bluuebunny/crossref_metadata_2025 huggingface dataset:
Poroelasticity and self-stimulation around geothermal producers in quadruplet versus triplet configurations
Authors: Adu Ntow Derrick , Ghergut Julia , Sauter Martin , Wagner Bianca , Wiegand Bettina , Yamah Mohammed
Published: March 2020

At the real-world site underlying the scoping simulation example, adding a fourth well (second producer) is being endeavored in order to maximize the benefit from an unexpectedly high injectivity at the already existing two injectors, whereas the modest productivity of the existing producer is acting as the turnover-limiting factor in the currently operating triplet. Up-sizing to a quadruplet configuration (two producers instead of one) might thus also, by virtue of competing pressure diffusion and poroelastic effects, improve the productivity of the first producer, so to say as an ‘added bonus’ for up-sizing. In the currently operating triplet regime, injectivity also appears to increase with operation time i. e. with the cumulative volume of fluid turnover, this being attributed to (thermo-)hydrogeochemical rather than hydraulic-poroelastic effects. Scoping poroelastic simulations are complemented by a comparison of fluid residence time distributions and thermal lifetime expectations between the two (quadruplet versus triplet) configurations.
Mapping soil formation in Lithuania. A national-scale analysis.
Authors: Pereira Paulo , Brevik Eric , Inacio Miguel , Kalinauskas Marius , Miksa Katarzyna , Gomes Eduardo
Published: March 2020

Soil formation is vital for the existence of life. Soil provides a wide range of direct and indirect ecosystem services (ES) such as carbon sequestration, water and flood regulation, food provisioning, raw material culture, and heritage. Soil formation is complex and depends on the parent material, climate, topography, biological activity, and time. This intricate process is strongly affected by human activities (e.g., agriculture, urbanization) that generally result in a degradation process. Mapping soil formation is challenging due to a large number of variables involved and the complexity of their interaction. The objective of this work is to map soil formation in Lithuania. Several variables were selected to assess soil formation such as lithology, time (glacial retreat), slope, topographic wetness index, roughness, slope length, soil mineralogy, depth, texture, available water capacity, pH, organic carbon, nitrogen, potassium, phosphorous, January average temperature, June average temperature, annual average precipitation, and land use. To validate the model, we used soil cation exchange capacity. The variables were ranked according to the least to the most favorable conditions. The weight of the variables was assessed using the Analytic Hierarchical Process and ranked by 20 international experts on the soil. The results of the model are acceptable (r2=0.48), owing to the complexity involved in soil formation.

This work was funded from the European Social Fund project LINESAM No. 09.3.3-LMT-K-712-01-0104 under grant agreement with the Research Council of Lithuania (LMTLT).
Propagation factors influencing observations of resonances of atmospheric gravity waves
Authors: Zabotin Nikolay , Godin Oleg
Published: March 2020

Observations of the ionosphere with the airglow, GPS-TEC, and HF radar techniques reveal a resonance-kind response of the middle and upper atmosphere to broad-band excitation by earthquakes, volcano eruptions, and convective storms. The resonances occur at such frequencies that an atmospheric wave, which is radiated at the ground level and is reflected from a turning point in the middle or upper atmosphere, upon return to the ground level satisfies boundary conditions on the ground. The "buoyancy" resonances (resonances of atmospheric gravity waves) with periods from several minutes and up to several hours arise in addition to well-known "acoustic" resonances with periods of about 3–4 minutes. The buoyancy resonances occur on the gravity branch of the dispersion relation for the acoustic-gravity waves. Infragravity waves in the ocean covering the same frequency band may serve as an efficient source of excitation of the buoyancy resonances. We have obtained dispersion relations for buoyancy resonances earlier. In this paper we investigate the influence of specific propagation characteristics of the gravity waves (their oblique propagation and dissipative attenuation) on conditions of their observation. We use  asymptotic (WKB and ray tracing) methods to investigate relationship between the gravity wave skip distance and the dimensions of typical infragravity wave packets in the oceans and find that conditions can be met for interaction of the same atmospheric wave packet with the same ocean wave packet. The dissipative attenuation eliminates some of the resonance modes, but still many of them remain intact. We use numerical solutions of the full wave equation to confirm results obtained by asymptotic methods. Calculations of this kind demonstrate a possibility of resonance-like behavior of the gravity waves in situations when partial reflections (caused by extrema of the refractive index) appear in addition to the total reflection. Unlike acoustic resonances, buoyancy resonances exhibit high sensitivity to the wind velocity profile and its variations. Non-stationarity of the atmosphere is an important factor limiting possibilities to observe the buoyancy resonances. Nevertheless, relatively low threshold for meeting all other conditions for their appearance and temporal/geographical diversity of the atmosphere makes it still quite probable to see their manifestations. The resonances correspond to most efficient coupling between the atmosphere and its lower boundary and are promising for detection of such coupling.
Removal of caffeine by oxidized biochar
Authors: Anastopoulos Ioannis , Pashalidis Ioannis , Robalds Artis
Published: March 2020

