bluuebunny/crossref_metadata_2025 huggingface dataset:
Tropospheric polar BrO derived from S5-P/TROPOMI
Authors: Schöne Moritz , Sihler Holger , Warnach Simon , Borger Christian , Beirle Steffen , Wagner Thomas , Platt Ulrich
Published: March 2021

Halogen radicals can drastically alter the atmospheric chemistry. In the polar regions, this is made evident by the ozone desctruction in the stratosphere (ozone hole) but also by localized destruction of boundary layer ozone during polar springs. These recurrent episodes of catalytic ozone depletion are caused by enhanced concentrations of reactive bromine compounds. The proposed mechanism by which these are released into the atmosphere is called bromine explosion - reactive bromine is formed autocatalytically from the condensed phase.

The spatial resolution of S-5P/TROPOMI of up to 3,5 km x 5.5 km² allows improved localization and a finer specification of these events compared to previous satellite measurements. Together with the better than daily coverage over the polar regions, this allows investigations of the spatiotemporal variability of enhanced BrO levels and their relation to different possible bromine sources and release mechanisms.

Here, we present tropospheric BrO column densities retrieved from TROPOMI measurements using Differential Optical Absorption Spectroscopy (DOAS). We developed an algorithm capable of separating tropospheric and stratospheric partial columns without further external (model) input only relying on measured NO2and O3, by utilizing a modified version of a k-means clustering and other methods from statistical data analysis.

Selected events from the polar springs in 2019 and 2020 are further analyzed and discussed with regards to sea ice coverage and meteorological influences.
Robust technology and policy pathways to urban water security
Authors: Zaniolo Marta , Fletcher Sarah , Mauter Meagan
Published: March 2021

Increasingly frequent and severe droughts are jeopardizing urban water security in water stressed regions, but cities also struggle to justify the costs and energy consumption of some drought-resilient technologies. Previous literature in urban water modeling developed strategies to expand and diversify urban water supply portfolios to enhance water resilience cost effectively.  This literature has also demonstrated that high-resolution, household-level modeling is necessary to represent the real energy footprint of different water technologies and the integration of centralized and decentralized water solutions. This urban-focused modeling scale, however, does not support the characterization of water availability at extra-urban sources resulting from watershed-wide hydrological processes. Conversely, watershed-scale water resources planning characterizes water variability and stress, supports climate change analysis, but overlooks key distributional and technological aspects. 

This project develops a watershed-to-end-user decision support tool for cost-effective, adaptive water augmentation pathways to ensure robustness in many climate futures. The novelty of our work lies in a true multiscale modeling framework that captures the complex system dynamics that link climate impacts to household water security. A robust, multi-objective, evolutionary-based optimization framework (i.e., EMODPS) is used to derive the technology portfolio, deployment location, and construction timing that defines a city’s Pareto frontier of water resilience and cost. This work informs urban water resource planners, as well as guides technology innovation by explicitly valuing technology attributes that enable resilience to droughts of varying duration, severity, and intensity. We apply this model to the City of Santa Barbara, California, given the time relevance to city planning efforts, the diversified water supply mix, and the relative isolation of the community, enclosed between the ocean and a mountain range.
Retrieval of Aerosol Optical Properties over East Asia from TROPOMI using GEMS Aerosol Algorithm 
Authors: Cho Yeseul , Kim Jhoon , Go Sujung , Kim Mijin , Lim Hyunkwang , Torres Omar
Published: March 2021

To better understanding the role of aerosols in climate change and their direct effects on human health, aerosol optical properties have been monitored by various satellite sensors. Successful operations of the Tropospheric Monitoring Instrument (TROPOMI) onboard the Copernicus Sentinel-5 Precursor satellite allow an improved understanding of the wide-ranging variation in aerosol distribution and properties with high spatial resolution since 2018. The Geostationary Environmental Monitoring Spectrometer (GEMS), onboard Geokompsat-2B (GK-2B) satellites, is the first air quality monitoring sensor in geostationary earth orbit and was successfully launched on February 19, 2020. GEMS measures hourly hyperspectral radiances with the spectral resolution of 0.6 nm in UV and visible range (300 – 500 nm) and the spatial resolution of 3.5 x 8 km2 over Asia during the daytime to provide air quality information. TROPOMI which has similar specifications to GEMS, has the advantages of the sensitivity of aerosol absorption and aerosol height information in UV-Vis wavelengths. GEMS aerosol algorithm was applied to the Level 1B data of TROPOMI to retrieve aerosol optical properties such as aerosol optical depth (AOD), UV aerosol index (UVAI), single scattering albedo (SSA), and aerosol loading height (ALH). We present GEMS aerosol retrieval results to discuss high aerosol loading cases over East Asia and analysis results as a case study. Our results show that the GEMS aerosol products have the advantage to capture the fine-scale features of aerosol properties in high spatial resolution. Further, the results are compared to other aerosol products obtained from the Advanced Himawari Imager (AHI) onboard Himawari-8. Qualitatively good agreements and fine-scale features are shown in this case study.
Asymmetry and pathways of inter-hemispheric transport in the upper troposphere and lower stratosphere
Authors: Yan Xiaolu , Konopka Paul , Hauck Marius , Podglajen Aurélien , Ploeger Felix
Published: March 2021

