bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of fire on sulfidic peat swamp sediments
Authors: Wong Vanessa , Williamson Tess , Etschmann Barbara , Wilson Sasha
Published: March 2020

Peat swamps contain substantial accumulations of organic matter due to waterlogging and slower decomposition rates. Peat swamps can be underlain by sulfidic sediments where there is  abundant iron and sulfate for reduction to form a range of sulfidic minerals, primarily pyrite (FeS2). Sulfidic sediments can acidify to produce sulfuric acid, similar to acid mine drainage (AMD) and acid sulfate soil (ASS) environments when oxidised, which can occur when water levels drop due to drainage or periods of drought. Discharging surface and shallow groundwater can therefore acidify adjacent lakes and waterways. These swamps can also present significant fire hazards when drying occurs. 

This study identified the chemical and mineralogical changes in sulfidic peat swamp sediments along a temperature gradient to simulate the effects of fire. We found that fire induced changes in the Fe-minerals to form a range iron (oxy)hydroxides and iron oxides such as magnetite, mghemite and haematite in increasing crystallinity  with increasing temperatures. pH initially decreased on drying a minimum of pH 3.15, before increasing with increasing temperature to 650oC to pH 4.86, which can mobilise environmentally important pH-sensitive metals. 

Peat swamps are highly susceptible to the effects of fire when surface- and shallow groundwater levels decrease as a result of extended drought or drainage. Fire can irreversibly alter underlying soil properties to induce changes in soil minerals and potentially impact the surrounding environment. 
Clustering analysis of soil gas chemical ratios as a potential geochemical tool for surface geothermal exploration
Authors: González-Moro Ángel M. , D'Auria Luca , Pérez Nemesio M.
Published: March 2020

Geochemistry is a fundamental tool in surface geothermal exploration. In particular, the analysis of the composition of the soil atmosphere, the measurement of diffuse CO2 flux and of the gas 222Rn activity are important parameters to detect and characterize the contribution of volcanic/hydrothermal sources in the diffuse soil degassing.

The analysis of the soil atmosphere usually consists of determining the chemical and isotopic composition of the gases, including concentrations and molar ratios of multiple chemical species (e.g. He, H2, N2, Ar, Ne, O2, CH4, CO2), as well as the C isotopic ratios (13C/12C). In practice a single geochemical survey provides tens of different parameters for each sampling point. Taking into account that a typical survey is composed of hundreds of sampling points, the huge amount of collected data requires effective data mining tools to perform analyses going beyond the simple mapping of concentrations and/or ratios and to detect hidden patterns in the dataset.

Among the most effective multivariate statistical tools is clustering analysis. This technique allows determining the presence of groups of points showing a given degree of similarity. In this work we used and compared two different clustering techniques: the K-means and the DBSCAN algorithms, applying them to a geochemical dataset related to surveys realized in 2010 in the southern part of the island of Tenerife (Canary Islands Spain) with the aim of geothermal exploration. We show how the clustering analysis allows determining the presence of areas characterized by a similar chemical and isotopic composition. The use of standard geochemical tools allows interpreting the nature of these areal groups in terms of their relevance for the purposes of surface geothermal exploration.
Aeolian transport on a wet beach: Field observations from the swash zone
Authors: Swann Christy , trimble sarah
Published: March 2020

Quantifying aeolian transport within the swash zone is critical to understanding feedbacks between aeolian and nearshore processes in coastal environments. In the swash zone, high moisture contents are thought to significantly limit the amount of sediment available for transport by wind. These assertions are supported by empirical relationships between the threshold for aeolian transport and moisture content that show gravimetric moisture contents greater than ~5% severely restrict the transport of windblown sand. Yet, during strong wind events aeolian transport can occur in the swash zone where moisture content is significantly higher. Here, we present field observations of fully-saturated aeolian transport on a wet beach and highlight the proficiency of winds to sustain aeolian transport in the swash zone.  