Oxidized biochar from plant biomass (OBPM) was used to remove caffeine (CF) from aqueous solutions. Among examined parameters that affect adsorption, pH was found to play the most important role. By increasing the initial pH from 2 to 4, the adsorption capacity of CF was increased, whereas for pH above 4, a decline of the adsorption efficiency was noticed. The effect of contact time was also investigated in the range of 1 – 150 minutes and results indicated that the adsorption process consists of two steps. The initial step was relatively fast most probably, because a large number of adsorption surface sites was available, and with proceeding contact time the adsorption rate declined. The latter could be attributed to the decreasing number of vacant sites and to the development of repulsive forces between the free CF molecules and the occupied OBPM surface. The experimental data were best fitted by the pseudo-second order kinetic, compared to pseudo-first order kinetic model and the Freundlich isotherm model better fitted the data. The raise of temperature from 25 to 50 °C affected negatively the CF removal, indicating the exothermicity of the adsorption. Finally, FTIR spectroscopic data and investigations on the effect of ionic strength indicated that the adsorption mechanism is mainly based on electrostatic interactions and the formation of outer sphere surface complexes.

 
The relationship between intraseasonal precipitation of Iran and combined effects of MJO and NAO
Authors: Pourasghar Farnaz , Babaiean Iman , Ghaemi Hooshang
Published: March 2020

Because of low precipitation and its severe fluctuations in Iran, understanding the dynamics of large scale climate modes and probability of annual and intraseasonal precipitation variation is essential for water management. This study investigates the characteristics of the combined effects of Madden-Julian Oscillation (MJO) and North Atlantic Oscillation (NAO) on precipitation over Iran. Daily precipitation and atmospheric data (relative humidity and vertical velocity) were analysed over Iran during wet season (October to May) for the period 1961 to 2018. The results indicated that: 1) Distinct difference can be observed in spatial distribution of the probability of daily precipitation above upper tercile for MJO phases, phase 1 and 2 wetter while 4 and 5 are drier. The relative humidity is higher in phases (1-3 and 7-8) and lower in phases (4-6). The vertical velocity shows upward (downword) motion in phases 1-2 and 7-8 (3-6). 2) Response of rainy season precipitation over Iran to MJO is more affected by the large-scale atmospheric variation associated with negative NAO as compared to positive NAO. In the negative NAO, the MJO increase (decrease) the probability of upper tercile precipitation 1.2 (0.7) times in phases 2-3 (4-6) and significant tests show a significantly large response for west and North west of Iran. In contrast of positive NAO, the relative humidity and vertical velocity is more affected by negative NAO state. The more (less) humidity and upward (downward) motions increase (decrease) precipitation in phases 2-3 (4-6).
Assessment of potential ecological risk due to hydrological flow regime modification in the Hanjiang River basin 1950-2017
Authors: Yu Meixiu , Wood Paul , Liu Xiaolong , Li Qiongfang
Published: March 2020

River regulation by the construction of reservoirs represents one of the greatest challenges to the natural hydrological regime and ecological health of riverine systems. The Danjiangkou (DJK) Reservoir is the largest reservoir on the Hangjiang River and started operation in 1967 and was upgraded in 2012 to provide water resource for the South-North water transfer project through central China. However, the effect of the reservoir operation on the downstream hydrological regime and ecological health of the Hanjiang River after the upgrade (increase in dam wall height) has not been examined thus far. The daily discharge series from four stations along the main stem of the Hanjiang River, including a control site were examined from 1950-2017.  the study period was divided into three periods based on the different stages of the reservoir operation: i)1950-1966, ii) 1967-2012 and iii) 2012-2017. The nature of the hydrological alteration and the ecological risk of diversity (Shannon diversity index) during different periods were investigated. The result clearly indicate that the DJK reservoir has significantly modified the hydrological regime in the middle and downstream section of the Hanjiang River, with most significant modifications recorded immediately downstream of the reservoir. Using the Range of Variability Approach, after the increase of reservoir capacity at Huangjiagang the river ecological flow requirements could not be fully guaranteed and the frequency and intensity of ecodeficit increased. Biodiversity downstream of the dam was significantly reduced at Huangjiagang (Huangzhuang) and there was an increased risk of ecosystem degradation during both the second and third time period.
Multiband (X, C, L) radar amplitude analysis for a mixed sand- and gravel-bed river in the eastern central Andes
Authors: Purinton Benjamin , Bookhagen Bodo
Published: March 2020