Inter-hemispheric transport may strongly affect the trace gas composition of the atmosphere, especially in relation to anthropogenic emissions which originate mainly in the Northern Hemisphere. This study investigates the transport from the boundary surface layer of the Northern Hemispheric (NH) extratropics (30-90oN), Southern Hemispheric (SH) extratropics (30-90oS), and tropics (30oS-30oN) into the global upper troposphere and lower stratosphere (UTLS) using simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS). In particular, we diagnose inter-hemispheric transport in terms of the air mass fractions (AMF), age spectra, and the mean age of air (AoA) calculated for these three source regions. We find that the AMFs from the NH extratropics to the UTLS are about five times larger than the corresponding contributions from the SH extratropics and almost twenty times smaller than those from the tropics. The amplitude of the AMF seasonal variability originating from the NH extratropics is comparable to that from the tropics. The NH and SH extratropics age spectra show much stronger seasonality compared to the seasonality of the tropical age spectra. The transit time of NH extratropical origin air to the SH extratropics is longer than vice versa. The asymmetry of the inter-hemispheric transport is mainly driven by the Asian summer monsoon (ASM). We confirm the important role of ASM and westerly ducts in the inter-hemispheric transport from the NH extratropics to the SH. However, we find that it is an interplay between the ASM and westerly ducts which triggers such cross-equator transport from boreal summer to fall, mainly westerly ducts over the eastern Atlantic.
40Ar/ 39Ar laser dating of Zongwulong ductile shear zone in northeastern Tibetan Plateau ：Constrains on the closure time of the northmost Paleo-Tethys ocean
Authors: Gao Wanli , Wang Zongxiu
Published: March 2021

Abstract：The Zongwulong tectonic belt (ZTB) is located between the northern Qaidam tectonic belt and the south Qilian orogenic belt and contains Late Paleozoic and Early- Middle Triassic strata. Structural features and geochronology of Zongwulong ductile shear zone have key implications for the tectonic property of the ZTB. This study integrated field structure, microscopic structure and 40Ar/39Ar laser probe analysis. The shear zone strikes ~NEE-SWW and dips at a high angle, with a NWW-SEE trending and WE stretching lineation, indicating the shear zone as a thrust- slip shear ductile shear. The asymmetric folds, rotating porphyroclast,structural lens and crenulation cleavage can be seen in the field. Mica fish, S − C fabrics, σ type quartz porphyroclastic and quartz wire drawing structure can also be observed under microscope, indicating that the strike- slip- related ductile deformation and mylonitization occurred under low- grade greenschist facies conditions at temperatures of 300° C − 400° C.  The highly deformed
mylonite schist yielded 40Ar/39Ar ages (245.8±1.7)Ma and (238.5±2.6)Ma for muscovite and biotite, respectively, indicating that the shear deformation occurred during the Early- Mid Triassic. Combined with comprehensive analysis of regional geology and petrology, the authors hold that the age of ductile shear deformation represents the time of Triassic orogeny in the ZTB. The oroginic activity was probably related to the oblique collision between the South Qilian block and the Oulongbuluke block after the closure of the northermost Paleo-Tethys ocean.
Radiocesium contamination in wild mouse in Fukushima, Japan
Authors: Ishiniwa Hiroko , Tamaoki Masanori , Endoh Daiji , Onuma Manabu
Published: March 2021

The large Japanese field mouse (Apodemus speciosus) which endemic wild mice living in Japanese forest, was monitored after the Fukushima nuclear power plant released a large amount of radioactive materials due to accident. We will introduce current status of radiocesium contamination, estimated radiation dose, and effect in the field mouse. According to calculation of radiation dose using Monte Carlo electron-photon transport code EGS5, it was clarified that dose rate level of the field mouse fall under derived consideration reference level determined by ICRP. Analysis of the oxidative stress in male mice testis revealed the damage in testicular cells of mice collected in 2012, when monitoring began.
Historical change of winter Tibetan Plateau snow cover and its controlling factors
Authors: Li Shixue , Sato Tomonori , Nakamura Tetsu
Published: March 2021

This study investigates the controlling factors of the interannual variability of Tibetan Plateau snow cover (TPSC) in winter. Since snow observation in Tibetan Plateau is limited in space and time, high-resolution multi-satellite data for TPSC were analyzed during 1982-2016. In addition, a large ensemble AGCM experiment from d4PDF (hereafter, HIST), driven by observed SST and anthropogenic forcings were analyzed during 1951-2010 to compare the contributions arising from internal variability and external forcings including the change in greenhouse gases (GHGs) concentration on TPSC variation. In this study TPSC fraction (hereafter, TPSCF) is defined as the percentage of the snow-covered area over the Tibetan Plateau. For both observation and HIST, high and low TPSCF years determined by the standardized January-March TPSCF were analyzed. The range of interannual TPSCF variation (i.e., TPSCF difference between high and low TPSCF years) is about 11% in both observation and the model, suggesting the AGCM well reproduced the TPSCF variability in the interannual timescale. 