Field observations were collected during the passing of Tropical Storm Nester on a dissipative beach north of Corolla, North Carolina, USA in the early morning hours of October 19. 2019. Beach width ranged between ~50 and 100 meters and observations were made during a falling tide. Alignment of predominate winds and beach orientation provided a nearly unlimited fetch with an abundant sediment supply from the drier upper beach. Mean grain sizes of surface grab samples in the swash zone were 0.17 to 0.19 mm and moisture content in the swash zone ranged from 8 to 13% during the observational period.

Videos of fully developed, saturated transport in the form of nested streamers, approximately 5-20 cm wide, were recorded. A vertical array of cup and sonic anemometers measured near surface fluid flow. Cup anemometers were sampled at 1 Hz and observed wind velocities at 7, 18, 44, 68 and 93 cm above the surface. Ultrasonic anemometers sampled 3 dimensional velocity components at 32 Hz via at 53 and ~100 cm.  Sustained wind velocities were 9.5 m/s at 93 cm above the surface with gusts reaching 14 m/s. A series of vertically-segregating saltation traps captured particles in transport and showed minimal size-segregation with height. Gravimetric moisture content of captured saltation ranged from 0 to 4%.

Pulses of abundant aeolian transport during the storm were largely driven by largescale coherent eddies initiating transport from the drier upper beach. These upper beach sediments sustained transport on the lower, wet beach. The spatial and temporal variability of the exceedance of both fluid and impact thresholds strongly controls transport. These field observations demonstrate the proficiency of wind to transport of large volumes sand in the swash zone during strong alongshore wind events.
Quantification of terrestrial regional climate variability from a large database of pollen-based reconstructions and implications for future projections
Authors: Hébert Raphael , herzschuh Ulrike , Laepple Thomas
Published: March 2020

Multidecadal to millenial timescale climate variability has been investigated over the ocean

using extensive proxy data and it was found to yield coherent interproxy estimates of global and regional sea-surface temperature (SST) climate variability (Laepple and Huybers, 2014). Global Climate Model (GCM) simulations on the other hand, were found to exhibit an increasingly large deficit of regional SST climate variability for increasingly longer timescales.

Further investigation is needed to better quantify terrestrial climate variability for long

timescales and validate climate models.

Vegetation related proxies such as tree rings and pollen records are the most widespread

types of archives available to investigate terrestrial climate variability. Tree ring records are

particularly useful for short time scales estimates due to their annual resolution, while pollen-based reconstructions are necessary to cover the longer timescales. In the present work, we use a large database of 1873 pollen records covering the northern hemisphere in order to quantify Holocene vegetation and climate variability for the first time at centennial to multi-millenial timescales.

To ensure the robustness of our results, we are particularly interested in the spatio-temporal representativity of the archived signal in pollen records after taking into account the effective spatial scale, the intermittent and irregular sampling, the age-uncertainty and the sediment mixing effect. A careful treatment of the proxy formation allows us to investigate the spatial correlation structure of the pollen-based climate reconstructions as a function of timescales. The pollen data results are then contrasted with the analysis replicated using transient Holocene simulations produced with state-of-the-art climate models as well as stochastic climate model simulations.Our results indicate a substantial gap in terrestrial climate variability between the climate model simulations and the pollen reconstructions at centennial to multi-millenial timescales, mirroring the variability gap found in the marine domain. Finally, we investigate how future climate model projections with greater internal variability would be affected, and how this increases the uncertainty of regional land temperature projections.
Isotopic fingerprinting of fugitive methane and CO2 from the Western Canada Sedimentary Basin (WCSB): Data documentation and impact
Authors: Muehlenbachs Kalis , Gonzalez Arismendi Gabriela
Published: March 2020