Synthetic Aperture Radar (SAR) amplitude measurements from spaceborne sensors are sensitive to surface roughness conditions near their radar wavelength. These data can be exploited to measure gravel-to-sand transitions and downstream gradients in grain size related to geomorphic setting in tectonically active high mountain environments at large spatial scales. The bedload of mixed sand- and gravel-bed rivers can be considered mixed smooth (compacted sand) and rough (gravel) surfaces. Here, we assess backscatter gradients over a large high-mountain alluvial river with aerially exposed sand and gravel bedload using X-band TerraSAR-X/TanDEM-X, C-band Sentinel-1, and L-band ALOS-2 PALSAR-2 radar scenes. In a first step, we compare backscatter response over vegetation-free endmember surfaces within the dry channel bed to assess expected responses and limitations of SAR roughness measurements. We then develop methods to extract smoothed backscatter gradients downstream along the channel using kernel density estimates. In a final step, the presence of sand and gravel bars is analyzed using Fourier frequency analysis, by fitting stretched exponential and power-law models to the power spectrum. We find a large range in backscatter depending on the heterogeneity of contiguous smooth- and rough-patches of bedload material. The SAR signal responds primarily to the fraction of smooth-sand bedload, but is further modified by gravel elements. The sensitivity to gravel is more apparent in longer wavelength (L-band) radar. Because the spatial extent of smooth sand bars is typically < 50 m, only higher resolution sensors (e.g., TerraSAR-X/TanDEM-X) are useful for power spectrum analysis. Our results show the potential for mapping sand-gravel transitions and local geomorphic complexity using SAR amplitude at the scale of large high mountain catchments with aerially exposed bedload.
Detecting risk of regime shifts in ecosystems
Authors: Rocha Juan
Published: March 2020

Ecosystems around the world are at riks of critical transitions due to increasing anthropogenic preasures and climate change. However, it is not clear where the risks are higher, or where ecosystems are more vulnerable. When a dynamic system is close to a threshold, it leaves a statistical signature on its time series known as critical slowing down. It takes longer to recover after a small disturbance, which translates into increases in variance, autocorrelation, and skewness or flickering. Here I measure critical slowing down on primary production proxies for marine and terrestrial ecosystems globally. Slowness is an indicator of potential instabilities and a proxy of resilience. While slowness is not a universal indicator for critical transitions, it can be used for detection of potential regime shifts.
The changing nature of particulate organic carbon and the relation to aerosol liquid water
Authors: Carlton Annmarie , Christiansen Amy , Porter William , Flesch Madison
Published: March 2020

Particulate organic carbon (OC) mass concentrations demonstrate decreasing trends in many regions across the contiguous US (CONUS). We investigate decadal trends in specific total organic carbon (TOC) volatility fractions OC1, OC2, OC3, and OC4 as defined and reported at 121 locations in the Interagency Monitoring of PROtected Visual Environments (IMPROVE) monitoring network from 2005-2016 for 23 chemical climatology regions across the CONUS. Volatility fraction OC2 drives ubiquitous decadal decreases in TOC, and OC3 mass concentrations increase. The largest changes in OC2 and OC3 occur in the eastern US. In four focus regions (Northeast, Appalachia, West Texas, and Northwest), OC fraction mass concentrations are converted to organic mass (OM) using region-specific OM:OC ratios. GEOS-Chem simulations reproduce and correlate strongly (R2>0.7) with OM fraction decadal trends. Decreases in aerosol liquid water (ALW) concentrations are tightly linked to observed change in individual TOC thermal fractions, and aerosol products derived from aqueous-phase isoprene oxidation predicted by GEOS-Chem. These results lend insight to changing chemical regimes with implications for particle phase state, viscosity, and oxidation state.
CALIOP PSC observations from 2006-2019
Authors: Pitts Michael , Poole Lamont
Published: March 2020

Even though the role of polar stratospheric clouds (PSCs) in stratospheric ozone depletion is well established, important questions remain unanswered that have limited our understanding of PSC processes and how to accurately represent them in global models.  This has called into question our prognostic capabilities for future ozone loss in a changing climate.  A more complete picture of PSC processes on polar vortex-wide scales has emerged from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instrument on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite that has been observing PSCs at latitudes up to 82 degrees in both hemispheres since June 2006.  In this paper, we present a state-of-the-art climatology of PSC spatial and temporal distributions and particle composition constructed from the more than 14-year CALIOP spaceborne lidar dataset.  The climatology also includes estimates of particulate surface area density and volume density to facilitate comparisons with in situ data and measurements by other remote sensors, as well as with theoretical models relating PSCs to heterogeneous chemical processing and ozone loss. Finally, we compare the CALIOP PSC data record with the 1979-1989 SAM II (Stratospheric Aerosol Measurement II) solar occultation PSC record to investigate possible multi-decadal changes in PSC occurrence.
Linking tree rings with satellite observations of soil moisture: toward the reconstruction of water availability in the Mediterranean Andes region
Authors: Gonzalez-Reyes Alvaro , Christie Duncan , LeQuesne Carlos , Rojas-Badilla Moises , Muñoz Tomas , Muñoz Ariel
Published: March 2020

