804, doi:10.1029/2005GL023848.

2. Mailyan et al. (2016), The spectroscopy of individual terrestrial gamma-ray flashes: Constraining the source properties, J. Geophys. Res. Space Physics, 121, 11,346–11,363, doi:10.1002/2016JA022702.
Uncertainties on plastic concentration estimates at sea
Authors: Mercier Matthieu , Poulain-Zarcos Marie , ter Halle Alexandra , Saint-Martin Marion , Simatos Florian
Published: March 2021

The large difference between the estimates of global plastic input in mass in the oceans (Jambeck et al., Science 347, 2015) and current global predictions from numerical models (van Sebille et al., Environ. Res. Lett. 10, 2015) or observations (Cózar et al., P. Natl. Acad. Sci., 111, 2014) is one of the most important issue regarding oceanic plastic litter. Yet, global predictions are based on observations, and uncertainties on the latter are rarely considered to provide error bounds on the former.

We discuss here the sources of uncertainties on plastic concentrations estimates (in number and mass), based on a recent model presented in (Poulain et al., Environ. Sci. Technol. 53, 2019). The two main sources of error are the plastic rise velocity and the model for the turbulent diffusivity, although they do not have the same importance. We validated the model with controlled laboratory experiments. Applying this model to global predictions provides us with more realistic encompassing values for the mass of plastic at sea, with a more important correction concerning small microplastics (with characteristic dimensions smaller than ~1mm).
Benchmarking GPS stations: an improved way to identify the GPS sensitivity
Authors: Klos Anna , Kusche Jürgen , Lenczuk Artur , Leszczuk Grzegorz , Bogusz Janusz
Published: March 2021

Global Positioning System (GPS) stations are affected by a plethora of real and system-related signals and errors that occur at various temporal and spatial resolutions. Geophysical changes related to mass redistribution within the Earth system, common mode components, instability of GPS monuments or thermal expansion of ground, all contribute to the GPS-derived displacement time series. Different spatial resolutions that real and system-related errors occur within are covered thanks to the global networks of GPS stations, characterized presently by an unprecedented spatial density. Various temporal resolutions are covered by displacement time series which span even 25 years now, as estimated for the very first stations established. However, since the GPS sensitivity remains unrecognized, retrieving one signal from this wide range of processes may be very uncertain. Up to now, a comparison between GPS-observed displacement time series and displacements predicted by a set of models, as e.g. environmental loading models, was used to demonstrate the accuracy of the model to predict the observed phenomena. Such a comparison is, however, dependent on the accuracy of models and also on the sensitivity of individual GPS stations. We present a new way to identify the GPS sensitivity, which is based on benchmarking of individual GPS stations using statistical clustering approaches. We focus on regional sets of GPS stations located in Europe, where technique-related signals cover real geophysical changes for many GPS permanent stations and those located in South America and Asia, where hydrological and atmospheric loadings dominate other effects. We prove that combining GPS stations into smaller sets improves our understanding of real and system-related signals and errors.
Remote sensing characterization of transitional to alkaline igneous rocks and their potential mineralizations using ASTER data: the Moroccan Central High Atlas case study
Authors: Ahechach Youssef , Ouabid Muhammad , Raji Otmane , Bodinier Jean-Louis , Amrouch Khalid , Ouali Houssa , Soulaimani Abderrahmane
Published: March 2021

Alkaline complexes are an important target for geological exploration, with both scientific and economic interests. They are host to different types of mineral deposits, such as Rare Earths, igneous phosphates, -and K-rich minerals and rocks. In Morocco, the Central High-Atlas (CHA) hosts several transitional to alkaline complexes ranging from Upper Jurassic to Eocene and showing almost all the differentiation terms of transitional to alkaline suites. These alkaline complexes are however poorly explored and their potential in terms of mineral resources is still elusive.