The general public, industry and regulators seek information about both intentional and unintentional greenhouse gas (GHG)  emissions from energy wells. Minimizing these emissions may be one of the easiest steps to reaching reduction targets. ẟ13C is a common tool used to assess sources of atmospheric methane. Here we report and map the isotopic composition of 1280 production gases from energy wells in the Western Canada Sedimentary Basin (WCSB), which mark the ẟ13C of downstream GHG emissions in the production and transmission network. The WCSB is a worldwide recognized hydrocarbon producer, with more than 450,000 energy wells drilled only in Alberta. Produced methane ẟ13C ranges from -70‰ (VPDB – biogenic source) to -23‰ (VPDB – over mature shale) averaging, -47.2‰. Many of the currently producing, shut-in and abandoned wells also emit fugitive gas through surface casings (SCVF) and soil/ground migration (GM).  Their ẟ13C of the fugitive gases usually indicates a shallower source than the production target (average SCVF ẟ13Cmethane= - 55.6 ‰, GM ẟ13Cmethane= - 58.0 ‰, and average SCVF ẟ13CO2= - 55.6 ‰, GM ẟ13 ẟ13CO2= -15.8 ‰). Mapping (isoscapes) of isotope values from 2800 SCVF, and 1800 GM gases sampled across WCSB, show that geology and topography constrain the source of leaks. The spatial distribution and wide range of ẟ13C of fugitive methane across the WCSB provide insights and data to climate modellers seeking to attribute atmospheric methane sources but is also relevant for mitigation of emissions as well as informing regulators.
Verification of Probabilistic Precipitation Forecasts in Metropolitan Area of Valley of Mexico Using the ECMWF Ensemble Prediction System
Authors: López López Marco Rodrigo , Pedrozo-Acuña Adrian
Published: March 2020

Security against extreme rainfall events is a basic need for social and economic development. The climate projections suggest a changing world in the rainfall patterns, forecasting increasingly extreme rainfall and droughts events; nevertheless, there is a lot of uncertainty in the future hydrologic cycle of the basins, where rainfall is the more complicated weather phenomena to predict. To deal with this difficulty, process such as assimilation, a better description of weather phenomena and the use of ensembles have been developed. Such technologic advances have resulted in the use of Numerical Weather Prediction Models (NWP) and its chain with Ensemble Prediction Systems (EPS), which have been recognized as valuable tools for a good Warning System.

Currently, Mexico City is one of the largest metropolis of the world with more than 22 million of inhabitants and serious difficulties oh hydraulic infrastructure. The city depends completely on the sewage system to prevent and mitigate floods. For these reasons, this work proposes to evaluate the deterministic and meteorological ensemble precipitation forecasts issued by the European Centre for Medium Range Weather Forecasting (ECMWF) for two study cases: 1) Mexico Valley Basin and 2) Mexico City. For study case 1, the precipitation forecasts were compared against 24 hours accumulated observed rainfall, issued by CLICOM System (clicom-mex.cicese.mx) and for 2007 to 2014 period time. For study case 2, the forecast were compared against observed real-time precipitation data issued by the Hydrological Observatory of Engineering Institute (OHIIUNAM), using a lead-time and time step of 90 hours and 6 hours respectively; and carried out for the rainy season of years 2017 and 2018. For this, deterministic and probabilistic verification metrics were applied (Relative Operating Characteristic, Reliability Diagram and the Brier Score) in order to measure the quality and performance of the forecasts products and its potential use for floods prediction in Mexico City.

The evaluation of the results shows that the observed events are within the range of the probability distribution, which means that the EPS constitutes a good representation of the possible atmospheric scenarios along the time horizon. Metrics establish a greater reliability for forecast in the range of 2 to 10 mm of accumulated rainfall in 24 hours; in the other hand, there is a good discrimination and accuracy of observed and unobserved events of accumulated precipitation of 1 mm in 6 hours.
Diffuse CO2 degassing monitoring of the Tenerife North–South Rift Zone (NSRZ) volcano, Canary Islands
Authors: Cordero-Vaca María , Figueiredo Carolina A. , Czwakiel Nicole L. , Padrón Eleazar , Melián Gladys V. , Alonso Mar , Asensio-Ramos María , Hernández-Ramos William , Hernández Pedro A. , Pérez Nemesio M.
Published: March 2020