Soil moisture is a key variable into the earth surface dynamics, however long-term in situ measurements are globally scarce. In the Mediterranean Andes of Chile (30° - 37°S) grow the long-lived conifer “Ciprés de la Cordillera” (Austrocedrus chilensis), which is a demonstrated hydroclimatic proxy capable to cover the last millennium. Previous paleoclimatic studies have documented a high sensitivity between tree species and several hydroclimatic variables such as precipitation, streamflow, snowpack and aridity indexes, but the lack of in situ soil moisture observations has precluded an assessment of the spatial growth responses to high-resolution soil moisture variability. Here, we use three A. chilensis chronologies to determine linkages with the satellite-based surface soil moisture product v04.5 generated by ESA. We found significant relationships between tree-growth an a soil moisture field across the 32° - 34°S spatial domain of western South America from January to September during 1985 – 2013 period (r = 0.65; P < 0.001). Temporal relationships between tree-growth and soil moisture satellite observations exhibit a significant spectral coherence associated to cycles around 7 years (P < 0.10) and a clear decadal variability. Based on our preliminary results and the present extensive network of A. chilensis tree-ring chronologies, this species appears as a promising proxy to reconstruct surface soil moisture variability derived from remote sensing over the last millennium in a topographically complex Andean region of South America.

Acknowledgements

Alvaro Gonzalez-Reyes wish to thank: CONICYT+PAI+CONVOCATORIA NACIONAL SUBVENCIÓN A INSTALACIÓN EN LA ACADEMIA CONVOCATORIA AÑO 2019 + PAI77190101
How and why has extreme hourly precipitation changed in the major urban agglomerations over China?
Authors: Luo Yali , Furtado Kalli , Gordon Hamish
Published: March 2020

Understanding changes in sub-daily precipitation extremes and its attribution is critical for urban planners to build more sustainable and reliant cities. Three major urban agglomerations have been formed in China as a result from fast economic development since about the early-1990s, namely, the Pearl River Delta (PRD) in coastal South China, the Yangtze River Delta (YRD) in coastal East China, and the Beijing-Tianjin-Hebei (BTH) region in northern China. In this study, the hourly precipitation data in 1971-2018 from national weather stations are combined with historical land-use change data to investigate changes in extreme hourly precipitation (EXHP) in the three regions. Also, a large ensemble of extreme rainfall events (EXREs) during 2011-18 are analyzed using observations collected by densely-distributed automatic weather stations and radar network combined with reanalysis data. The results suggest that the strong urban heat island (UHI) effect in these urban agglomerations is conducive to intensification of hourly precipitation. However, statistically insignificant changes in EXHP are observed over the BTH region. In contrast, significantly increasing frequency of EXHP occur over the other two coastal urbanized regions, with some distinct features in the evolution of EXHP-producing storms and the relevant synoptic situations between the two regions. The individual and combined effects of land-cover and land-use (LCLU) change and increasing anthropogenic aerosol emission are investigated by use of an integrated modeling approach. An ensemble of convection-permitting simulations is performed, combining two LCLU and aerosol emission scenarios. The influences of these two factors are discussed based on the simulations.
Diverse influences of spring Arctic Oscillation on the following winter El Niño-Southern Oscillation in CMIP5 models
Authors: Zheng Yuqiong
Published: March 2020

This study evaluates the ability of 35 climate models, which participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5) historical climate simulations, in reproducing the connection between boreal spring Arctic Oscillation (AO) and its following winter El Niño-Southern Oscillation (ENSO). The spring AO-winter ENSO correlations range from -0.41 to 0.44 among the 35 models for the period of 1958-2005. Ensemble means of the models with significant positive and negative AO-ENSO correlations both show strong spring sea surface temperature (SST) cooling in the subtropical North Pacific during a positive phase of spring AO, which is conducive to occurrence of a La Niña event in the following winter. However, the models with positive AO-ENSO relations produce a pronounced spring cyclonic anomaly over the subtropical northwestern Pacific and westerly anomalies over the tropical western Pacific (TWP). These westerly wind anomalies would lead to SST warming and positive precipitation anomalies in the tropical central-eastern Pacific (TCEP) during the following summer, which could maintain and develop into an El Niño-like pattern in the following winter via a positive air-sea feedback. By contrast, the models with negative AO-ENSO connections fail to reproduce the spring AO-related cyclonic anomaly over the subtropical northwestern Pacific and westerly wind anomalies in the TWP. Thus, these models would produce a La Niña-like pattern in the subsequent winter. Difference in the spring AO-associated atmospheric anomalies over the subtropical North Pacific among the CMIP5 models may be attributed to biases of the models in simulating the spring climatological storm track.
Artificial intelligence for discrimination of sediment facies based on high-resolution elemental and colour data from coastal sediments of the East Frisian Wadden Sea, Germany
Authors: Lee An-Sheng , Enters Dirk , Liou Sofia Ya Hsuan , Zolitschka Bernd
Published: March 2020

