bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of submarine groundwater discharge on fecal indicator bacteria in a fish culture zone in Tolo Harbour, Hong Kong
Authors: Cheng Kaihao , Luo Xin , Jiao Jiu Jimmy , Yu Shengchao
Published: March 2020

SGD can significantly alter salinity and temperature of coastal waters and also deliver abundant nutrients and anthropogenic substances, such as pathogens, toxins and other pollutants. Contaminated groundwater has been proven to be the sources of fecal indicator bacteria (FIB), which is the sum of total coliform, fecal coliform (i.e., E.coli) and Enterococcus. FIB is highly influential to the public health and fishery management. This study sought to investigate the effects of SGD on the E.coli concentrations in a representative surf zone. A total of 82 nearshore coastal water and 78 coastal groundwater samples were monthly collected from July, 2019 to January, 2020 for radon (Rn), E.coli and nutrients analyses, together with the measurements of concurrent water temperature and salinity. A good positive correlation between the coastal water Rn activity and E.coli concentrations was found with a coefficient of determination (R2) of 0.56, indicating that the SGD mounts a positive effect on the E.coli over the study period including wet and dry seasons. For each sampling period, the slope (K) of each regression model represents the increasing rate of E.coli per unit of Rn activity. The averaged E.coli concentrations (11.5 – 65.5 cfu/100 ml) for each month were inversely correlated to the averaged coastal water salinity (29.8 – 34.0 PSU) with a R2 of 0.66; and the inhibited temperature of E.coli was observed to be 30 ℃. For groundwater, a stronger positive linear correlation between the Rn activity and E.coli concentrations was reported with a R2 of 0.87. As the temperature and salinity of groundwater were almost constant, the K was not much changed. Also, compared to the coastal seawater, groundwater showed a better correlation as the temperature and salinity in groundwater were relatively constant. On the other hand, the regression model of Rn activity and E.coli in groundwater showed that the E.coli was not changed significantly when the Rn activity reached to near 1400 dpm L-1, which means high SGD inputs may not always lead to lasting growth of E.coli.
Experiments on the grain size gap across gravel-sand transitions
Authors: Dingle Elizabeth , Venditti Jeremy
Published: March 2020

An abrupt transition in river bed grain size occurs from gravel to sand over a short downstream distance, often only a few channel widths, and is termed the gravel-sand transition. At this point, the bed structure also changes from framework- to matrix-supported. Whether the gravel-sand transition is externally imposed, a result of internal dynamics (sediment sorting, abrasion, suspension deposition) or due to some other emergent property is unclear. Interestingly, there is a general absence of rivers beds with median surface grain sizes between ~1 and 5 mm. Here we present a new global compilation of gravel-sand transition characteristics across a diverse range of settings. We identify commonalities in the location of gravel-sand transitions, finding they occur at upstream extents of externally imposed backwater effects, where the gravel supply is exhausted (i.e. downstream of mountain ranges), or where both effects are coincident. A series of laboratory channel experiments, examining changes in fluid and sediment dynamics across a gravel-sand transition, show systematic changes in near bed turbulence that control sand deposition patterns. Gravel coarser than ~10 mm prevents sand deposition at the bed surface. We also find that gravel-sand transitions cannot form where river beds contain substantial amounts of ~1 to 5 mm particles, because these grain sizes enhance the mobility of coarser gravel, preventing a shift to a sand bed.
Ice preservation and landscape erosion during glacial retreat on Earth and Mars
Authors: Koutnik Michelle , Pathare Asmin , Todd Claire , Johnson Emily
Published: March 2020

Active glacial environments exhibit characteristic landforms due to the interplay of ice, climate, soil, and rock. These landforms are used as indicators of past and present climate conditions, and the base of knowledge established by studying glacial morphologies on Earth has been applied to aid interpretation of ice-rich or ice-remnant landforms on Mars. We focus on how glaciers and glacial landforms act to erode their surrounding landscape when they are active, and how they are preserved on the landscape when climate changes and ice retreats. This includes specific study of glaciers, debris-covered glaciers, rock glaciers, and cirques because glaciers act to erode landscapes, and landscapes contribute debris that can preserve glacier ice. We contextualize lobate debris aprons and glacier-like forms on Mars with debris-covered glaciers on Earth in order to put the latest research on both planets in a perspective aimed at maximizing process-based understanding of glacier evolution and ice preservation. While we primarily focus on processes controlling active debris-covered glaciers, a key to understanding glacier change through time is to consider individual landforms in context with the full-system environment in which they are found. We discuss process-based progressions and relationships between glacial landforms as understood on Earth; for example, the development of clean-ice glaciers, debris-covered glaciers, rock glaciers, moraines, and talus may be determined as a function of ice movement and debris input.