Tenerife (2,034 km2) is the largest of the Canary Islands and the North South Rift Zone (NSRZ) is one of the three active volcanic rift-zones of the island. The NSRZ (325 km2) is characterized mainly by effusive activity of basaltic lavas forming spatter and cinder cones and comprises 139 monogenetic cones representing the most common eruptive activity occurred on the island during the last 1Ma. In order to provide a multidisciplinary approach to monitor potential volcanic activity changes at the NSRZ volcano, diffuse CO2 emission surveys have been undertaken since 2002. This study shows the results of the last soil CO2 efflux survey undertaken in summer 2019, with ⁓600 soil gas sampling sites homogenously distributed in the study area. Soil CO2 efflux measurements were performed at the surface environment by means of a portable non-dispersive infrared spectrophotometer (NDIR) LICOR Li820 following the accumulation chamber method. Soil CO2 efflux values ranged from non-detectable (⁓0.5 g m-2 d-1) up to 30 g m-2 d-1, with an average value of 2.6 g m-2 d-1. In order to distinguish the existence of different geochemical populations on the soil CO2 efflux data, a Sinclair graphical analysis was done. The average value of background population was 2.1 g m-2 d-1 and that of peak population was 18.5 g m-2 d-1, representing the 97% and the 1% of the total data, respectively. To quantify the total CO2 emission rate from the NSRZ volcano a sequential Gaussian simulation (sGs) was used as interpolation method. The diffuse CO2 emission rate for the studied area was estimated in 2019 in 819 ± 18 t d-1, ranging from 466 to 819 t d-1 between 2002 and 2019, with the highest value measured in 2015 (707 t d-1). The temporal evolution of diffuse CO2 emission at the NSRZ shows a clear relationship with the volcano seismic activity in and around Tenerife Island, which started to taking place from the end of 2016. This study demonstrates the importance of studies of soil CO2 efflux at the NSRZ volcano of Tenerife island as an effective volcanic monitoring tool, especially in areas where there is no visible degassing (fumaroles, etc.)
Soil carbon and soil moisture dynamic redistribution in a banded ecosystem
Authors: Quijano Baron Juan Pablo , Saco Patricia , Jaskierniak Dominik , Rodriguez Jose
Published: March 2020

Arid and semiarid environments accounts approximately 30% of the Earth’s continental surface and are especially sensitive to degradation or loss of their ecosystem functionality. In these ecosystems, vegetation patterns (e.g. banded vegetation) can be found as the adaptive response of the system to resource redistribution (runoff and sediments) and limitation (soil moisture and nutrients). The patterns consist on alternating densely vegetated bands (or ‘groves’) and bare areas (or ‘intergroves’), and can be found in large regions of Africa, Asia, Australia and North America. Understanding the mechanism that regulate banded vegetation ecosystems is critical in order to identify the dynamic behaviour and maintain their functionality. In this work, we model the spatial distribution of soil moisture and soil organic carbon, in order to analyse how differences on the availability of resources can explain the functionality of the banded vegetation systems. We are studying a catchment in Bond Springs, 25 km north of Alice Springs, characterized by the presence of Acacia Aneura trees (Mulga) aligned in bands along the terrain. We use a new model: COPLAS, a tool that couples a Landform Evolution Model with dynamic vegetation and carbon pools modules. It tracks the carbon from the photosynthesis until it becomes soil carbon and the mobilization/redistribution due soil erosion. Results of the model were compared with fieldwork conducted in fifty-three soil samples and terrain surveying with unmanned aerial vehicle. Our results indicate good agreement between the model and the measurements. We found that soil moisture uphill the bands is around 33% more than downhill, and close to 120% more than in bare soil. This result could be explained because a portion of the runoff, generated from bare intercanopy patches, is redistributed downslope and infiltrated uphill the vegetated areas. Moreover, soil carbon is 20% more downhill than uphill the bands because of deposited alluvium and litter downhill and possible less microbial respiration and decomposition due smaller soil moisture content. Additionally, we found a tendency of higher soil carbon concentrations going downhill the catchment. Overall, these findings show the heterogeneous distribution of resources in the area that could explain the ecosystem functionality and highlight the importance of modelling and measuring arid and semiarid ecosystems in order to understand their dynamic behaviour.
Hyperbolic geometry of earthquake networks
Authors: Zaliapin Ilya , Henricksen Karla , Zuev Konstantin
Published: March 2020