Sediment facies provide vital information for the reconstruction of past environmental variability. Due to rising interest for paleoclimate data, sediment surveys are continually growing in importance as well as the amount of sediments to be discriminated into different facies. The conventional approach is to macroscopically determine sediment structure and colour and combine them with physical and chemical information - a time-consuming task heavily relying on the experience of the scientist in charge. Today, rapidly generated and high-resolution multiproxy sediment parameters are readily available from down-core scanning techniques and provide qualitative or even quantitative physical and chemical sediment properties. In 2016, an interdisciplinary research project WASA (Wadden Sea Archive) was launched to investigate palaeo-landscapes and environments of the Wadden Sea. The project has recovered 92 up to 5 m long sediment cores from the tidal flats, channels and off-shore around the island of Norderney (East Frisian Wadden Sea, Germany). Their facies were described by the conventional approach into glacioflucial sands, moraine, peat, tidal deposits, shoreface sediments, etc. In this study, those sediments were scanned by a micro X-ray fluorescence (µ-XRF) core scanner to obtain high-resolution records of multi-elemental data (2000 µm) and optical images (47 µm). Here we propose a supervised machine-learning application for the discrimination of sediment facies using these scanning data. Thus, the invested time and the potential bias common for the conventional approach can be reduced considerably. We expect that our approach will contribute to developing a more comprehensive and time-efficient automatic sediment facies discrimination.

Keywords: the Wadden Sea, µ-XRF core scanning, machine-learning, sediment facies discrimination
Left-lateral shearing before coeval exhumation between the high pressure Yuli belt and the underlying Mesozoic Tailuko belt? Insights from the Shoufeng fault in eastern Taiwan
Authors: Lee Jian-Cheng , Ho Gong-Ruei , Lee Yuan-Hsi , Yeh En-Chao , Byrne Tim , Chu Has-Tsu
Published: March 2020

Based on field investigations, microscopic observations, and available geophysical, geochemical and geochronological data, this study intends to better understand the structural characteristics of the Eurasian continental margin (e.g., the eastern Central Range in Taiwan) during subduction and exhumation while the Philippine Sea plate has been approaching in the vicinity of Taiwan since the Miocene time.  The eastern Central Range is composed of two major geological units: 1) the Tailuko belt, the Mesozoic metamorphic subduction complex, retro-metamorphosed in green schist facies and exhumed since late Miocene, and 2) the Yuli belt, continental margin rocks that contain high-pressure minerals (omphacite, glaucophane, garnet) with Miocene-Pliocene ages suggesting rapid exhumation from mantle depths of 40-50 km.

We conducted detailed field surveys around the Shoufeng fault which represents the boundary between the Tailuko belt and the Yuli belt. We found a mylonite zone of several kilometers wide in the boundary of these two belts. Based on the meso- and microscopic scale observations we define the boundary as ultra-mylonite, mylonite, and proto-mylonite zones. Within the ultra-mylonite and mylonite zones, rocks from two belts are intercalated each other in varied widths. The main dominant schistosity/cleavage in the mylonite zones (Sm/S3) remains the same orientation of striking in NE/NNE and dipping to the west. Also, the main composition layers, which we tentatively called S2 for the sake of field investigations, were more intensively deformed (i.e., crenulated, folded, etc.) from outside toward the core of the mylonite zones. As a result, the Sm/S3 becomes less persistent outside of the mylonite zones in the Yuli belt.

The mylonite zones exhibit left-lateral Sm/S3-related shearing without significant down-dip component. We also observed a general S2/S3-related top-to-west sense of shear across the two belts. As a consequence, we tend to interpret that the Yuli belt and the Tailuko belt have been mylonitically sheared (Sm/S3) in a left-lateral movement at the depth and that they exhumed coevally up to the surface level. The schistosity of the main composition layers S2 probably occurred before the mylonization during the transition from subduction to exhumation. The shallow dipping and less dominant S3 outside the mylonite zone might imply an upward unroofing process during the rapid exhumation of the eastern Central Range of Taiwan.
A basin-scale groundwater flow model in the Columbia Plateau (Pacific Northwest, USA); insights for management of fractured aquifer-types
Authors: Medici Giacomo
Published: March 2020

Mechanical discontinuities control groundwater flow in fractured aquifers. Bedding plane and sub-vertical discontinuities create fracture networks geometrically organized both horizontally and vertically in areas un-affected by compressional tectonic forces. In this structural setting, we use the Columbia River Basalt aquifer in the Palouse to show how the combination of previous acquired stable isotope data and geological, groundwater, and particle tracking modeling better describes groundwater flow in three dimensions. We present a steady-state flow model simulating backward particle traces from abstraction wells to the recharge boundaries. Backwards particle analysis coupled with the 14C isotope vertical concentration distribution shows how the aquifer system is characterized by two separate zones. A shallow (<120 mBGL) zone of freshwater circulation is characterized by higher 14C concentrations and low particle travel times with respect to the deeper (>120 mBGL) aquifer zone. Here, penetration of particles is partially impeded by the low vertical hydraulic conductivity of the volcano-sedimentary layers and recharge preferentially occurs in correspondence of discontinuities related to a geological unconformity. Hence, the outputs of a particle tracking analysis fits stable isotope data either validating a 3D groundwater flow model or aiding detail to conceptualization of a fractured aquifer.