We found that high TPSCF is linked to a positive-AO-like pattern. The interannual variation of the observed AO index and TPSCF are significantly correlated. In d4PDF high TPSCF more likely appears with a higher (positive) AO index and vice versa. In high TPSCF years, the subtropical jet is strengthened, which significantly enhances zonal water vapor flux reaching the plateau supporting more precipitation. Another interesting result is a disagreement for ENSO’s contribution to TPSC appears between observation and HIST. However, several members in HIST show a feature close to the observation, in which TPSCF anomalies are not sensitive to the El Niño/La Niña events. Thus, this weak linkage between ENSO and TPSCF is more likely due to the limited cases of observations rather than the model bias. Finally, by comparing HIST and non-warming experiments (NAT), we found historical global warming has decreased the snow-to-rain ratio over TP. Nonetheless, increased precipitation compensates for it. As a result, the impact of historical global warming on TPSCF could be considered negligibly weak.
Vertical distribution of trace gases and aerosols over the Russian Arctic in September 2020
Authors: Belan Boris D. , Antokhin Pavel , Antokhina Olga , Arshinova Victoriya , Arshinov Mikhail , Belan Sergey , Davydov Denis , Ivlev Georgii , Kozlov Artem , Kozlov Alexandr , Okhlopkova Olesya , Rasskazchikova Tatyana , Savkin Denis , Safatov Alexandr , Simonenkov Denis , Tolmachev Gennadii , Fofonov Alexandr
Published: March 2021

In 2020, a unique experiment, which had ever been implemented either in the former USSR or in modern-day Russia, was carried out in the Russian Arctic by means of the Optik Tu-134 aircraft laboratory operated by IAO SB RAS. The airborne measurement campaign was conducted on September 4-17 over all seas and coastal regions of the Russian sector of the Arctic, including northern part of the Bering Sea.

During the flights, in situ measurements of CO, CO2, CH4, NO, NO2, SO2, O3, aerosols, and black carbon (BC) were performed. Air samples were taken to determine organic and inorganic compounds and biological material in aerosol particles. A remote sensing of the water turbidity in the upper sea layers was conducted by means of the LOZA-2 lidar that allowed a concentration of plankton to be derived there. Spectral characteristics of the water and underlying coastal surfaces were measured using a spectroradiometer.

The primary analysis of the obtained data showed that concentrations of CO, NO, NO2, SO2, O3, aerosols, and BC during the experiment were low that is typical for background regions. CO2 mixing ratios in the lowest part of the troposphere above seas were lower than aloft. As compared with coastal areas, concentration of methane over all the seas of the Arctic sector and the Bering Sea was higher.

We would like to acknowledge our colleagues from the following organizations for their assistance in organizing and conducting this campaign, and in particular, Laboratoire des sciences du climat et de l'environnement and Laboratoire atmosphères, milieux, observations spatiales (France); Finnish Meteorological Institute and Institute for Atmospheric and Earth System Research, University of Helsinki (Finland); Center for Global Environmental Research at the National Institute for Environmental Studies (Japan); the National Oceanic and Atmospheric Administration, US Department of Commerce (USA); Max-Planck-Institute for Biochemistry (Germany); and University of Reading (UK).
Influence of temperature on the hydrothermal clay soils' shear strength of the Nizhne-Koshelevsky and Verkhne-Pauzhetsky thermal fields.
Authors: Kuznetsov Ruslan , Chernov Mikhail , Krupskaya Victoria , Khamidov Ruslan
Published: March 2021

Nizhne-Koshelevskoe and Verkhne-Pauzhetskoe thermal fields are located in the south of Kamchatka, the first - within the Koshelevsky volcanic massif, the second - on the territory of the Pauzhetsky geothermal field. The first horizon from the surface in these fields is formed by clayey soils, that have been formed as a result of hydrothermal alteration of volcanic rocks. And in the natural conditions clayey soils are at temperatures reaching 100 °C.

Samples of undisturbed clay soils were taken within the thermal fields. The samples are characterized by a density of 1.29 - 1.42 g/cm3, rather high values of the weight moisture (90-110%), and temperatures of 50 - 70 °C.

The samples are dominated by clay minerals: kaolinite and mixed-layer - kaolinite-smectite, their content is about 75%. The other 25% are microcline, cristobalite, anatase, gypsum, pyrite, marcasite, quartz and alunite.

For samples of undisturbed clay soils, direct shear tests were carried out at a temperature of 20 °C and at a temperatures of the samples close to their natural temperatures (50–70 °C). Thus, the values of cohesion and the angle of internal friction of the samples were determined.