The aim of this research is to use Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to discriminate different transitional to alkaline rock lithologies and their associated mineralizations. For that purpose, series of band ratios proven to be sensitive to the silica, mafic, felsic and carbonate contents of transitional to alkaline rocks were applied. Our results show that the major Upper Jurassic magmatic intrusions of Moroccan CHA, such as Anemzi, Inouzane, Tassent, and Tasraft, hold distinct igneous facies, mainly composed of Mafic to felsic rocks. Field and petrographic observations have confirmed the ASTER results and highlighted that these rocks are formed of gabbro to syenite. The later are associated with significant feldspar concentrations, but also host apatite, garnet, and magnetite vein-type ores. Thereafter, field- and petrographic-based data were used as training data to perform a supervised classification allowing to refine the geological mapping of the studied alkaline intrusions.
Ground-level atmospheric electricity of mid-latitude Nimbostratus and Stratus cloud at Swider station, Poland
Authors: Odzimek Anna , Baranski Piotr , Kubicki Marek , Berlinski Jerzy , Jasinkiewicz Danuta
Published: March 2021

We present main results of our analysis of the ground-level atmospheric electricity under  Nimbostratus and Stratus clouds at mid-latitude Geophysical Observatory in Swider. Atmospheric electricity data from the Geophysical Observatory in Swider was analysed according to the calculation scheme allowing to obtain the main components of the current density in such conditions, i.e. conduction current density and precipitation or convection current, based on the basic measured parameters: electric field, Maxwell current density and total air conductivity. The atmospheric electric field and conduction current is more likely downward under Stratus cloud as is the precipitation or convection current. The electric field under Nimbostratus during snow at the ground is downward and during rain is upward and sometimes also upward precipitation current occurs during heavier rain. Mean values of electric field, conductivity, conduction and precipitation current have been obtained and an average mean current budget was calculated. Another analysis concerns the dependence of precipitation current density on the electric field at the Earth's surface in the conditions of Nimbostratus with continuous, stable precipitation, in historical cases reported as linear. The dependence of the linear regression coefficients on the value of electrical conductivity of the air was particularly investigated from the angle of the theoretical results of the work of Ette and Oladiran (1980).
First measurements of 222Rn and 220Rn activities in soil in Taylor Valley, Antarctica.
Authors: Ruggiero Livio , Sciarra Alessandra , Galli Gianfranco , Mazzini Adriano , Mazzoli Claudio , Tartarello Maria Chiara , Florindo Fabio , Wilson Gary , Bigi Sabina , Sassi Raffaele , Anderson Jacob , Ciotoli Giancarlo
Published: March 2021

Warming global climate threatens the stability of the polar regions and may result in cascading broad impacts. Studies conducted on permafrost in the Arctic regions indicate that these areas may store almost twice the carbon currently present in the atmosphere. Therefore, permafrost thawing has the potential to magnify the warming effect by doubling the more direct anthropogenic impact from burning of fossil fuels, agriculture and changes in land use. . Permafrost thawing may also intensify the Rn transport due to the increase of fluid saturation and permeability of the soil. A detailed study of 222Rn and 220Rn activity levels in polar soils constitutes a starting point to investigate gas migration processes as a function of the thawing permafrost. Although several studies have been carried out in the Arctic regions, there is little data available from the Southern Hemisphere. The Italian – New Zealand “SENECA” project aims to fill this gap and to provide the first evaluations of gas concentrations and emissions from permafrost and/or thawed shallow strata of the Taylor Valley, Antarctica. Taylor Valley is one of the few Antarctic regions that are not covered by ice and therefore is an ideal target for permafrost investigations. Results from our first field observations highlight very low values for 222Rn (mean 621 Bq m-3, max value 1,837 Bq m-3) and higher values for 220Rn (mean 11,270 Bq m-3, max value 27,589 Bq m-3), suggesting a shallow source. These measured activity values are essentially controlled by the radionuclide content in the soil, by the permeability and porosity of the soil, and by the water content. This dataset also represents an important benchmark for future measurements to track the melt progress of Antarctic permafrost.
Estimation of aboveground plant water storage using Sentinel-2 images in a semi-arid area
Authors: Liu Liang , Li Shaoda , Luo Xinrui , Yang Wunian , Zhang Yuhang , Lei Junjie , Chen Guo , Tang Xiaolu
Published: March 2021