The Columbia River Basalt aquifer is also horizontally anisotropic due to sub-vertical tectonic fractures which are related to gentle folding and faulting. This horizontal anisotropy significantly influences particle tracking analysis in the basin up to 120 mBGL. Well-head protection areas are defined globally by backward particle tracking analyses at shallow depths. Thus, as a consequence of this research we envisage introduction of horizontal anisotropies in groundwater flow models for definition of well capture zones.
Out of equilibrium sinuosity: The development of incised meandering channels in response to base-level fall
Authors: Dente Elad , Lensky Nadav , Morin Efrat , Enzel Yehouda
Published: March 2020

Meandering rivers and valleys are dominant landscape features on Earth and Mars, and central to a geomorphological debate: do sinuous channels actively develop during steepening of regional slope or whether they inherited the sinuosity of an ancient meandering channel through vertical incision? This and related questions were studied by field-scale case studies of channel evolution, numerical simulations, and physical laboratory experiments. Here, we document and investigate decadal- and field-scale formation of meandering valleys in perennial channels. These channels have incised into a homogeneous erodible substrate in response to the progressive Dead Sea level fall in recent decades (>30 m over 40 years). This unique study area enabled analysis of three clusters of adjacent elongating and incising channels with stable confined discharge, that evolved through an active increase in regional and channel slopes. The emerged slopes greatly vary along the study area and channels, allowing the test of slope impact under three primary settings: (a) relatively long and low gradients on shelf-like margins, (b) sharp basinward gradient increase on a shelf-slope transition, and (c) steepening slopes. These clusters triggered different channel and valley response by means of stream incision depth, channel sinuosity, and valley width. The sinuosity of the channels was actively increased only following steepening in the valley slope. During stable valley slope, the channels were mainly incising vertically, inheriting previous sinuous pattern. The highest sinuosity was developed in the channel within the most steepening slope, that was also developed the deepest and widest valley. Together with the Jordan River response to the same Dead Sea level fall in recent decades, these insights promote the interpretations regarding the evolution of incised meandering channels under changes in regional slope. Abundant evidence for chute cutoffs along an incised channel can imply that frequent overbank floods prevailed in the channel during the incision, whereas the absence of or rare evidence for such cutoffs can be the result of infrequent high-magnitude floods during the evolution.
Statistical properties of ions in bursty bulk flows
Authors: Wu Mingyu , Pan Zonghao , Chen Yangjun , Zhang Tielong
Published: March 2020

With the observations of THEMIS and MMS Mission, we have investigated the properties of ions in bursty bulk flows (BBFs). Based on analysis of 315 BBF events, we can obtain the statistical features of ions in the BBFs. The results can be summarized as follows: (1) the occurrence rate of BBFs is related with AE index, which is also confirmed by previous studies; (2) the ion number density in the duskside is nearly at the same level with that in the dawnside; (3) in the region -10RE > XGSM> -15RE(where REis the earth radius), the ion temperature in the duskside is much higher than that in the dawnside; (4) the ion temperature anisotropy T⊥/T∥ is weaker as BBFs close to the Earth; (5) corresponds to cold electrons (Te < 1.5 keV), the ratio of the ion and electron temperature Ti/Te can reach 10-15 and the temperature of ions and electrons have a linear correlation.
Statistical Properties of Field-Aligned Currents in the Plasma Sheet Boundary Layer
Authors: Chen Yuanqiang , Wu Mingyu , Wang Guoqiang , Pan Zonghao , Zhang Tielong
Published: March 2020

Field-aligned currents (FACs), also known as Birkeland currents, are the agents by which momentum and energy can be transferred to the ionosphere from solar wind and the magnetosphere, exhibiting a seasonal variation as that of ionospheric conductance at low altitude. By using magnetic field and plasma measurements from the Magntospheric Multiscale (MMS), we estimated the properties of the small-scale FACs in the plasma sheet boundary layer (PSBL) region. The occurrence rates of those FACs are larger near the midnight plane and near the flank region; they are also larger in the northern (summer) hemisphere than in the southern hemisphere, especially for the earthward FACs. Different distribution patterns as a function of plasma β are found for the Beam-type FACs and the Flow-type FACs (accompanied with observable perpendicular currents). The latter are closer to central plasma sheet (higher β) and their occurrence rate decreases linearly toward tail lobe (lower β), while the former mainly appear within the β range of 0.1 to 1. FAC magnitudes show little dependence on plasma β, while they would increase when approaching Earth generally. The occurrence rate and magnitude of FACs both increase from low to high geomagnetic activity, consistent with observation at ionospheric altitude. The main carriers for FACs in PSBL are thermal electrons, while cold electrons sometimes could also have contribution, especially under high geomagnetic activity. This study shows that FACs in the PSBL exhibit an asymmetry of occurrence rate between the northern and southern hemisphere and different signatures under low and high geomagnetic activity, which are consistent with FACs at ionospheric altitude. This demonstrates that FACs are significant in magnetosphere-ionosphere coupling and illustrates the possible ionospheric feedback effects to magnetosphere in the nightside.
Flexural toppling and the development of uphill-facing scarps along the Bedretto valley, Swiss Alps
Authors: Chigira Masahiro , Jaboyedoff Michel , Pedrazzini Andrea , Kojima Satoru
Published: March 2020