We examine the space-time-magnitude distribution of earthquakes using the Gromov hyperbolic property of metric spaces. The Gromov δ-hyperbolicity quantifies the curvature of a metric space via so-called four-point condition, which is a computationally convenient analog of the famous thin triangle property. We estimate the standard and scaled values of the δ-parameter for the observed earthquakes of Southern California during 1981 – 2017 according to the catalog of Hauksson et al. [2012], the global seismicity according to the NCEDC catalog during 2000 – 2015, and synthetic seismicity produced by the ETAS model with parameters fit for Southern California. In this analysis, a set of earthquakes is represented by a point field in space-time-energy domain D. The Baiesi-Paczuski asymmetric proximity η, which has been shown efficient in applied cluster analysis of natural and human-induced seismicity and acoustic emission experiments, is used to quantify the distances between the earthquakes. The analyses performed in the earthquake space (D,η) and in the corresponding proximity networks show that earthquake field is strongly hyperbolic, i.e. it is characterized by small values of δ. We show that the Baiesi-Paczuski proximity is a natural approximation to a proper hyperbolic metric in the space-time-magnitude domain of earthquakes, with the b-value related to the space curvature. We discuss the hyperbolic properties in terms of the examined earthquake field. The results provide a novel insight into the geometry and dynamics of seismicity and expand the list of natural processes characterized by underlying hyperbolicity.
Induced or triggered? The deadly February 2019 Rongxian-Weiyuan ML 4.9 earthquake in the shale gas field in Sichuan, China
Authors: Yang Hongfeng , Zhou Pengcheng , Fang Nan , Zhu Gaohua , Xu Wenbin , Su Jinrong , Meng Fanbao , Chu Risheng
Published: March 2020

Coinciding with the extensive hydraulic fracturing activities in the southern Sichuan basin, seismicity in the region has surged in the past a few years, including a number of earthquakes with magnitudes larger than 5. On 25 February 2019, an ML4.9 earthquake struck the Rongxian County, Sichuan, China and caused 2 fatalities and 12 injuries, the first deadly earthquake associated with shale gas production. The earthquake was preceded by two foreshocks with magnitudes of ML4.7 and ML4.3 within two days. We relocated the earthquake sequence using local and regional seismic network, and obtained the focal depths of the mainshock and two foreshocks at 1 and 3 km, respectively, much shallower than the report from catalogue. Most other smaller quakes were located at 2-6 km. The mainshock had also been well captured by InSAR images, which confirmed the shallow depth of ~1 km. Both seismic and geodetic data yielded thrust faulting mechanism for the mainshock, consistent with the mapped Molin fault in the region. The two foreshocks, however, occurred on an unmapped fault that has different orientation than the Molin fault. Injection wells are found in the vicinity of the two foreshocks and the fracking depth (~2.7 km) coincides with their focal depths, suggesting a possible causal relationship. The mainshock is located in the region with positive Coulomb failure stress caused the two foreshocks. The value of Coulomb failure stress change is 0.03 bar, smaller than the typical static triggering threshold. Therefore, the mainshock is likely caused by fracking by poroelastic stress transfer.
Development, Characterization and Testing of a Drone-based Sampling Method for Investigations of Ice-Nucleating Particles
Authors: Bieber Paul , Seifried Teresa M. , Gratzl Jürgen , Burkart Julia , Kasper-Giebl Anne , Schmale III David G. , Grothe Hinrich
Published: March 2020