The obtained results can be interfered as follows: as a result of an increase in the temperature of clayey soils, the thickness of electric double layer on the surface of clay particles decreases. On the one hand, it leads to a decrease of cohesion value between the clay particles and the beginning of shear deformations at lower vertical loads. On the other hand, a smaller thickness of electric double layer brings particles closer to each other, which is the reason for an increasing angle of internal friction and shear resistance at higher vertical loads.
Seasonality of sea ice deformation at MOSAiC
Authors: Hutchings Jennifer , Bliss Angela , Basu Rajlaxmi , Cheng Bin , Itkin Polona , Krumpen Thomas , Lei Ruibo , Haapala Jari , Haas Christian , Hoppmann Mario , Hwang Phil , Persson Ola , von Albedyll Luisa , Watkins Daniel
Published: March 2021

Sea ice drift and deformation shapes the ice cover of the polar oceans, lead opening modulating heat transfer across the ice pack and deformation driven roughness changes affecting momentum transfer from winds and currents. Yet we do not fully understand the seasonal evolution of sea ice deformation. An array of >95 GPS drifting buoys and 11 ice stations was deployed as a Distributed Network around the MOSAiC Central Observatory, capturing scales of sea ice motion between hundreds of meters to up to 200 kilometers. The array drifted across the Arctic in the transpolar drift in less than a year, with an anomalous east-west sea level pressure gradient driving the fast drift. The buoys monitored horizontal deformation of the pack ice from freeze up north of the Laptev Sea to melt in the Greenland Sea. The deformation responds to inertial motion during the freeze up transition to a consolidated ice pack. The fractal dimension of the total deformation changes throughout the year. At smaller scales of about 10 km deformation becomes whiter during the growth season, once the ice pack is consolidated to the coast. There iis an increase in episodic events at the largest scales during the periods the ice pack is consolidated and where it becomes more tidally active during transition through Fram Strait. The MOSAiC distributed network brings improved understanding in the transition of sea ice deformation from freedrift to pack ice, and the response of the ice to changing momentum transfer from the wind and ocean across the Transpolar Drift. The MOSAiC campaign provides unprecedented information about the atmospheric structure and spatial distribution of winds, as well as near surface currents, from which we can deduce the affect of sub-mesoscale deformation in the wind field on the horizontal ice deformation. 
Persistent El Nino driven shifts in marine cyanobacteria populations
Authors: Larkin Alyse , Moreno Allison , Fagan Adam , Martiny Adam
Published: March 2021

From 2014 through 2016, a significant El Niño event and the North Pacific warm anomaly (a.k.a., “the blob”) resulted in a marine heatwave across the Eastern North Pacific Ocean. To develop a deeper understanding of the impacts of El Niño on the Southern California Bight (SCB), we used coastal cyanobacteria populations in order to “bi-directionally” link shifts in microbial diversity and biogeochemical conditions. We sequenced the rpoC1 gene from the ecologically important picocyanobacteria Prochlorococcus and Synechococcus at 434 time points from 2009–2018 in the MICRO time series at Newport Beach, CA. Across the time series, we observed an increase in the abundance of Prochlorococcus relative to Synechococcus as well as elevated frequencies of clades commonly associated with low-nutrient and high-temperature conditions. The relationships between environmental and diversity trends appeared to operate on differing temporal scales. In addition, microdiverse populations from the Prochlorococcous HLI clade as well as Synechococcus Clade II that shifted in response to the 2015 El Niño did not return to their pre-heatwave composition by the end of this study. This research demonstrates that El Niño-driven warming in the SCB can result in persistent changes in key microbial populations.
Core-CT:  A MATLAB application for the quantitative analysis of sediment and coral cores from X-ray computed tomography (CT) 
Authors: Yan Yu Ting , Chua Stephen , DeCarlo Thomas , Kempf Philipp , Morgan Kyle , Switzer Adam
Published: March 2021

X-ray computed tomography (CT) is a non-destructive imaging technique that provides three-dimensional (3D) visualisation and high-resolution quantitative data in the form of CT numbers. CT numbers are derived as a function of the X-ray energy, effective atomic number and density of the sample. The sensitivity of the CT number to changes in material density allows it to successfully identify facies changes within sediment cores by detecting downcore shifts in sediment properties, and quantify skeletal linear extension rates and the volume of internal voids from biological erosion of coral cores. Here we present two algorithms to analyse CT scan images specific to geoscience research packaged within an open source MATLAB application (Core-CT). The first algorithm facilitates the computation of representative CT numbers from a user-defined region of interest to identify boundaries of density change (e.g. sedimentary facies, laminations, coral growth bands). The second algorithm enables the segmentation of regions with major density contrast (e.g. internal void space or biogenic material) and the geometric measurements of these irregularities. The versatility of Core-CT for geoscience applications is then demonstrated by utilising CT scans from a range of environmental settings comprising both sediment (Lake Huelde, Chile and Kallang River Basin, Singapore) and coral cores (Thuwal region of Red Sea, Saudi Arabia). Analysis of sediment cores show the capabilities of Core-CT to: 1) locate tsunami deposits from lacustrine sediments, 2) provide rapid and detailed measurement of varved sediments, and 3) identify sedimentary facies from an unsplit shallow marine sediment core. Analysis of coral cores allow us to successfully measure skeletal linear extension from annual growth bands, and provide volumetric quantification and 3D visualisation of internal bioerosion. Core-CT is an accessible, multi-use MATLAB based program that is freely available at GitHub  (https://github.com/yuting-yan/Core-CT).