Building from our current knowledge of Mars, we show results from preliminary investigations of previously unmapped ice-remnant forms in Eastern Hellas and the Deuteronilis/Protonilus/Nilosyrtis Mensae regions that we have found using the recently available Context Camera (CTX) image mosaic (http://murray-lab.caltech.edu/CTX/). These landforms are newly identified small components of the martian glacial system, that are different from, but likely related to, glacier-like forms and recessional glacier-like forms. We also search for the cirque signature of ice erosion on Mars, and discuss how the timing of glacial, deglacial, and paraglacial activity may be further constrained by evaluating the existence and distribution of all possible components of a glacial landsystem. Interpretations of Mars from remote sensing alone can be evaluated against targeted interpretations on Earth using both remote sensing and field studies. In particular we will share on recent work studying debris sources and glacier evolution at Mt. Rainier, Washington state. By applying terrestrial understanding to Mars we aim to evaluate how present-day martian landforms are informative of past activity and conditions during times when orbital parameters, climate, and water-ice distribution were different.
Land use regression modelling of ambient air pollutants in Hong Kong
Authors: Li Zhiyuan , Yim Steve Hung Lam , Ho Kin-Fai
Published: March 2020

Land use regression (LUR) models estimate air pollutant concentrations for areas without air quality measurements, which provides valuable information for exposure assessment and epidemiological studies. In the present study, we developed LUR models for ambient air pollutants in Hong Kong, China, a typical high-density and high-rise city. Air quality measurements at sixteen air quality monitoring stations, operated by the Hong Kong Environmental Protection Department, were collected. Moreover, five categories of predictor variables, including population distribution, traffic emissions, land use variables, urban/building morphology, and meteorological parameters, were employed to establish the LUR models of various air pollutants. Then the spatial distribution of air pollutant concentrations at 1 km × 1 km grid cells were plotted. Taking fine particle (PM2.5) as an example, the developed LUR model explained 89% of variability of PM2.5 concentrations, with a leave-one-out-cross-validation R2 of 0.64. LUR modelling results for other air pollutants will be presented. In addition, further improvements on the development of LUR models will be discussed. This study can help to assess long-term exposures to air pollutants for high-density and high-rise urban areas like Hong Kong.
Relationship between Thermodynamic Anomalies in Arabian Sea–Bay of Bangle on Rainy-season Precipitation in Yunnan
Authors: Zhu Yingmo
Published: March 2020

This study examines how the thermodynamic anomaly in Arabian Sea (AS)–Bay of Bangle (BOB) relates to Yunnan precipitation in the rainy season. The observational diagnosis basing on data sets of atmospheric circulation reanalysis, precipitation from 124 stations in Yunnan and outgoing longwave radiation indicates that, when the thermodynamic anomaly in the AS–BOB is weaker during rainy-season, an anomalous anticyclone will control the AS–BOB. An anomalous cyclone in Yunnan resulted from the anomalous anticyclone in the AS–BOB induces anomalous water vapor converging with anomalous cold air in the same region. As a result, heavier-than-normal precipitation occurs in Yunnan in rainy-season. When the thermodynamic anomaly in the AS–BOB is stronger, the opposite configuration of anomalous circulation will cause less-than-normal precipitation in Yunnan. The results of several numerical experiments obtained from a linear baroclinic model support the key physical processes revealed in the observational diagnosis.
Continuous observations of CO2, H2O and CH4 exchange in an East-African rangeland
Authors: Merbold Lutz , Dowling Thomas , Leitner Sonja , Wooster Martin , Vrieling Anton , Fava Francesco , Gluecks Ilona
Published: March 2020

Semi-arid rangelands, common across Sub-Saharan Africa (SSA), are under increased anthropogenic pressure by a growing population and the necessity to produce sufficient amounts of food and nutrition. Rangelands in SSA are characterized by nutrient-poor soils and distinct wet and dry season(s). Due to the soil and climate combination, conventional crop farming is often not feasible without additional inputs in terms of water and mineral fertilizer. Instead, livestock keeping constitutes a valuable option to use these marginal lands and has been practiced in SSA for centuries. As a result, livestock and wildlife jointly feed on these pastures, a trait that distinguishes these systems from most western rangelands, where large herbivore herds are the exception rather than the norm. To date a thorough, climate-smart assessment that includes continuous greenhouse gas (GHG) exchange measurements in combined wildlife-livestock systems has not been undertaken. Here we provide eddy covariance (EC) measurements of CO2/CH4/H2O from Kapiti Research Station in Kenya - a benchmark site for sustainable food production while also hosting wildlife. The GHG exchange measurements were complemented with wildlife camera traps to monitor both animal movement as well as plant phenology in the footprint of the EC tower. Our results show continuous CO2 uptake during the wet seasons with considerable CO2 emissions following distinct (>10mm) precipitation events after prolonged dry periods. Temporal dynamics of net ecosystem exchange of CO2 was strongly correlated with canopy greenness (green chromatic coordinate) derived from field camera imagery. Methane flux measurements were highly variable and were particularly related to the presence of wildlife and/or livestock in the fetch of the EC tower. Our data suggest that these rangeland systems are accumulating carbon and thus compensate the methane emissions from livestock.
Sorption model identification for chromium transport in unconsolidated sediments
Authors: Cao Yang , Dai Zhenxue , Zhang Xiaoying , Ma Ziqi
Published: March 2020