Terrestrial ecosystems can contribute various particles to the troposphere, some of which are known for their ice nucleation activity. Most of the land-surface in Europe is covered with forests and fields, representing potential sources of ice nucleation active bioaerosols in form of pollen grains, fungal spores and bacterial cells. The presence of biogenic ice-nucleating particles (INPs) in clouds leads to heterogeneous freezing events and therefore influences the hydrological cycle and the Earth’s climate. Many studies focus on measurements and characterizations of INPs in clouds using aircrafts or sample on ground with stationary devices. Less is known about the actual emission and transport to high tropospheric layers. We focused on the development of an efficient sampling device that can be attached to small scale drones, such as the DJI Phantom 4 model. The Drone-based Aerosol Particles Sampling Impinger/Impactor (DAPSI) system was developed to sample airborne INPs above emission sources. It includes a cascade impactor that collects particles with size resolution and a self-build impinging system that accumulates INPs in a sterile solution. Additionally, the system contains an electric sensor for environmental data records (temperature, relative humidity and air pressure) as well as an optical particle counter to monitor particular matter concentrations during flight times. This study leads through the building, characterization and test-campaign of DAPSI. We present a validation test, regarding the sampling effectivity to sample aerosols (polystyrene latex spheres and INPs) as well as results from the first field campaign which took place in a rural sampling site in the Austrian Alps. Fluorescence- and cryo-microscopic assays show auto-fluorescent particles and heterogeneous ice nucleation activity of DAPSI samples. We highlight the opportunity to use DAPSI with small un(wo)manned aerial vehicles during field campaigns to sample and identify biogenic INPs in vertical and spatial resolution above emission sources.
Influence of He++ and shock geometry on interplanetary shocks in the solar wind: 2D Hybrid simulations
Authors: Preisser Luis , Blanco-Cano Xochitl , Trotta Domenico , Burgess David , Kajdic Primoz
Published: March 2020

Alpha particles (He++) are the most important minor ion species in the solar wind, constituting typically about 5% of the total ion number density. When crossing an interplanetary shock protons and He++ particles are accelerated differently due to their different charge-to-mass ratio. This behavior can produce changes in the velocity distribution function (VDF) for both species in the immediate downstream region generating anisotropy in the temperature which is considered to be the energy source for various phenomena such as ion cyclotron and mirror mode waves for example. How these changes in temperature anisotropy and shock structure depend on the percentage of He++ particles and the geometry of the shock is not completely understood. In this work we perform various 2D local hybrid simulations (particle ions, massless fluid electrons) with similar characteristics (e.g., Mach number) to observed interplanetary shocks for both quasi-parallel and quasi-perpendicular geometries including self-consistently different percentages of He++ particles. We find that the change of the initial θBn leads to variations of the efficiency with which particles can escape to the upstream region facilitating or not the formation of compressive structures in the magnetic field that will produce increments in perpendicular temperature. The regions where both temperature anisotropy and compressive fluctuations appear tend to be more extended and reach higher values as the He++ content in the simulations increase.
Characteristics of Soil nutrient loss under different rainfall pattern in slope plots
Authors: Wang Tian , Huang Zhilin , Ma Liang , Zeng Lixiong
Published: March 2020

Rainfall intensity and duration directly affect the process of soil nutrient loss. In this paper, long-term, low-intensity rainfall (LL) (58.4mm rainfall, 605min duration) and short-term, high-intensity rainfall (SH) (59.2mm rainfall, 287min duration) were selected to study the pathway for soil nitrogen and phosphorus loss and load differentiation under different rainfall modes by using a slope experiment plot. The results indicated that: (1) The difference between the runoff duration of LL (3410min) and that of SH (410min) was obvious, and the runoff rate was 14.44% and 28.55%, respectively; (2) There were different nutrient concentration distributions. On one hand, the concentration of TN in the surface flow was lower than that in the interflow. The average TN concentration in the surface flow of LL and SH was 13.7 and 16.94 mg·L-1, respectively. The average TN concentration in the interflow of LL and SH was 59.25 and 50.89 mg·L-1, respectively. On the other hand, the concentration of TP in the surface flow was higher than that in the interflow. The concentration of TP ranged from 0.42 to 1.44 mg·L-1 in the surface flow, and from 0.21 to 0.91 mg·L-1 in the interflow; (3) The interflow is the main pathway of nitrogen loss, while the surface flow is the main pathway of phosphorus loss. The respective TN load of LL and SH runoff was 4.04 and 8.49 kg·hm-2, of which the contribution rate of the interflow was 88.49% and 85.54%, respectively. Additionally, the respective TP load of LL and SH runoff was 0.11 and 0.33 kg·hm-2, of which the contribution rate of the surface flow was 65.79% and 70.67%, respectively; (4) The amount of rainfall was almost the same but its intensity was different. High intensity rainfall would cause greater soil nutrient loss. The amount of total nitrogen and phosphorus loss in a sloppy land due to SH rainfall was 2-3 times higher than that due to LL rainfall.
Investigating land use and land cover changes in Dublin, Ireland using Satellite Imagery: A comparative analysis
Authors: Basu Bidroha , Sarkar Basu Arunima , Sannigrahi Srikanta , Pilla Francesco
Published: March 2020