 
A study on the dynamic process of fluid mud and its effect on siltation in the Yangtze Estuary Deepwater Channel
Authors: Li Yue , Hu Peng , Li Ji
Published: March 2021

The Yangtze Estuary Deepwater Channel Project has brought great economic and social benefits since its completion, but the siltation problem is still worthy of attention. In order to investigate the mechanisms of fluid mud in the estuary and to study the influence of fluid mud on siltation in the Yangtze Estuary Deepwater Channel, a two-dimensional physically-enhanced two-layer flow model will be developed in this paper. The model includes two series of governing equations which are about environment fluid and fluid mud, respectively. The model is based on the unstructured grid, and the governing equations are discretized by the finite volume method, and the improved LTS/GMaTS technology is used to improve the computational efficiency. Firstly, an experiment that the fluid mud was flowing underwater along a gentle slope is reconstructed by the two-layer model. It shows the ability of the model to describe the simple movement of fluid mud. Secondly, the model is applied to Yangtze Estuary. Without the fluid mud layer, the model can be simplified as a tide-current model. The reliability of the tidal current and tide level is verified, and it means the model can describe the tide accurately. Based on this, the process of formation, transport, and break-down of fluid mud is simulated and its effect on the siltation in the Yangtze Estuary Deepwater Channel is estimated.
Use of nitrogen as a tool for the study of the trophic state of vulnerable coastal ecosystems
Authors: Camacho-Cruz Karla , Rey-Villiers Nestor , Medina-Contreras Diana , Gonzalez-Jones Paula , Arenas-Gonzalez Fernando , Sanchez-Gonzalez Alberto
Published: March 2021

Concentration and flux of nitrogen in mangrove wetlands and coral reefs are modified by chemical and hydrodynamic mechanisms determined by natural and anthropic factors. Nearby anthropic activities impact ecosystems making them vulnerable, mainly due to nutrient flow increase which modifies biogeochemical cycles and trophic dynamics. Here, spatial-temporal variability of N in three tropical coastal ecosystems under different levels of anthropic pressure were studied; 1) trophic dynamics of mangroves in the Colombian Pacific using stable isotopes (δ13C, δ15N); 2) quantification of δ15N in octocorals from the northwestern region of Cuba as an indicator of wastewater pollution, and 3) determination of the trophic status of coastal and continental sites in the Mexican Caribbean using Karidy’s index and CE-CCA-001-89. In the mangrove food web, a value of 5 ‰ for δ15N was found, principally in systems with modified trophic structures close to tourist and urban centers. In octocorals, δ15N was significantly higher in reefs close to polluted river basins, evidencing a positive and significant correlation with the concentration of fecal and total coliforms, fecal streptococci, heterotrophic and sulfate-reducing bacteria. The nutrients analyzed in the Mexican Caribbean, exceeded the permissible limit for the protection of marine life, with Karidy’s index suggesting in some sites concentrations of nitrates in a mesotrophic and eutrophic state, principally during the months of highest tourist influx. The results confirm the effect and vulnerability of these ecosystems towards anthropic N, which could result in a reduction of ecosystem services and diversity.
Evaluating the ability of NA-CORDEX to simulate the seasonal modes of precipitation variability across the Western United States: Does resolution matter?
Authors: Meyer Jonathan , Wang Shih-Yu (Simon) , Gillies Robert , Yoon Jin-Ho
Published: March 2021

The western U.S. precipitation climatology simulated by the NA-CORDEX regional climate model ensembles are examined to evaluate the capability of the 0.44° and 0.22° resolutionensembles to reproduce 1) the annual and semi-annual precipitation cycle of several hydrologically important western U.S. regions and 2) localized seasonality in the amount and timing of precipitation. Collectively, when compared against observation-based gridded precipitation, NA-CORDEX RCMs driven by ERA-Interim reanalysis at the higher resolution 0.22° domain resolution dramatically outperformed the 0.44° ensemble over the 1950-2005 historical periods. Furthermore, the ability to capture the annual and semi-annual modes of variability was starkly improved in the higher resolution 0.22° ensemble. The higher resolution members reproduced more consistent spatial patterns of variance featuring lower errors in magnitude—especially with respect to the winter-summer and spring-fall seasonality. A great deal of spread in model performance was found for the semi-annual cycles, although the higher-resolution ensemble exhibited a more coherent clustering of performance metrics. In general, model performance was a function of which RCM was used, while future trend scenarios seem to cluster around which GCM was downscaled.

Future projections of precipitation patterns from the 0.22° NA-CORDEX RCMs driven by the RCP4.5 “stabilization scenario” and the RCP8.5 “high emission” scenario were analyzed to examine trends to the “end of century” (i.e. 2050-2099) precipitation patterns. Except for the Desert Southwest’s spring season, the RCP4.5 and RCP8.5 scenarios show a consensus change towards an increase in winter and spring precipitation throughout all regions of interest with the RCP8.5 scenario containing a greater number of ensemble members simulating greater wetting trends. The future winter-summer mode of variability exhibited a general consensus towards increasing variability with greatest change found over the region’s terrain suggesting a greater year-to-year variability of the region’s orographic response to the strength and location of the mid-latitude jet streams and storm track. Increasing spring-fall precipitation variability suggests an expanding influence of tropical moisture advection associated with the North American Monsoon, although we note that like many future monsoon projections, a spring “convective barrier” was also apparent in the NA-CORDEX ensembles.
Revealing seasonal crustal seismic velocity variations in Taiwan with single-station cross-component analysis 
Authors: Feng Kuan-Fu , Huang Hsin-Hua , Hsu Ya-Ju , Wu Yih-Min
Published: March 2021