Aboveground plant water storage (APWS), the total of water storing in aboveground parts of plant, has the function of sustaining the balance between water loss by transpiration and water gain of root uptake. APWS is also essential for plants and hydrological cycle, particularly for semi-arid areas, where water availability is limited. However, APWS varies spatially due to the heterogeneity of natural areas that are composed of a large variety of vegetation types, and studies on the spatial variability of APWS are quite limited in semi-arid areas. To fill this knowledge gap, we established 55 inventory plots with 36 plots in forests and 19 plots in shrubs to detect the spatial variability of APWS using a Random Forest (RF) algorithm and Sentinel-2 images in Mao County, China. Field observations indicated that APWS varied significantly with ecosystems, with the highest APWS in forests. Regardless of ecosystem type, mean APWS in Mao Country was 117.63 Mg ha-1. 10-fold cross-validation suggested that the RF model could reasonably predict APWS (model efficiency = 0.68, root mean square error = 54 Mg ha-1), enabling to capture the spatial variability of APWS. A robust spatial variability of APWS was observed with the highest APWS in forests located high altitude areas, while the lowest APWS was found in shrubs located in low altitude areas. Total APWS was 3.39×107 Mg across the whole study area, which could be used as a valuable natural resource for the semi-arid area. Our study successfully explored the spatial variability of APWS, suggesting the capability of detecting APWS using Sentinel-2 and providing essential data evidence for environmental protection for semi-arid areas.
Volcanic Tremor and its Relation to Volcano- and Glacier-related Processes
Authors: Eibl Eva P. S.
Published: March 2021

Volcanic eruptions can affect the climate system, the environment and society. On ice covered volcanoes this threat intensifies due to the increasing explosivity in contact with water. Monitoring and early-warning of such eruptions is closely linked to real-time, multidisciplinary data analysis. This builds on a good understanding and location of the recorded signals.

I will summarize my work on understanding and modelling volcanic tremor, a long-lasting seismic signal with emergent onset. This tremor accompanies various volcano- and glacier-related processes and has to be reliably detected and distinguished from other sources. My examples range from modelling pre-eruptive subglacial tremor and silent magma flow, to monitoring eruptive tremor, to early warning of subglacial flooding, to hydrothermal explosions and boiling and other sources such as helicopters. These results are based on array analysis, amplitude location techniques and single-station arrays but I will also risk a look into the future embracing the emerging field of rotational seismology which might solve some challenges we face in volcanic and glacial environments and advance our understanding and modelling of volcanic signals at remote sites.
Eigen-glaciers: elucidating hidden features in the flow of Sermeq Kujalleq (Jakobshavn Glacier), Greenland.
Authors: Ashmore David , Mair Douglas , Higham Jonathan , Brough Stephen , Lea James , Nias Isabel
Published: March 2021

The increasing volume and spatio-temporal resolution of satellite-derived ice velocity data has created new exploratory opportunities for the quantitative analysis of glacier dynamics. One potential technique, Proper Orthogonal Decomposition (POD), also known as Empirical Orthogonal Functions, has proven to be a powerful and flexible technique for revealing coherent structures in a wide variety of environmental flows: mapping hydraulic vortex shedding patterns, the dynamics of fluidised granular beds, and the magnetohydrodynamics of sunspots.

POD exactly describes a series of snapshots from a flow field with the product of ranked spatially orthogonal Eigenfunctions, or “modes” of spatial weighting, and one-dimensional “temporal” coefficients (Eigenvectors). In many cases the variance of the flow field is well described by just a few dominant modes. The orthogonal nature of each mode, by definition, means that the relative contribution of independent forcing mechanisms on the flow can, in theory, be separated.