The adsorption of hexavalent chromium Cr(VI) onto six different natural unconsolidated sediments (two loamy sand, two sandy loam, loam, silty loam clay) was studied using batch and column experiments. Equilibrium adsorption capacities and kinetic rate were calibrated using batch experimental data. Elovich, pseudo first- and second-order models were used to fit the kinetic adsorption data, respectively. Henry’s, Freundlich, and Langmuir isotherms were used to fit the equilibrium adsorption data. Four model selection criteria, Akaike information criterion (AIC), modified Akaike information criterion (AICc), Bayesian information criterion (BIC), and Hannan information criterion (HIC) were used to discriminate kinetic and equilibrium models. These criteria suggest that the selected optimal model depends on the sediment type. Specifically, we studied effects of different factors including pH, solid/solution ratio, particle size, and clay mineral content on adsorption capacities. Column experiments were performed and a deterministic equilibrium model as well as a chemical non-equilibrium model were applied to fit the breakthrough curves. Results revealed a high retention of Cr(VI) in sandy loam, loam and silty loam clay, and a high mobility in loamy sand. It was found that particle size and clay minerals played an important role in adsorption process. The results from this study provide important insight for us to understand the transport behaviors of Cr(VI) in porous media.
Atmospheric mercury (Hg(0)) concentrations and Hg(0) fluxes in the Sea of Japan and the Okhotsk Sea in fall 2019
Authors: Lopatnikov Evgeny , Kalinchuk Viktor , Astakhov Anatoly , Gang Yang , Zou Jianjun
Published: March 2020

Continuous measurements of gaseous elemental mercury (Hg(0)) in the marine boundary layer (MBL) and Hg(0) fluxes were conducted in the Sea of Japan and the Sea of Okhotsk from September 7 to October 17, 2019. All Hg(0) measurements were carried out using two RA-915M mercury analysers (Lumex LLC, Russia). Hg(0) concentrations in the air were measured at two levels (about 2 m and 20 m above the sea surface) with a time resolution of 30 minutes. Hg(0) fluxes were measured at five sample stations using a dynamic flux chamber.

During the cruise Hg(0) concentrations varied in the range from 0,47 ng/m3 to 1,55 ng/m3, and from 0,31 ng/m3 to 2,71 ng/m3 with medians of 0,92 ng/m3 for 2 m and 20 m, respectively. Atmospheric Hg(0) concentrations in measurements sites were strongly depended on the regions from where air masses came to the study areas. As a result of the Concentration Weighted Trajectory (CWT) analysis we established 2 regions that influenced the Hg(0) concentrations during the cruise: the Northeast China with the Yellow Sea region and the Kurile Islands sector of the Pacific Ocean. The arrival of air masses from China and the Yellow Sea region caused an increase in Hg(0) concentrations in the air in the Sea of Japan and the Sea of Okhotsk. Elevated concentrations were also observed In the Sea of Okhotsk during the periods air masses came from the Kurile Islands sector of the Pacific Ocean.

Hg(0) fluxes were measured at 3 stations in the Sea of Japan and at 2 stations in the Sea of Okhotsk. The values ranged from 0,57 ng/m2/h to 1,55 ng/m2/h, with median value of 1,32 ng/m2/h. A positive relationships between Hg(0) flux and air and water temperature were observed.

This work was supported by the Russian Science Foundation (RSF) (Project № 19-77-10011) and by the National Natural Science Foundation of China (Projects №: 41876065, 41420104005, U1606401) and National Program on Global Change and Air-Sea Interaction (Project № GASI-GEOGE-04).
Pre-eruptive diffuse heating of volcanoes
Authors: Girona Társilo , Realmuto Vincent , Lundgren Paul
Published: March 2020

Identifying the observables that warn of volcanic unrest and impending eruptions is one of the greatest challenges in the management of natural disasters. An important but scarcely explored observable is diffuse heating, that is, the heat released passively through the ground. Diffuse heating represents one of the major energy sources in active volcanoes during inter-eruptive periods, and can dominate over the elastic energy released during seismic and deformation events. However, many questions remain open: Is there a direct correlation between diffuse heating and the subsurface processes that precede volcanic eruptions? To what extent are volcanic eruptions preceded by an enhancement of the diffuse emissions of heat? We address these questions by analyzing 16.5 years of long-wavelength (10.780 – 11.280 μm) thermal infrared radiance data recorded over nine volcanoes by the moderate-resolution imaging spectroradiometers (MODIS instruments) aboard NASA's Terra and Aqua satellites; this amounts to >35 TB of data and >210,000 MODIS scenes. Our statistical analysis reveals that volcanic edifices get warm for several years before magmatic, phreatic and hydrothermal eruptions. This pre-eruptive warming has been observed at Ontake (Japan), Ruapehu (New Zealand), Domuyo (Argentina), Calbuco (Chile), Redoubt and Okmok (Alaska), Pico do Fogo (Cape Verde), El Hierro (Spain), and Agung (Indonesia) volcanoes. In particular, we found pre-eruptive increases of up to ~1.5 K in the median temperature of the volcanic edifices; this, based on an energy balance, reflects increases of heat flux of up to 10 W/m2. We theorize that the pre-eruptive surface warming of volcanoes is the surface manifestation of shallow hydrothermal activity. Our retrospective analysis is especially relevant, since several of the eruptions analyzed did occur with little or no warning (e.g., the 2014 phreatic eruption of Ontake and the 2015 magmatic eruption of Calbuco). The possibility of tracking temporal changes of diffuse heating using satellite data opens new horizons to study the thermal reactivation of magma reservoirs and improve the forecasting of volcanic eruptions.
Evaluation of modelled methane emissions over high-latitude wetlands
Authors: Gao Yao , Burke Eleanor , Chadburn Sarah , Raivonen Maarit , Vesala Timo , Aurela Mika , Lohila Annalea , Yang Huiyi , Li Tingting , Aalto Tuula
Published: March 2020