Over the past few decades, there has been over increasing pressure on land due to population growth, urbanization, agriculture expansion and industrialization. The change in land use and land cover (LULC) pattern are highly dependent on human intervention. Deforestation pattern has started due to growth of suburbs, cities, and industrial land. The alarming rate in change of LULC pattern was on a rising trend since 1990s and has been increasing over time. This study focuses on analyzing the changes in LULC pattern in Dublin, Ireland over the past two decades using remotely sensed LANDSAT satellite imagery data, and quantify the effect of LULC change in streamflow simulation in watershed at Dublin by using rainfall-runoff model. Benefit of using remotely sensed image to investigate LULC changes include availability of high-resolution spatial data at free of cost, images captured at high temporal resolution to monitor the changes in LULC during both seasonal and yearly timescale and readily availability of data. The potential classification of landforms has been done by performing both supervised as well as unsupervised classification. The results obtained from the classified images have been compared to google earth images to understand the accuracy of the image classification. The change in LULC can be characterized by changes in building density and urban/artificial area (build up areas increase due to population growth), changes in vegetation area as well as vegetation health, changes in waterbodies and barren land. Furthermore, a set of indices such as vegetation index, building index, water index and drought index were estimated, and their changes were monitored over time. Results of this analysis can be used to understand the driving factors affecting the changes in LULC and to develop mathematical models to predict future changes in landforms. Soil Water Assessment Tool (SWAT) based rainfall-runoff model were used to simulate the changes in runoff due to the LULC changes in watershed over two decades. The developed framework is highly replicable because of the used LANDSAT data and can be applied to generate essential information for conservation and management of green/forest lands, as well as changes in water availability and water stress in the assessed area.
Cropland carbon uptake delayed by 2019 U.S. Midwest floods
Authors: Yin Yi , Byrne Branden , Liu Junjie , Wennberg Paul , Köhler Philipp , Humphrey Vincent , Magney Troy , Davis Kenneth , Gerken Tobias , Feng Sha , Digangi Joshua , Frankenberg Christian
Published: March 2020

While large-scale floods directly impact human lives and infrastructures, they also profoundly impact agricultural productivity. New satellite observations of vegetation activity and atmospheric CO2 offer the opportunity to quantify the effects of such extreme events on cropland carbon sequestration, which are important for mitigation strategies. Widespread flooding during spring and early summer 2019 delayed crop planting across the U.S. Midwest. As a result, satellite observations of solar-induced chlorophyll fluorescence (SIF) from TROPOspheric Monitoring Instrument (TROPOMI) and Orbiting Carbon Observatory (OCO-2) reveal a shift of 16 days in the seasonal cycle of photosynthetic activity relative to 2018, along with a 15% lower peak photosynthesis. We estimate the 2019 anomaly to have led to a reduction of -0.21 PgC in gross primary production (GPP) in June and July, partially compensated in August and September (+0.14 PgC). The extension of the 2019 growing season into late September is likely to have benefited from increased water availability and late-season temperature. Ultimately, this change is predicted to reduce the crop yield over most of the midwest Corn/Soy belt by ~15%. Using an atmospheric transport model, we show that a decline of ~0.1 PgC in the net carbon uptake during June and July is consistent with observed CO2 enhancements from Atmospheric Carbon and Transport - America (ACT-America) aircraft and OCO-2. This study quantifies the impact of floods on cropland productivity and demonstrates the potential of combining SIF with atmospheric CO2 observations to monitor regional carbon flux anomalies.
Different controlling factors of pore features between marine shale and transitional shale in the Upper Yangtze region, South China
Authors: Jiang Hongyang , Jiang Zhenxue , Li Xin
Published: March 2020