In this study we investigate the applicability of POD to freely available TanDEM-X/TerraSAR-X derived ice velocity datasets of Sermeq Kujalleq (Jakobshavn Glacier), Greenland. We outline the POD procedure using the singular value decomposition of a rearranged and resampled velocity matrix and investigate the factors responsible for the dominant modes. We find dominant modes interpreted as relating to the stress-reconfiguration at the glacier terminus and the development of the glacier hydrological system, but also find that the POD is sensitive to data resampling and quality. With the proliferation of publicly available optical and radar derived velocity products (e.g. MEaSUREs/ESA CCI) we suggest POD, and potentially other modal decomposition techniques, will become increasingly useful in future studies of ice dynamics.
GCM Model Selection Procedure for Downscaling
Authors: Pickler Carolyne , Mölg Thomas
Published: March 2021

Downscaling has been widely used in studies of regional and/or local climate as it yields greater spatial resolution than general circulation models (GCM) can provide.  It can approached in two distinct ways: 1) Statistical and 2) Dynamical.  Statistical downscaling utilizes mathematical relationships between large-scale and regional/local climate to transform GCM or reanalysis data to a higher spatial resolution.  Dynamical downscaling comprises forcing the lateral boundaries of a regional climate model with reanalysis or GCM data.  However, there is no set technique to select said GCM(s).

A comprehensive yet easily applicable selection procedure was created to address this.  Using reanalysis data and/or observational data, the space-time climatic anomalies and the mean state of the climate are evaluated for the region of interest.  East Africa was utilized as a case study and GISS-E2-H r6i1p3 was found to perform the strongest.  This procedure cannot, however, tell whether the models can reproduce the key processes of the region.  To examine this, the ability of the models to simulate the Indian Ocean Dipole were evaluated.  It was found that higher ranked models were better able to capture it than lower ranked ones.  Furthermore, to ensure that a higher ranked model yielded a better downscaling simulation, three 10-year regional climate model simulations over East Africa were undertaken, where they were respectively forced by the highest ranked GCM (GISS-E2-H r6i1p3), the lowest ranked GCM (IPSL-CM5A-LR r4i1p1) and the MERRA-2 reanalysis product.  The simulated surface temperature and precipitation for Equatorial East Africa were compared with a gridded observational dataset (CRU TS 4.04).  Results showed that the higher ranked GCM produced a better downscaled simulation than the lower ranked one, a result that was more evident for surface temperature than precipitation.
An Evolving Understanding of Enigmatic Large Ripples on Mars
Authors: Lapotre Mathieu , Ewing Ryan , Lamb Michael
Published: March 2021

Unlike terrestrial sandy deserts, Mars hosts two scales of ripples in fine sand. Larger, meter-scale ripples are morphologically distinct from small, decimeter-scale ripples, and their size, in particular, decreases with increasing atmospheric density. As a result, it was recently proposed that the equilibrium size of the larger ripples is set by an aerodynamic process, which makes them larger under thinner atmospheres. Under this hypothesis, large martian ripples would be distinct from smaller, decimeter-scale impact ripples in a mechanistic sense. Several workers have followed up on these initial observations to either corroborate, counter, or expand upon that hypothesis. Notably, a mechanistic model that not only corroborates the hypothesis that the size of large martian ripples is set by an aerodynamic process but also suggests that they arise from an aerodynamic instability, distinct from the grain-impact instability thought to be responsible for the formation of impact ripples, was developed. Conversely, other workers proposed that large ripples can develop from small impact ripples in a numerical model due to Mars’ low atmospheric pressure. In the latter model, the ripples’ growth-limiting mechanism is consistent with an aerodynamic process, but the large ripples would not be a separate class of ripples – they would simply be a larger version of the small impact ripples. Here, we explore this debate by synthesizing recent advances in large-ripple formation and offer potential avenues to address outstanding questions. Although significant knowledge gaps remain, it is clear that large martian ripples are larger where the atmosphere is less dense. The size of large martian ripples thus remain a powerful paleoclimate indicator.
Magnetospheric Response to Solar Wind Forcing: ULF Waves – Particle interaction Perspective 
Authors: Zong Qiugang
Published: March 2021

Solar wind forcing, e.g. interplanetary shock and/or solar wind dynamic pressure pulses impact on the Earth’s magnetosphere manifests many fundamental important space physics phenomena including producing electromagnetic waves, plasma heating and energetic particle acceleration. This paper summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma physic based on in situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations.