Atmospheric emissions and concentrations of CH4 are continuing to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after CO2. Previous studies indicated that wetland CH4 emission is not only the single largest but also the most uncertain natural source in the global CH4 budget. Furthermore, the strong sensitivity of wetland CH4 emissions to environmental conditions has raised concerns on potential positive feedbacks to climate change. Therefore, evaluation of the process-based land surface models of earth system models (ESMs) in simulating CH4 emission over wetlands is needed for more precise future predictions. In this work, a set of high-latitude wetland sites with various nutrient conditions are studied. The wetland CH4 fluxes are simulated by the land surface model JULES of the UK Earth System model and the Helsinki peatland methane emission model (HIMMELI), which is developed at Finnish Meteorological Institute and Helsinki University. The differences between the modelled and observed CH4 fluxes are analyzed, complemented with key environmental variables for interpretation (e.g. soil temperature and moisture, vegetation types, snow depth, NPP, soil carbon). In general, the simulated CH4 fluxes by HIMMELI is closer to the observed CH4 fluxes in magnitude and seasonality at sites than those by JULES. The inter-annual variability of simulated CH4 fluxes by HIMMELI depends on the simulated anoxic soil respiration, which serves as the substrate of the CH4 fluxes in HIMMELI. The anoxic soil respiration is calculated based on the simulated soil respiration and water table depth in JULES. More accurate simulation of soil carbon pool and water table depth in JULES will lead to improvement in the simulated anoxic soil respiration.
Simulation of Rotational ground motion in the near field region
Authors: Stg Raghukanth , K singla Varun
Published: March 2020

 

In recent times, seismic rotational motions have received significant attention of seismologists as well earthquake engineers. The measurement of rotational motions is useful not only for the complete characterization of the ground motion, but also for estimating the additional risk to civil engineering structures posed by these motions. With the development of state-of-the-art instruments such as the ring-laser and fiber-optic gyroscopes, and mechanical and magneto-hydrodynamic devices, it is now possible to measure these motions over a large frequency bandwidth with accuracy. Nevertheless, nearly all earthquake-prone regions of the world lack the instrumentation to record these motions and the existing database of recorded rotational motions thus remains limited. In such situations analytical methods can provide estimates of rotational ground motions. It is thus common to simulate these motions and most analytical methods simulate rotations as curl of the displacement field. Because this relation (refer to as ‘curl-based’) is based on the ‘small deformations’ assumption, the ‘curl-based’ rotations are in a sense an approximation of the exact rotations, the latter being computed by using the rotational matrix directly extracted from the deformation gradient using the polar decomposition theorem. Despite this, no study has so far discussed the situations in which the ‘curl-based’ relation no longer holds. This paper therefore attempts to shed light on this issue by conducting two numerical studies. In the first study, a simple case of a point kinematic dislocation shear source buried in a homogeneous, elastic half-space is considered to get a qualitative idea about the combinations of the source and medium parameters that can lead to appreciable errors in the ‘curl-based’ rotations. The second study considers the finite-fault source model of Chi-Chi earthquake to illustrate these errors in a realistic scenario. Both these studies indicate that the ‘curl-based’ rotations can be in appreciable error when ‘exact’ rotations are in excess of  20 degrees and that this can happen in the near-field regions of surface-rupturing faults.
Spatial effects on extreme precipitation in the coastal areas of southeast China
Authors: Qian Weikang , Sun Xun
Published: March 2020

Extreme precipitation event, along with its secondary disasters, is one of the largest natural hazards leading to massive loss in human society. In the coastal areas of southeast china, tropical cyclones (TC) frequently visit the region with intensive precipitation in summer and autumn. Besides TC induced extreme precipitation, convectional precipitation is an alternative reason of extreme precipitation. This study investigated the spatial effects of the extreme precipitation during the raining season for both TC induced and non-TC induced extreme precipitation. The seasonal maximum daily precipitation data through 94 stations in southeast coastal areas of China from 1964 to 2013 were used. We developed a hierarchical Bayesian model with generalized extreme value distribution (GEV) to quantitatively assess the effects of spatial factors on the extreme precipitation. TC induced and non-TC induced extreme precipitation are modelled separately. It was found that the spatial factors that affect the TC induced and non-TC induced extreme precipitation are clearly different. For the TC induced extreme precipitation, the distance to the coastline has been found to be a significant spatial covariate that affects both the location and scale parameter of GEV across the whole areas, while spatial factors are diverse in different locations for non-TC induced extreme precipitation.
Magma ascent and eruption forecasting at Deception Island volcano (Antarctica) evidenced by δD and δ18O variations
Authors: Álvarez-Valero Antonio M. , Aulinas Meritxell , Geyer Adelina , Gisbert Guillem , Kereszturi Gabor , Núñez-Guerrero Elena , Polo-Sánchez Antonio , Sumino Hirochika
Published: March 2020