Ambient noise interferometry is a promising technique for studying crustal behaviors, providing continuous measurements of seismic velocity changes (dv/v) in relation to physical processes in the crust over time. In addition to the tectonic-driven dv/v changes, dv/v is also known to be affected by environmental factors through rainfall-induced pore-pressure changes, air pressure loading changes, thermoelastic effects, and so forth. In this study, benefiting from the long-term continuous data of Broadband Array in Taiwan for Seismology (BATS) that has been operated since 1994, we analyze continuous seismic data from 1998 to 2019 by applying single-station cross-component (SC) technique to investigate the temporal variations of crust on seismic velocity. We process the continuous waveforms of BATS stations, construct the empirical Green’s functions, and compute daily seismic velocity changes by the stretching technique in a frequency band of 0.1 to 0.9 Hz. We observe co-seismic velocity drops associated with the inland moderate earthquakes. Furthermore, clear seasonal cycles, with a period of near one-year, are also revealed at most stations, but with different characteristics. Systematic spectral and time-series analyses with the weather data are conducted and show that the rainfall-induced pore-pressure change is likely the main cause to the seasonal variations with high correlations. The strong site-dependency of these seasonal variations also precludes air pressure and temperature which varies smoothly in space from being dominant sources and suggests spatially-varying complex hydro-mechanical interaction across the orogenic belt in Taiwan.
The diminishing contribution of low-level jets to the U.S. Great Plains water budget
Authors: Ferguson Craig R.
Published: March 2021

In the semi-arid U.S. Great Plains, nocturnal southerly low-level jets (LLJs) serve critical roles as conveyors of remotely-sourced (i.e., Gulf of Mexico) water vapor and agents of atmospheric instability in the warm-season.  Defined by a diurnally oscillating wind maximum between 0–3 km above the surface, LLJs have been studied by meteorologists for over 60-years due to their role in severe weather outbreaks. It is only within the past decade that a subset of LLJs with especially high vertically integrated water vapor transport, termed atmospheric rivers, have drawn the attention of hydrologists.

In this study, changes in LLJ frequency and structure over the period from 1901–2010 are quantified using ECMWF’s Coupled Reanalysis of the Twentieth Century (CERA-20C). A new objective dynamical LLJ classification dataset is used to separately quantify changes in the two predominant LLJ types: synoptically coupled and uncoupled. The findings reveal that both the frequency of Great Plains LLJs and their associated precipitation have decreased significantly over the 20th century. Decreases in LLJ associated precipitation range between 10–14% of total present day May–September precipitation. The largest differences observed are attributable to uncoupled jet frequency and structural changes during July and August over the central and northern Great Plains. Overall, the results indicate the contribution of LLJs to the region’s water budget has diminished.
Unified model of sediment transport threshold and rate across subaqueous bedload, windblown sand, and windblown snow
Authors: Pähtz Thomas , Liu Yonghui , Xia Yuezhang , Hu Peng , He Zhiguo , Tholen Katharina
Published: March 2021

Nonsuspended sediment transport (NST) refers to the sediment transport regime in which the flow turbulence is unable to support the weight of transported grains. It occurs in fluvial environments (i.e., driven by a stream of liquid) and in aeolian environments (i.e., wind-blown) and plays a key role in shaping sedimentary landscapes of planetary bodies. NST is a highly fluctuating physical process because of turbulence, surface inhomogeneities, and variations of grain size and shape and packing geometry. Furthermore, the energy of transported grains varies strongly due to variations of their flow exposure duration since their entrainment from the bed. In spite of such variability, we here propose a deterministic model that represents the entire grain motion, including grains that roll and/or slide along the bed, by a periodic saltation motion with rebound laws that describe an average rebound of a grain after colliding with the bed. The model simultaneously captures laboratory and field measurements and discrete element method (DEM)-based numerical simulations of the threshold and rate of equilibrium NST within a factor of about 2, unifying weak and intense transport conditions in oil, water, and air (oil only for threshold). The model parameters have not been adjusted to these measurements but determined from independent data sets. Recent DEM-based numerical simulations (Comola, Gaume, et al., 2019, https://doi.org/10.1029/2019GL082195) suggest that equilibrium aeolian NST on Earth is insensitive to the strength of cohesive bonds between bed grains. Consistently, the model captures cohesive windblown sand and windblown snow conditions despite not explicitly accounting for cohesion.
Modelling the contribution of ice cliff melt to glacier mass loss at the catchment scale
Authors: Buri Pascal , Miles Evan S , Steiner Jakob , Ragettli Silvan , Pellicciotti Francesca
Published: March 2021

The melt rates of debris-covered glaciers in High Mountain Asia are highly heterogeneous and poorly constrained. Supraglacial cliffs are typical surface features of debris-covered glaciers and act as windows of energy transfer from the atmosphere to the ice, locally enhancing melt and mass losses of otherwise insulated ice. Despite this, their contribution to the glacier mass budget has never been quantified at the glacier scale.