Magnetosphere response to solar wind forcing, is not just “one-kick” scenario. It is found that after the impact of solar wind forcing on the Earth’s magnetosphere, plasma heating and energetic particle acceleration started nearly immediately and could last for a few hours. Even a small dynamic pressure change of interplanetary shock or solar wind pressure pulse can play a non-negligible role in magnetospheric physics. The impact leads to generate series kind of waves including poloidal mode ultra-low frequency (ULF) waves. The fast acceleration of energetic electrons in the radiation belt and energetic ions in the ring current region response to the impact usually contain two contributing steps: (1) the initial adiabatic acceleration due to the magnetospheric compression; (2) followed by the wave-particle resonant acceleration dominated by global or localized poloidal ULF waves excited at various L-shells.

Generalized theory of drift and drift-bounce resonance with growth or decay localized ULF waves have been developed to explain in situ spacecraft observations. The wave related observational features like distorted energy spectrum, boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the frame work of this generalized theory. It is worthy to point out here that poloidal ULF wave is much more efficient to accelerate and modulate electrons (fundamental mode) in the radiation belt and charged ions (second harmonic) in the ring current region. The results presented in this paper can be widely used in solar wind interacting with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.
Japan's L-SAR missions
Authors: Sobue Shin-ich , Tadono Takeo , Miura Satoko , Noda Akiko , Motooka Takeshi , Ohki Masato
Published: March 2021

Japan Aerospace Exploration Agency (JAXA) launched its first L-band SAR mission - Japanese Earth Resources Satellite (JERS-1) in 1992. Though the design life of JERS-1 was 2 years, the satellite had obtained observational data for more than 6 years and ended the mission in 1998. Following to JERS-1, Advanced Land Observing Satellite (ALOS) was launched in 2006. ALOS was equipped with three sensors: the Phased Array type L-band SAR (PALSAR), the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), and the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2). ALOS's observation data has been used in various areas including disaster mitigation through observing regions damaged by earthquakes, tsunami, or typhoons, as well as carrying out forest monitoring, natural environment maintenance, agriculture, and compiling a 1/25,000 topographical map. When the Great East Japan Earthquake hit Japan in 2011, ALOS took some 400 images over disaster-stricken areas to provide information to all parties concerned.

Technologies acquired from the ALOS are succeeded to the second Advanced Land Observing Satellite “ALOS-2.”, which was successfully launched on 24th May 2014. The mission sensor of ALOS-2 is the Phased Array type L-band Synthetic Aperture Radar-2 called PALSAR-2 which is the state-of-the-art L-band SAR system. Until now after the successful completion of initial checkout after launching, ALOS-2 has been contributed to a lot of emergency observations for natural disasters, not only in Japan but also in the world. Furthermore, based on the Basic Observation Scenario (BOS) of ALOS-2, 10m global map data and other mode data are routinely collected and archived. This paper describes the results of ALOS-2 operation in nominal operation phase and outline of future ALOS series missions, especially ALOS-4 launched JFY2022.
On the inertial instability of the Kolmogorov flow in a rotating stratified fluid
Authors: Kurgansky Michael
Published: March 2021