Geochemistry of volatiles in active volcanoes provides insights into the magmatic processes and evolution at depth, such as magma evolution and degassing, which can be implemented into volcanic hazards assessment. Deception Island is one of the most active volcanoes in Antarctica, with more than twenty explosive eruptions documented over the past two centuries. Hydrogen and oxygen isotopic variations in the volatiles trapped in the Deception Island rocks (glass and melt inclusions in phenocrysts) provide essential information on the mechanisms controlling the eruptive history in this volcanic suite. Thus, understanding the petrological and related isotopic variations in the island, has the potential to foresee the possible occurrence and its main eruptive features of a future eruption.

Information from hydrogen and oxygen stable isotopes combined with detailed petrologic data reveal in Deception Island (i) fast ascent and quenching of most magmas, preserving pre-eruptive magmatic signal of water contents and isotopic ratios, with local modification by rehydration due to glass exposition to seawater, meteoric and fumarolic waters; (ii) a plumbing system(s) currently dominated by closed-system degassing leading to explosive eruptions; (iii) control on the interactions of ascending magmas with the surface waters producing hydrovolcanic activity throughout the two main fault systems in Deception Island. These results can be considered in further studies of volcanic monitoring to improve the capability to interpret geophysical data and signals recorded during volcanic unrest episodes, and hence, forecast volcanic eruptions and related hazards.

This research was partially funded by the following projects: POSVOLDEC (CTM2016‐79617‐P) (AEI/FEDER‐UE), VOLGASDEC (PGC2018-095693-B-I00) (AEI/FEDER‐UE) and Programa Propio Ib-2019 (USAL). This research is also part of POLARCSIC activities.
Environmental seismology: Listening to landslides whispering
Authors: Chao Wei-An
Published: March 2020

The rapidly emerging field of Environmental Seismology (EnviroSeis) uses seismological techniques to monitor geomorphic processes at Earth’s surface, providing non-invasive, relatively inexpensive, continuous constraints on physical properties and dynamics of surface processes including landslides, debris flows, snow avalanches, river sediment transport, and variations in groundwater table. EnviroSeis has direct ties to real-time geohazards monitoring and provides timely warnings for the hazard mitigation and assessment. Nowadays, the places in world with real-time seismic networks are ready to implement EnviroSeis. The major topic focused on here is how to provide relevant information on the deep-seated landslides associated to the three-time stages:

Pre-slide: (1) seismic precursor and (2) seismic velocity changes corresponding to basal sliding behavior.

Sliding: A real-time landquake monitoring (RLMS; http://collab.cv.nctu.edu.tw/main.html)

After-slide: (1) near-real-time monitoring of river sediment transport and (2) early warning of the landslide-generated tsunami.
Observation on change of physico-chemical properties of crystalline rocks caused by freezing-thawing experiment
Authors: Choi Junghae
Published: March 2020

Groundwater and surface water may be contaminated by a range of soluble chemical compounds in regions where rocks are weathered by freeze–thaw cycles. To reduce this type of pollution, which is particularly common in mining areas, the effects of freeze–thaw weathering need to be investigated to help determine how the rock is weathered and what chemical compounds result from the weathering. The physical conditions of a rock’s surface generally change during freeze–thaw cycles, and voids on weathered surfaces tend to increase in number because of chemical dissolution of the minerals in the rock.

 

In this study, freeze–thaw experiments were performed using rock samples taken from near a mine. The physical changes in equally sized rock samples were observed during the experiment. To understand how chemical compounds were released during freeze–thaw cycles, powdered rock samples were added to distilled water and the chemical characteristics of the distilled water were determined. Information on physical changes in rocks can be used to understand how weathering affects the stability of cut slopes or tunnels, while the data from chemical analysis provide insights into the release of chemical species that can affect the surrounding natural environment.