Here we simulate the specific melt of all supraglacial ice cliffs individually in a Himalayan catchment (Langtang Valley, Nepalese Himalayas), using a process-based ice cliff melt model that has previously been validated in the catchment. Cliff outlines and initial topography are derived from high-resolution stereo SPOT6-imagery and the model is forced by meteorological data from on- and off-glacier automatic weather stations within the valley, both for the 2014 melt season. The model simulates ice cliff backwasting by considering the cliff-atmosphere energy-balance, reburial by debris and the effects of adjacent ponds. We estimate the contribution of ice cliffs to glacier surface mass balance derived from ensemble mean geodetic thinning observations and emergence flux calculations for the same glaciers 2006-2015.

We show that ice cliffs, although covering only 2.1 ±0.6 % of the debris-covered tongues, are partially responsible for the high thinning rates of debris-covered glacier tongues, leading to a catchment mass loss underestimation of 17 ±4 % if not considered. We show that cliffs enhance melt where other processes would suppress it, i.e. at high elevations or where debris is thick, and confirm that they contribute relatively more to glacier mass loss if oriented north.

Our approach bridges a scale gap in our understanding of the processes of debris-covered glacier mass losses, and a new quantification of their catchment wide melt and mass balance.
Turbidites, benthic foraminifera, and earthquakes – a paleoseismic record from the northern Gulf of Aqaba 
Authors: Bookman Revital , Ash-Mor Anat , Kanari Mor , Ben Avraham Zvi , Almogi Ahuva
Published: March 2021

Submarine mass transport deposits (MTDs) and turbidites are a well-known phenomenon in tectonically active regions. Evidence for such deposits is commonly found in the continental slope sedimentary records as distinct units with coarser grain size compared to the continuous pelagic sedimentation. The Gulf of Eilat/Aqaba is located between the southernmost end of the Dead Sea transform and the spreading center of the Red Sea, and is considered as an active tectonic region. In this study, symbiont-bearing Larger Benthic Foraminifera (LBF) were used to identify MTDs in the Gulf of Eilat/Aqaba (GEA) sedimentary record. The abundance, size and preservation state of LBF shells were analyzed in two radiocarbon dated sediment cores collected at different deposition environments at the deep GEA slope.

The microfaunal and taphonomic results show that the coarse units are characterized by a generally higher numerical abundance of LBF, dominated by Operculina ammonoides, Amphistegina papillosa and Amphistegina bicirculata. These benthic assemblages are found in deeper depths than their original habitat at the continental shelf. In the coarse units, LBF> 1 mm appear in higher frequency and poorly preserved shells are also abundant. In addition, these units contain high numbers of yellowish and blackish colored LBF shells, as opposed to null in the non-disturbed units, and unlike their natural pristine white color. The large shell size indicates that high energy is involved in the displacement of the  sediments. The poor state of preservation also suggests a turbulent flow during transportation, which requires a high-energy triggering mechanism. The color alteration is probably associated with a diagenetic process related to increasing burial time/depth, also supported by the stratigraphic older ages of the MTDs, suggesting a long burial before the sediments were displaced. Radiocarbon dating reveled most of the MTDs correlate with historical and pre-historical earthquakes, reinforcing LBF species as a reliable proxy for mass transport events.
Why are the van der Waals forces repulsive for interactions of bubbles with solid-water interface?
Authors: Shen Chongyang
Published: March 2021

Understanding interactions of bubbles with surfaces in water is critical to a variety of engineered applications and environmental concerns such as delivery of the nanobubbles for in-situ soil remediation and use of flotation in water treatment. van der Waals (VDW) force is one of the main forces controlling the interaction between a colloid and a surface in electrolyte solution. It has been recognized that the VDW force is repulsive between a solid surface and a colloid if it is a bubble. Thus, the bubbles did not stick to walls in water. However, it is still not very clear about the mechanisms controlling the repulsive VDW interactions between bubbles and walls to date. Here we used the Hamaker approach to develop an analytical model to quantify the interaction between bubbles and surfaces in water. We provided explanation for why the bubble-surface interaction is repulsive in water. Our findings have important implication to undertanding the natural and engineered processes that involve bubbles in aqutic environments.
A Statistical Reconstruction of Sea-Surface Temperature and Sea-Ice Concentration for the Last Glacial Maximum
Authors: Astfalck Lachlan , Williamson Daniel , Gandy Niall , Gregoire Lauren , Ivanovic Ruza
Published: March 2021

Recent geoscience and palaeoclimatic modelling advances in have seen an increasing demand for spatio-temporal reconstructions of climatic variables. Satisfactory reconstructions should consider all sources of information: both numerical model ensembles and measured data. The difficulty in modelling climatic variables often gives rise to a multiplicity of models due to large uncertainty in the inputs. Climate proxy-based measurements are similarly uncertain due to both measurement noise and reconstruction error. It is thus vital to provide a reconstruction methodology in which these uncertainties are appropriately quantified. Instead of utilising probability based approaches that can be very computationally demanding for geospatio-temporal problems, we have developed a new approach to do this utilising a second-order framework; namely, Bayes linear analysis. This framework avoids the explicit specification of probability distributions and allows reconstructions to be described simply by means and variances. Methodological advances are made to the traditional Bayes linear mechanics to allow for non-linearity. To demonstrate the methodology, average monthly spatial reconstructions of sea-surface temperature and sea-ice concentration are estimated for the Last Glacial Maximum (21 ka), combining PMIP3 and PMIP4 outputs and available palaeodata syntheses. The methodology presented is generalisable to many spatio-temporal quantities and is highly germane to the geoscience community. 
Role of equatorial waves and convective gravity waves in the 2015/16 QBO disruption
Authors: Kang Min-Jee , Chun Hye-Yeong , Garcia Rolando
Published: March 2021