Uphill-facing scarps develop in the central Swiss Alps, particularly along the Upper Rhone valley, the Urseren valley, the Upper Rhine valley, and Bedretto valley. It has been argued whether they have gravitational origin, tectonic origin, or differential uplift after the deglaciation. We made geological survey and topographic interpretation in the Bedretto valley, in which the Ticino River flows from the west-southwest to east-northeast. The Bedretto valley slopes have shoulders on both sides of the valley at elevations of 1500 to 1900 m, below which is a lower U-shaped valley. Uphill-facing scarps develop more on the southern side slopes of the Bedretto valley, where is underlain mainly by mica schist of the Bedretto zone, than on the northern side slopes, where is underlain mainly by gneiss and slate. In addition, they develop much more on slopes higher than the slope shoulders, and the uphill-facing scarps on the lower U-shaped valley are much smaller in scale. Tributary valleys on the south side of the Bedretto valley go down into this lower U-shaped valley from the southeast with intervening ridges, and we surveyed along the valleys of Ri di Cristallina, Ri di Valleggio, and Val Cavagnolo. We found that steeply-dipping schistosity in the ridges is toppled valleyward with brittle fractures along the hinge zones, which are approximately along or slightly higher than the tributary valley bottom. Rock mass as thick as 300 m thus toppled. Flexural toppling of mica schist developed uphill-facing scarps, which were mostly along high-angle faults, some of which were recognized to have brittle crush zones. The flexural toppling generated extension field in the upper ridges, where rock mass apparently settled down along normal faults. The reason why the northern side slopes of the Bedretto valley have much smaller uphill facing scarps may be due to the rocks are mainly gneiss and also due to the numbers of faults are possibly much less than in the southern slopes . The facts that uphill facing scarps are mainly developed above the lower U-shaped valleys may be related to the longer time intervals of the exposure of slopes higher than the slope breaks to the atmosphere during the glacial age.
Highlighting the importance of topsoil in human life through a soil education program
Authors: Masuda Aiki , Yokoo Emi , Hirai Hideaki , Deguchi Akiko
Published: March 2020

This study aims to highlight the importance of topsoil in human life from the viewpoint of daily rice consumption in Japan. A questionnaire on rice and/or soil was distributed to elementary, junior high, and high school students and university students in order to investigate how much they know about soil and its importance. The results were reported using an earlier study (Hirai and Hirai, 2015). The findings revealed that most of the students recognized the soil function of plant production, but few recognized the area of paddy fields required to produce the amount of average rice consumed per person per year in Japan. In order to convey the importance of topsoil, an interactive class on “rice” was conducted with students in October 2019, as part of a soil education program. Before it, a rice hill with topsoil of 15 cm was taken from a paddy rice field and kept in a plastic container. We chose rice as the topic because Japanese students can easily relate to it. Students were told that to produce 150 g of edible rice, 70 g of dried rice is used. As part of an activity, they were asked to: 1) Count grains in 2 g of dried rice, and then calculate the number of grains in 70 g dried rice, 2) Observe a rice hill with topsoil , 3) Count the number of panicles of the rice plant and the number of rice hull in a panicle, 4) Multiply the number of rice hull with the panicle number to obtain the total number of rice hulls, and 5) Measure the total area and the weight of the topsoil. Thus, the students could understand how many rice hills with topsoil of 15 cm depth with a certain area are required to produce 150 g of edible rice. The students were also asked to touch and feel the soil and the rice plants, following a presentation about their learnings and findings. After this activity, a lecture from a professor of soil science was delivered. Moreover, the following questionnaire survey was conducted before and after the soil educational program aiming at recognizing the importance of soil. The number of participating students was 19, consisting of 5th and 6th graders of primary school and 1st to 3rd graders of junior high school. The following questions were asked: Q1. Would you like to have places with soil around where you live? Q2. If you prefer to have a place with soil around, what are the reasons behind it? Q3. Would you like to know more about soil? The number of students who answered Q2 with “because having a place with soil stops groundwater from drying up” increased from 5 to 15 after the program. In case of Q3, the number of students who answered “I would like to know as much as possible” increased from 10 to 18. Moreover, it is noteworthy that attendants stressed on touching the soil and measuring the area under rice plant cultivation.
Model forecast error correction based on the Local Dynamical Analog method: an example application to the ENSO forecast
Authors: Hou Zhaolu , Zuo Bin , Zhang Shaoqing , Huang Fei , Ding Ruiqiang , Duan Wansuo , Li Jianping
Published: March 2020