 

We used physical and chemical (e.g. inductively coupled plasma–mass spectrometry) analysis methods to observe how the physical properties of the rocks and the chemical forms in a solution changed during a freeze–thaw experiment. The results show that the porosity and the dry density of the rock samples changed slightly during the experiment. The electrical conductivity and concentrations of chemical forms varied as the freeze–thaw cycle progressed. This study shows that weathering can be enhanced during freeze–thaw cycles and that groundwater is easily contaminated by the dissolved chemicals produced during this weathering.
Variability and trends of intense precipitation in a metropolitan area in the southern Brazil
Authors: Allasia Daniel , Petry Ingrid , Basso Raviel , Tassi Rutineia , Minetto Bruna
Published: March 2020

With the increase in the global population observed since the 20th century, urban centers are becoming more prominent, and its dynamic is now far from the natural. The impact of urbanization on the rainfall has been noticed since 1921 when Horton observed that cities with more than 100,000 inhabitants created favorable conditions for convective precipitation. Later, Huff and Changnon (1972) estimated an increase of 6 to 15% on average rainfall during the summer in these regions. Several other studies confirmed the trend and pointed out that on a small and medium scale, precipitation change is usually justified by the effect of heat islands. To understand these changes, high-resolution precipitation data is needed; however, due to the lack of monitored data, especially on the largest cities in the developing countries, new sources of information should be used. MSWEP is a three hourly gridded precipitation dataset, with 0.1º spatial resolution that combines data from gauges, satellite, and reanalysis-based data to provide precipitation estimates over the entire globe (Beck, 2019). In this study, MSWEP precipitation was used in order to observe the variability of intense precipitation over the Metropolitan Area of Porto Alegre in Southern Brazil, where some previous studies indicated urban effects on precipitation. Statistical analysis was performed to evaluate changes in the intense precipitation throughout the decades. The results show that the spatial distribution patterns of intense precipitation are maintained; however, in all statistics, it was possible to observe an increase in intense precipitation over the decades, that follows the increase of the urbanized area over time.
Hyper-resolution land surface modeling enables 30-m SMAP-based soil moisture at continental scales
Authors: Vergopolan Noemi , Chaney Nathaniel W. , Beck Hylke E. , Pan Ming , Sheffield Justin , Wood Eric F.
Published: March 2020

Accurate and detailed soil moisture information is essential for, among other things, irrigation, drought and flood prediction, water resources management, and field-scale (i.e., tens of m) decision making. Microwave-based satellite remote sensing offers unique opportunities for the large-scale monitoring of soil moisture at frequent temporal intervals. However, the utility of these satellite products is limited by the large footprint of the microwave sensors. Several downscaling techniques based on high-resolution remotely sensed data proxies have been proposed (1 km to 100 m). Although these techniques yield aesthetically pleasing maps, by neglecting how the water and energy fluxes physically interact with the landscape, these approaches often fail to provide soil moisture estimates that are hydrologically consistent.

This work introduces a state-of-the-art framework that combines a process-based hyper-resolution land surface model (LSM), a radiative transfer model (RTM), and a Bayesian scheme to merge and downscale coarse resolution brightness temperature to a 30-m spatial resolution. The framework is based on HydroBlocks, an LSM that solves the field-scale spatial heterogeneity of land surface processes through interacting hydrologic response units (HRUs). We demonstrate this framework by coupling HydroBlocks with the Tau-Omega RTM used in the Soil Moisture Active Passive (SMAP) mission and subsequently merging the HydroBlocks-RTM and the SMAP L3-enhanced brightness temperature at the HRU scale. This allows for hydrologically consistent SMAP-based soil moisture retrievals at an unprecedented 30-m spatial resolution over continental domains. 

We applied this framework to obtain 30-m SMAP-based soil moisture retrievals over the contiguous United States (2015-2018). When evaluated against sparse and dense in-situ soil moisture networks, the 30-m soil moisture retrievals showed substantial improvements in performance at field and watershed scales, outperforming both the SMAP L3-enhanced and the SMAP L4 soil moisture products. This work leads the way towards hydrologically consistent field-scale soil moisture retrievals and highlights the value of hyper-resolution modeling to bridge the gap between coarse-scale satellite retrievals and field-scale hydrological applications. 
Crop dispersal along the prehistoric highland silk road on the Tibetan Plateau
Authors: Yang Jishuai , Yang Xiaoyan
Published: March 2020

Previous studies demonstrated that the farmers spread into the Tibetan Plateau (TP) and permenantly settled there around 3600 yr cal BP, taking the ways on the northeastern edges of the TP and bearing the western crops of barley, and sheep. But, other studies argued the earlier permenant settlements or different ways to spread into the central TP. Meanwhile, the Yarlung Tsangpo River regions in southern TP, are considered to be one of the important routes for culture dispersal and human migration, jointing Tibetan Empire, Tang Dynasty and states in South Asia in history period, were proposed as highland silk road. However, the role of this route in prehistorical culture exchange and human colonization on the TP remains unclear, due to the scarce of archaeological work in these regions.