The linear and non-linear inertial stability of the Kolmogorov flow in a rotating viscous fluid of uniform density is investigated. A necessary condition for instability is the violation of the criterion of non-viscous inertial stability, and the sufficient condition of instability is formulated in terms of the Reynolds criterion. The existence of stable secondary stationary regimes in the problem is shown, developing in a context of loss of stability of the main flow and having the shape of rolls (cloud streets in the atmosphere) oriented along it. Stable density stratification is taken into account when the direction of gravity coincides with the direction of rotation of the fluid. In this case, the necessary condition for the inertial instability of the main flow remains the same, but the critical Reynolds number for the instability depends on two additional dimensionless parameters that appear in the problem: the stratification parameter and the Prandtl number. The case of Prandtl numbers less than or equal to unity has been studied in greater detail, when there is a secondary stationary regime, which can be unstable - in contrast to the case of a fluid that is uniform in density - and density stratification is a destabilizing factor.
A multidisciplinary study for geothermal energy sources identification in the Baia Mare area (Romania)
Authors: Panea Ionelia , Gaina Carmen , Mocanu Victor , Munteanu Ioan , Petrescu Lucian , Matenco Liviu , Scradeanu Daniel , Tuluca Florina , Scradeanu Mihaela , Nache Florin , Zlibut Alexandru , Bouaru Catalin-Florin , Minakov Alexander , Magni Valentina
Published: March 2021

Geothermal energy is known as a renewable source that has little effect on environment, since no burning process is involved in the producing of thermal and electric energy. Geothermal water is considered an environmentally friendly energy source which is valuable especially in polluted areas. Our study area, the Baia Mare region, is located in the northwestern part of Romania, a region known as one of the most polluted environment in Romania due to its long-lasting local mining and metallurgical activities. Additional quantities of CO2 emissions resulted from the use of various, relatively cheap, heating sources by the local population. The main goals of our study are to evaluate the subsurface geothermal potential of the Baia Mare area and to identify promising geothermal exploitation sites. Heat flow values in this area are among the highest in Romania. We therefore plan to combine geological, geophysical, geochemical and hydrogeological data (geo-data) in order to provide a geoscientific solution for increasing the geothermal energy production in this part of Romania. Our research program contains surface geological mapping, geophysical surveys (active and passive seismic, magnetic, magnetotelluric and geothermal), geochemical analysis, hydrogeological surveys, modeling of geo-data and joint interpretation of geo-data. An initial 3D geothermal model will be built using existent geo-data. This model will help us to identify subsurface structures which show high potential for geothermal exploration. Interpretation of existent active seismic data collected during previous hydrocarbon exploration will provide information about the subsurface structural geology. The results of the new interpretation will be compared and correlated with the existent geological maps and sections for the study area. The magnetic data available in the public domain will be used to identify subsurface igneous bodies. The temperature data available from previous measurements will be used to build temperature-versus-depth distributions. These results will be analysed within a larger geodynamic framework. A pilot site will be selected after the analysis of the initial 3D geothermal model on which we plan to collect and record new geo-data. Data processing, inversion and modeling will be performed in order to create the final geothermal model with locations of promising exploitation wells. 
Assessing local and spatial uncertainty with HER method
Authors: Thiesen Stephanie , Ehret Uwe
Published: March 2021

Uncertainty analysis is a critical subject for many environmental studies. We have previously combined statistical learning and Information Theory in a geostatistical framework for overcoming parameterization with functions and uncertainty trade-offs present in many traditional interpolators (Thiesen et al. 2020). The so-called Histogram via entropy reduction (HER) relaxes normality assumptions, avoiding the risk of adding information not available in the data. The authors showed that, by construction, the method provides a proper framework for uncertainty estimation which accounts for both spatial configuration and data values, while allowing one to introduce or infer properties of the field through the aggregation method. In this study, we explore HER method in the light of uncertainty analysis. In general, uncertainty at any particular unsampled location (local uncertainty) is frequently assessed by nonlinear interpolators such as indicator and multi-gaussian kriging. HER has shown to be a unique approach for dealing with uncertainty estimation in a fine resolution without the need of modeling multiple indicator semivariograms, order-relation violations, interpolation/extrapolation of conditional cumulative distribution functions, or stronger hypotheses of data distribution. In this work, this nonparametric geostatistical framework is adapted to address local and spatial uncertainty in the context of risk mapping. We investigate HER for handling estimations of threshold-exceeding probabilities to map the risk of soil contamination by lead in the well-known dataset of the region of Swiss Jura. Finally, HER method is extended to assess spatial uncertainty (uncertainty when several locations are considered together) through sequential simulation. Its results are compared to indicator kriging and benchmark models available in the literature generated for this particular dataset.