In winter 2015/2016, the descent of the westerly phase of the quasi-biennial oscillation (QBO) was unprecedentedly disrupted by the development of easterly winds. Previous studies have shown that extratropical Rossby waves propagating into the tropics were the major cause of the 2015/16 QBO disruption. However, a large portion of the negative momentum forcing driving the disruption still stems from equatorial planetary and gravity waves, which calls for detailed analyses by separating each wave mode. In this study, the contributions of resolved equatorial planetary waves (Kelvin, Rossby, mixed Rossby–gravity (MRG), and inertia–gravity (IG) waves) and small-scale convective gravity waves (CGWs) obtained from an offline CGW parameterization to the 2015/16 QBO disruption are investigated using MERRA-2 global reanalysis data. In October and November 2015, anomalously strong negative forcing by MRG and IG waves weakened the QBO jet at 0–5°S near 40 hPa, possibly leading to Rossby wave breaking at the QBO jet core in the Southern Hemisphere. From December 2015 to January 2016, strong Rossby waves propagating horizontally (vertically) from the Northern Hemisphere (troposphere) decelerated the southern (northern) flank of the jet. In February 2016, when the westward CGW momentum flux at the source level was much stronger than the climatology, CGWs began to exert considerable negative forcing at 40–50 hPa near the Equator, in addition to the Rossby waves. The enhancement of the negative wave forcing in the tropics stems mostly from strong wave activity in the troposphere associated with increased convective activity and the westerly anomalies in the troposphere, except that the MRG wave forcing is more likely associated with increased barotropic instability in the lower stratosphere.
Numerical simulations of tsunami generation in caldera lakes by subaqueous explosive volcanism
Authors: Hayward Matthew , Whittaker Colin , Lane Emily , Power William
Published: March 2021

Caldera lakes are prominent volcanic features that can pose an additional hazard due to water presence, such as tsunamis, lahars, or flooding by lake breakout. Many of these lakes are populated and occupied by infrastructure on their shore, such as hydroelectric facilities. Volcanogenic tsunamis are a lesser modelled hazard compared to their seismogenic relatives, and the understanding of wave-making potential from subaqueous explosive eruptions is poor due to practical limitations of volcanic observation. Prior studies utilised models of surface waves produced from analogous chemical and nuclear explosions; however, these are derived from dated naval research and require reassessment.

This study verifies a non-hydrostatic, vertically-Lagrangian multilayer method from the open-source software Basilisk against a laboratory flume experiment to assess suitability for modelling waves produced by variable size disturbances. This is then used to evaluate free-surface initial condition models of shallow water explosions on a U.S. Army submerged explosive series on generating waves in Mono Lake, California. On establishing fitness of the underlying models, these are applied to simulate hypothetical scenarios of submarine eruptions at Lake Taupō, New Zealand. Event locations and disturbance sizes are chosen corresponding to vent sites and magnitudes of eruptions during the Holocene. The initial disturbance is fitted to a function of estimated eruption energy. Vulnerable areas include small settlements across the eastern shore, Taupō township and the lake outflow control gates. After the initial tsunami waves, a seiche of lower amplitude is established in the hour following the event. Such eruptions in lakes may pose multiple simultaneous hazards with minimal arrival times (< 15 minutes for tsunami waves at Taupō); therefore the modelling of eruptive scenarios is a primary approach to inform local area hazard maps of submarine volcanism and raise preparedness for surrounding facilities and communities.
The Role of El Niño in Modulating the Effects of Deforestation in the Maritime Continent
Authors: lee Tinghui , lo Minhui
Published: March 2021

The deforestation rate in the Maritime Continent (MC) has been accelerating during the past several decades. Understanding the changes in local hydro-climatological cycles as deforestation takes place is essential because the MC is suffering from frequent and extreme droughts and fires, which often occur during the dry season and are more severe during El Niños. Therefore, this study explores how deforestation affects the hydrological cycle and precipitation in the MC during El Niños, focusing on the boreal autumn season and using the coupled atmosphere-land model simulations. It is found that the precipitation over the MC increases in the deforestation experiments, and the precipitation responses can be magnified during El Niño events. A strong subsidence anomaly associated with El Niño does not prevent enhanced convection associated with local deforestation. Instead, the subsidence reduces the cloud cover in the MC region during El Niño, which increases the incoming solar radiation and increases surface temperatures. Under a warmer environment induced by El Niño, the nonlinear biogeophysical feedbacks associated with deforestation also play a critical role in more substantial land surface warming. A warmer land surface induces a more unstable atmospheric environment associated with a tendency toward enhanced local convection and lateral moisture convergence. This study highlights how the different mean climate states may modulate the impact of local land-use changes on hydroclimatological cycles in the Maritime Continent, and sheds light on the state of our knowledge of interactions between the local land surface and remote large-scale atmospheric circulations.