Systematic surveys along the Yarlung Tsangpo River regions had carried out in last two years. Charcoals and charred seeds were floated from the cultural layers in 31 sites and 60 new carbon-14 dates had been got. Charred seeds include wheat, barley and pea from the west, and broomcorn millet and foxtail millet from the east. In combination with previous published dates, we set up routes of crop dispersal and brief history of human activities on the central TP. Neolithic people had occupied the Yarlung Tsangpo Valley from the different direction of the TP in the third millennium BC with different western crops or eastern crops, and moved along the River and its tributaries. The route for dispersal is similar with the historic highland silk road, indicating this road had played a important role since prehistory.
What do we gain from cruise-based teaching in marine science university education?
Authors: Renner Angelika , Wiedmann Ingrid
Published: March 2020

Scientific teaching cruises are a popular part of marine science courses in undergraduate and graduate education, but cruise time is under severe pressure due to financial and logistical constraints. In this study, we investigate the role of ship-based fieldwork in facilitating student learning in marine science education. In particular, we explore the contributions of different course components, such as lectures, seminars, and laboratory exercises, towards student learning in two undergraduate and one graduate course. Results from an online survey and interviews with students, teachers, and teaching assistants suggest that undergraduate students tend to learn most during the lectures and the cruise. Conversely, graduate students appear to learn most when conducting ship-based experiments and during the preparation of the cruise report. While the teaching cruise is probably a course component that is less focussed on transfer of knowledge in forms of facts and theories than e.g., lectures and seminars, they are effective for students to consolidate and to learn to apply their knowledge. In addition, the teaching cruise contributes considerably towards the development of practical and soft skills, such as group management and communication, which are highly valued by potential future employers. We therefore argue that teaching cruises provide a valuable teaching platform that goes beyond the mere dissemination of scientific content and train students in skills applicable to any future career.
New geological and paleomagnetic data from Siberian Craton and implications for the post 2 Ga global paleogeography
Authors: Pisarevsky Sergei , Donskaya Tatiana , Gladkochub Dmitry
Published: March 2020

Siberian Craton is generally recognised as one of the building blocks of two supercontinents: Mesoproterozoic Nuna (Columbia) and Neoproterozoic Rodinia. Although the exact Siberian positions in Nuna and Rodinia are debated, most workers agree that the southern part of Siberia (hereafter in present day coordinates) has been located not too far from the northern margin of Laurentia (cratonic part of North America) between ca. 1600 Ma and ca. 700 Ma. New geochronological, paleomagnetic and geochemical data from the Siberian craton obtained in recent years improved our understanding of Siberian geological history comparing to previous reviews. The progress in global Precambrian paleogeography also contributed to a re-evaluation of the Siberian tectonic history. The compilation of Siberian paleomagnetic data suggests that after the final assembly of Siberian Craton and until Ediacaran time the craton mostly occupied the low- to moderate latitudes. Most of this time western, northern and eastern Siberian edges have been passive or active oceanic margins. The southern margin Siberian margin has been probably connected with some other continent. Using new geological and paleomagnetic data, in particular recent results of the detrital zircons distributions in Siberia, Laurentia and other ancient continents, we tested several paleogeographic reconstructions of this connection. We also propose a new model of the breakup of Siberia from the remnants of Rodinia and consequent opening of the Paleo-Asian Ocean.
Assessment of the potential for irrigation development in Albert Nile basin: A case study of Nebbi district
Authors: Kiggundu Nicholas , Bwire Charles , Wanyama Joshua
Published: March 2020

There has been limited research conducted on irrigation potential in Uganda. The existing studies provide a wide number of estimates of irrigation potential for Uganda and thus constrain reliable medium term planning and investment in the subsector. This research was aimed at assessing the potential for irrigation development in Nebbi District, which cover 195,300 km2, with a view of guiding planning and strategic investment in irrigation. Irrigation potential was assessed as an aggregation of the land suitability, water requirement and the available water for irrigation for three systems (drip, sprinkler and surface). Land suitability evaluation for the three systems was determined based upon topography and soil characteristics. The FAO CROPWAT model was used to determine the water requirements for the selected crops. Water resources assessment was carried out using rainfall data and the stream flow analysis of the available water resources in the study area. For surface irrigation, no area was classified as highly suitable or moderately suitable. Only 0.03% (48.91 ha) is marginally suitable, 36% (68,445.55 ha) currently not suitable whereas 64% (121,606.33 ha) permanently not suitable. For drip irrigation, 58.7% (111,591 ha) is marginally suitable and 25.8% (49,084 ha) is moderately suitable. Furthermore, 15% (28,492 ha) and 0.5% (989 ha) are currently not suitable and permanently not suitable respectively. There was no area classified as highly suitable under drip irrigation. For sprinkler irrigation, 14.1% (26 815.8 ha) of the area is marginally suitable and 0.03% (48.1 ha) is classified as moderately suitable for sprinkler irrigation. 47.5% (90 291.4 ha) and 38.4 % (72 987.2 ha) of the area is currently not suitable and permanently not suitable respectively. The mean capability index (Ci) for surface irrigation was 36.1 (currently not suitable), 45.4 (marginally suitable) for drip irrigation while sprinkler irrigation Ci was 42.8 (marginally suitable). Crop evapotranspiration (ETc) for the selected crops (tomatoes, cabbages and onions) varied from 2.46 to 5.76 mm/day; 2.87 to 5.92 mm/day and 2.87 to 4.78 mm/day respectively. The results from water resources assessment revealed that the total catchment yield was 2.69 x 109 m3 which permits irrigation for an area of 141,817.65 ha. The results showed that drip irrigation system was more suitable for the Nebbi district.
Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica
Authors: Turney Christian , Fogwill Christopher , Golledge Nicholas ,   The AntarcticScience.com Team
Published: March 2020