Thiesen S, Vieira DM, Mälicke M, Loritz R, Wellmann JF, Ehret U (2020) Histogram via entropy reduction (HER): an information-theoretic alternative for geostatistics. Hydrol Earth Syst Sci 24:4523–4540. https://doi.org/https://doi.org/10.5194/hess-24-4523-2020
Bubbles and element clusters in rock melts: A chicken and egg problem
Authors: Dubosq Renelle , Pleše Pia , Langelier Brian , Gault Baptiste , Schneider David
Published: March 2021

The nucleation and growth dynamics of gas bubbles and crystals play a vital function in determining the eruptive behaviour of a magma. Their rate and relative timing, among other factors, are controlled by the magma’s ascent rate. Investigating the kinetics of decompression-induced degassing and crystallization processes can thus give us insight into the rheology of magmas. For example, the rapid decompression of magmas inhibits microlite crystallization and bubble nucleation during ascent leading to crystallization and degassing at shallow levels. This results in a drastic increase in viscosity and an over pressured system, which can lead to violent eruptions. Although many experiments and numerical simulations of magma decompression have been carried out, nascent and initial bubble nucleation remain poorly understood. It is widely accepted that there are two ways bubbles can nucleate within a melt: heterogeneous (on a pre-existing surface) and homogeneous nucleation (within the melt), where homogeneous nucleation requires a higher volatile supersaturation. It has since been tentatively suggested that homogeneous nucleation is simply a variety of heterogeneous nucleation where nucleation occurs on the surface of submicroscopic crystals. However, evidence of these crystals is equivocal. Thus, we have combined novel 2D and 3D structural and chemical microscopy techniques including scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS) mapping, and atom probe tomography (APT) to investigate the presence of sub-nanometer scale chemical heterogeneities in the vicinity of gas bubbles within an experimental andesitic melt. The combined STEM and EELS data reveal a heterogeneous distribution of bubbles within the melt ranging between 20-100 nm in diameter, some of which have Fe and/or Ca element clusters at the bubble-melt interface. Element clusters enriched in Fe, Ca, and Na are also observed heterogeneously distributed within the melt. The reconstructed APT data reveals bubbles as low ionic density regions overlain by a Na-, Ca-, and K-rich cluster and heterogeneously distributed Fe clusters within the bulk of the melt. Based on these observations, our data demonstrate the existence of nano-scale chemical heterogeneities within the melt and at the bubble-melt interface of bubbles that were previously interpreted to be nucleated homogeneously within the melt, therefore contributing to the proposed hypothesis that homogeneous nucleation could in fact be a variety of heterogeneous nucleation. These results highlight the need to redefine homogeneous nucleation and revisit whether bubbles or crystals occur first within volcanic melts. 
The O2 aurora observed by the TIMED/SABER satellite
Authors: Gao Hong , Xu Jiyao , Zhu Yajun
Published: March 2021

We studied O2 aurora based on the observations of O2 emission at 1.27 μm from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument during the nighttime over 18 years. The horizontal structure and vertical profile of O2 auroral volume emission rate is obtained after removing O2 nightglow contamination. The O2 auroral intensity varies between 0.14 and 5.97 kR, and the peak volume emission rate varies between 0.97 × 102 and 41.01 × 102 photons cm−3 s−1. The O2 auroral intensity and peak volume emission rate exponentially increases with increasing Kp index, whereas the peak height decreases with increasing Kp index. The O2 auroral intensity and peak volume emission rate under solar minimum condition are larger than those under solar maximum condition. The peak height under solar minimum condition is lower than that under solar maximum condition.
Estimation of the Effects of Regional Climate Change Scenarios on the Water Balance of a Basin in the Middle Magdalena Valley
Authors: Romero-Duque Sergio Andres , Arenas-Bautista Maria Cristina , Donado Leonardo David
Published: March 2021