Numerical forecasts always have associated errors. Analogue correction methods combine numerical simulations with statistical analyses to reduce model forecast errors. However, identifying appropriate analogues remains a challenging task. Here, we use the Local Dynamical Analog (LDA) method to locate analogues and correct model forecast errors. As an example, an ENSO model forecast error correction experiment confirms that the LDA method locates more dynamical analogues of states of interest and better corrects forecast errors than do other methods. This is because the LDA method ensures similarity of the initial states and the evolution of both states. In addition, the LDA method can be applied using a scalar time series, which reduces the complexity of the dynamical system. Model forecast error correction using the LDA method provides a new approach to correcting state-dependent model errors and can be readily integrated with other advanced models.
Spatial-Temporal Distribution and Change of Seasonally Frozen Ground on the Tibetan Plateau from 1960 to 2014
Authors: Luo Siqiong
Published: March 2020

The change in spatial-temporal distribution of seasonally frozen ground (SFG) is an important indicator of climate change. Based on observed daily freeze depth of SFG from meteorological stations on the Tibetan Plateau (TP) from 1960 to 2014, the spatial-temporal characteristics and  trends in SFG were analyzed, and the relationships between them and climatic and geographical factors were explored. Spatial-temporal distribution of SFG on a regional scale was assessed by multiple regression functions. Results showed multi-year mean maximum freeze depth, freeze-thaw duration, freeze start date, and thaw end date demonstrate obvious distribution characteristics of climatic zones. A decreasing trend in maximum freeze depth and freeze-thaw duration occurred on the TP from 1960 to 2014. The freeze start date has been later and the thaw end date has been significantly earlier. Warming and wetting conditions of the soil resulted in a decrease in the maximum freeze depth and freeze-thaw duration, both spatially and temporally. The spatial distribution of SFG has been altered significantly by soil thermal conditions on the TP and could be assessed by elevation and latitude or by air temperature and precipitation, due to their high correlations. The regional average of maximum freeze depth and freeze-thaw duration caused by climatic and geographical factors was larger than those averaged using meteorological station data because most stations are located at lower altitudes. Maximum freeze depth and freeze-thaw duration has decreased sharply since 2000 on the entire TP.
Seismic rate change as a tool to investigate remote triggering of the 2010-2011 Canterbury earthquake sequence, New Zealand
Authors: Yin Yifan , Wiemer Stefan , Kissling Edi , Lanza Federica , Fry Bill
Published: March 2020

Crustal earthquakes in low deform rate regions are rare in the human life span but bear heavy losses when occurring. Limited observations also hinter robust earthquake forecasts. In this study, we use a high-resolution catalog to investigate the triggering of the 2010-2011 Canterbury earthquake sequence, New Zealand. The seismic sequence occurred in the North Canterbury Plains, a low-stress, low-seismicity region relatively close to active plate boundaries where large earthquakes are frequent, such as the 2009 MW 7.8 Dusky Sound Earthquake. To map the post-seismic stress transfers of remote large events acting in the region, we calculate the temporal and spatial seismic rate changes in the crust from 2005 to the 2010 Mw 7.1 Darfield Earthquake, the first mainshock of the Canterbury sequence. We use template matching analysis to obtain a new high-resolution seismic catalog that includes events previously undetected by routine network monitoring. Detection quality is further established through the usage of a Support Vector Machine classifier. Using the new catalog, we observe a seismic quiescence on the North Canterbury Plain between Dusky Sound Earthquake and the Darfield Earthquake. The quiescence is accompanied by a reduced rate in micro-seismicity, suggesting a lowered b-value in the region primed for the Canterbury sequence. The lack of proof of dynamic or static triggering suggests that complex fault interactions lead to the onset of the Darfield Earthquake.
Evaluation of Marine Boundary layer cloud in the NCEP Climate Forecast System (Version 2) via Stochastic Multicloud Model
Authors: Roy Kumar , Mukhopadhyay Parthasarathi , Krishna Ravuri Phani Murali , Goswami Bidyut Bikhash , Khouider Boualem
Published: March 2020

Marine boundary layer (MBL) cloud is one of the major sources of uncertainty in the climate models and they have been identified in the Intergovernmental Panel on Climate Change’s (IPCC’s) fourth assessment as a primary source of uncertainty in determining the sensitivity of climate models. Further simulating it realistically is a huge challenge. To better represent organized convection in the Climate Forecast System version 2 (CFSv2), a stochastic multicloud model (SMCM) parameterization is adopted and it has showed promising improvement in different features of tropical convection. But the simulation of marine boundary cloud in CFSv2 SMCM (EXP1) is yet to be ascertained. We have calibrated the model by using radar observations and followed Markov-chain process to generate key parameters like transition probability, required for EXP1. This paper describes climate simulations of the EXP1 and 25 year run is made and last 20years are analysed. It replaces pre-existing convection scheme (CTL) and shows improvement in many aspects of climate compared to CTL. In addition, global distribution of MBL cloud is also improved and it is also with better agreement with observational analysis, which is inaccurate in CTL. Further, the transition from stratocumulus to trade cumulus is well simulated in EXP1. These results are also supported also by quantitative analyses like Root Mean Square Error (RMSE) etc. The improvement seen in EXP1 can be largely attributed to the general improved in the representation of shallow and cumulus clouds compared to CTL.