The future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG; 129-116 kyr), which experienced warmer polar temperatures and higher global mean sea level (GMSL +6 to 9 m) relative to present day. LIG sea level cannot be fully explained by Greenland Ice Sheet melt (~2 m), ocean thermal expansion and melting mountain glaciers (~1 m), suggesting substantial Antarctic mass loss was initiated by warming of Southern Ocean waters, resulting from a weakening Atlantic Meridional Overturning Circulation in response to North Atlantic surface freshening.  Here we report a blue-ice record of ice-sheet and environmental change from the Weddell Sea Embayment at the periphery of the marine-based West Antarctic Ice Sheet (WAIS) which is underlain by major methane hydrate reserves. Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide the first evidence for substantial mass loss across the Weddell Sea Embayment during the Last Interglacial, most likely driven by ocean warming and associated with destabilization of sub-glacial hydrates. Ice-sheet modelling supports this interpretation and suggests that millennial-scale warming of the Southern Ocean could have triggered a multi-meter rise in global sea levels. Our data indicate that Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice-climate feedbacks that further amplify warming.
First Cenozoic ages from the Roraima’s region landscape (Northern Brazil): insights from hematite and goethite (U-Th)/He dating
Authors: Sanchez Caroline , Gautheron Cécile , Pinna-Jamme Rosella , Haurine Frédéric , Roig Jean-Yves , Coueffë Renaud
Published: March 2020

Lateritic peofiles results from weathering processes involving coeval warm temperature and high precipitation seasons rates in intertropical context. Through geological times, the laterite will develop and an indurated duricrust iron oxide enriched horizon may develop on the profile top. The duricrusts can be used as excellent lateritic surface markers, that can be preserved from erosion. Nevertheless, the relationship between the timing of their development, the geomorphology and the processes involved are still debated.

To this end, we have investigated duricrusts of the large Roraima plateau, in the Guyana shield, Northern Brazil, attributed to the “Gondwana” surface of purported “Jurassic-Cretaceous” age. Four duricrust samples have been collected from ~840 to 950 m.a.s.l in the same area, with both 1.9 Ga sandstone and 1.75 Ga gabbro as parent rock respectively. The duricrust samples exhibit different textures, including pisoliths and massive banded type textures.

Samples mineralogy have been characterized using classical methods such as optical properties, texture and DRX. Several generations have been finally identified. The SEM analysis revealed different porosities and microstructures. Each identified generation collected has been dated by the (U-Th)/He method using micrometric aliquots.

All the samples present quite homogenous dated generations, presenting mostly Paleocene/Eocene as well as early and late Miocene ages. In addition, oldest identified generations in the pisolithic sample suggest remaining of older Cretaceous weathering event. Our geochronological results are not directly correlated to the sample altitudes but more likely to the duricrust structure. Finally, the (U-Th)/He age distribution reveal that the Roraima landscape underwent several weathering episodes in the Cenozoic times and are younger than initially supposed.
Are Fungus-Growing Termites Major Contributors To Sediment Grain-Size Distributions In Subtropical Environments?
Authors: Van Thuyne John
Published: March 2020
Detection of Plastic Strain Using GNSS Data of Pre- and Post-Seismic Deformation of the 2011 Tohoku-oki Earthquake
Authors: Fukahata Yukitoshi , Meneses-Gutierrez Angela , Sagiya Takeshi
Published: March 2020

In general, there are three mechanisms causing crustal deformation: elastic, viscous, and plastic deformation. The separation of observed crustal deformation to each component has been a challenging problem. Meneses-Gutierrez and Sagiya (2016, EPSL) have successfully separated inelastic deformation from observed geodetic data from the comparison of GNSS data before and after the 2011 Tohoku-oki earthquake in the northern Niigata-Kobe tectonic zone (NKTZ), central Japan. In this study, we further succeed in separating plastic deformation as well as viscous deformation in the northern NKTZ using GNSS data before and after the 2011 Tohoku-oki earthquake, under the assumptions that elastic deformation is principally caused by the plate coupling along the Japan trench and that plastic deformation ceased after the Tohoku-oki earthquake due to the stress drop caused by the earthquake. The cease of plastic deformation can be understood with the concept of stress shadow used in the field of seismic activity. The separated strain rates are about 30 nanostrain/yr both for the plastic deformation in the preseismic period and for the viscous deformation in both the pre- and post-seismic periods, which means that the inelastic strain rate in the northern NKTZ is about 60 and 30 nanostrain/yr in the pre- and post-seismic periods, respectively. This result requires the revision of the strain rate paradox in Japan. The strain rate was exceptionally faster before the Tohoku-oki earthquake due to the effect of plastic strain, and the discrepancy between the geodetic and geologic strain rates is much smaller in usual time, when the plastic strain is off. In oder to understand the onset timing of plastic deformation, the information on stress history is essentially important.

 