Hydrological cycle dynamics can be simulated through continuous numerical modelling in order to estimate a water budget at different time and spatial scales, taking a specific importance when considering climate change effects on the various processes that take place on a basin. With the purpose of estimating potential impacts of climate change on the basin water balance, the present study takes place on the catchment area of the Carare-Minero river, a basin located in the Middle Magdalena Valley (Colombia), a zone in which important economic activities unfold such as stockbreeding and agriculture, where regional climate change scenarios were made for the precipitation and temperature variables, along with a continuous hydrological modeling of the basin using the HEC-HMS software. The regional scenarios for the precipitation and temperature were developed through statistical downscaling based on General Circulation Models (GCM) of the sixth phase of the Coupled Intercomparison Project (CMIP6), with projections to 2100 for seven of the new set of CO2 emission scenarios, the Shared Socioeconomic Pathways (SSP), that take into account different socioeconomic assumptions for climate policies, with a baseline of 25 years between 1990 and 2014; the emission scenarios evaluated from lowest to highest CO2 emission were SSP1-1.9, SSP1-2.6, SSP4-3.4, SSP2-4.5, SSP4-6.0, SSP3-7.0 and SSP5-8.5. The obtained data were used as an input for the model of the basin in HEC-HMS obtaining a new water balance for each scenario comparing the results with the baseline case for current conditions, resulting in an evapotranspiration increase due to higher temperatures that, alongside changes in precipitation, produces lower flows for the higher SSP’s of SSP5-8.5 and SSP3-7.0, in contrast with the low emission scenarios of SSP1-1.9 and SSP1-2.6 were the changes in temperature and precipitation are less drastic generating minor alterations in the hydrological balance.

Key words: Hydrological modeling, Middle Magdalena Valley, regional climate change scenarios, water balance.
The effect of stream interaction regions on CME structures: observations in longitudinal conjunction at Mercury and 1 AU
Authors: Scolini Camilla , Winslow Reka M. , Lugaz Noé , Galvin Antoinette B.
Published: March 2021

We present a study of two CMEs observed at Mercury and 1 AU by spacecraft in longitudinal conjunction. Of the two CMEs, one propagated relatively self-similarly, while the other one underwent significant changes in its properties, making them excellent case studies to investigate the following question: what causes the drastic alterations observed in some CMEs during propagation, while other CMEs remain relatively unchanged? Answering this question will also help us better understand the potential impact of CMEs on the near-Earth environment. 

In this work we focus on the presence or absence of large-scale corotating structures in the propagation space between Mercury and 1 AU, that have been shown in the past to influence  the orientation  of  CME  magnetic  structures  and  the  properties  of  CME  sheaths. At both locations, we determine the CME flux rope orientation and characteristics using different fitting and classification methods. Our analysis is complemented by solar wind plasma measurements near 1 AU, by estimates of the size evolution of the sheaths and magnetic ejecta with heliocentric distance, and by the identification of solar wind structures in the CME propagation space based on in situ data, remote-sensing observations, and numerical simulations of the solar wind conditions in the inner heliosphere.

Results indicate that the changes observed in one CME were likely caused by a stream interaction region, while the CME exhibiting little change did not interact with any large-scale structure between Mercury and 1 AU. This work provides end-member examples of CME propagation in the inner heliosphere, exemplifying how interactions  with  corotating  structures  in  the  solar  wind  can  induce  essential  changes  in  CME structures. Our findings provide new fundamental insights on the propagation and evolution of CMEs, and can help lay the foundation for improved predictions of CME properties at 1 AU.