Compared with marine shale with plentiful research and successful exploration, fewer studies on transitional shale reservoirs limit further exploitation of shale gas. In this paper, comparative analysis, between Lower Silurian marine shale and Upper Permian transitional shale in the Upper Yangtze region, is carried out to analysis pore features of both shales and the main controlling factors, which can provide theoretical guidance for further exploration. A combination of methods is ultilized in terms of organic-chemistry geology measurement, X-ray diffraction (XRD), high-pressure mercury injection, gas adsorption, and focused ion beam milling and scanning electron microscopy (FIB-SEM). The results show that Lower Silurian marine shale and Upper Permian transitional shale have similar organic matter (OM) abundance (2.72% and 2.31%) and thermal degree (2.56wt%Ro and 2.68wt%Ro). However, the kerogen of Lower Silurian shale is type I derived from algae and plankton, while that of Upper Permian shale is mainly type III from higher plant debris. As for mineral composition, Siliceous minerals (> 43wt%) account for the majority in Lower Silurian shale, while clay (> 57wt%) is the main mineral in Upper Permian shale. Variations in material basis trigger to differences in pore characteristics between the two shales. Firstly, the pores in Lower Silurian shale are mostly hosted by OM with an average pore diameter of 7.94 nm, while Upper Permian shale mainly develops pores associated with clay minerals with an average pore diameter of 28.60nm. Moreover, Lower Silurian shale presented relatively higher pore properties than Upper Permian in both average pore volume (0.020ml/g and 0.015ml/g) and average pore surface area (7.99 m2/g and 1.2 m2/g). Various factors lead to the differences in pore types and pore properties between the two shales. For marine shale, OM with thermal convertibility tend to be mobilizable and porous. OM-hosted pores are the dominated type which is controlled by OM abandauce and thermal degree. However, in transitional shale, OM is featured by phase stability without porous feature. Pores associated with clay flakes are the main type which is controlled by the specifc material composition. Hence, the discrepancies of pore properties may be attributed to material diversities between marine shale and transitional shale.
Watershed water-energy balance dynamics and their association with diverse influencing factors at multiple time scales
Authors: Huang Shengzhi , Zhao Jing , Ren Kang
Published: March 2020

The Budyko curve is an effective tool for estimating how precipitation (P) partition into evapotranspiration (E) and streamflow (Q). Controlling the shape of the Budyko curve, the Budyko parameter represents the superimposed impact of various periodic factors (including climatic factors, catchment characteristics, teleconnection factors and anthropogenic activities) on the watershed water-energy balance dynamics, and such superimposed impact is not conducive to identifying the driving factors of the dynamic change of Budyko parameter at different time scales, and thus affect the parameter estimation. Here we obtain the dynamic change of Budyko parameter for the Wei River Basin (WRB)-a typical Loess Plateau region in China based on a 11-years moving window, and then adopt the Empirical Mode Decomposition (EMD) method to reveal the relationships between influencing factors and Budyko parameter series at multiple time scales by considering the interplay among different influencing factors. Results indicate that (1) Budyko parameter series are decomposed into 4-, 12-, 20-, exceeding 20-year time scale oscillations and a residual component with an significantly increasing trend in the upstream of the WRB (UWR) and the middle and lower reaches of the WRB (MDWR), a non-significantly decreasing trend in the Jing River Basin (JRB) and Beiluo River Basin (BLRB); (2) by analyzing the residual trend component, evaporation ratio (E/P), soil moisture (SM) and effective irrigated area (EIA) are found to induce the significant increase of parameter in the UWR, whereas that in the MDWR is dominated by baseflow (BF) and Niño 3.4; (3) parameter dynamics at the 4-year time scale is dominated by E/P, aridity index (EP/P), BF and SM; BF, PDO and sunspots attribute to the dynamics at 12-year time scale; all the factors except BF and SM contribute to the dynamics at 20- or exceeding 20-year time scales. The results of this study will help identify the connection between watershed water-energy balance dynamics and changing environment at multiple time scales, and also be beneficial for guiding water resources management and ecological development planning on the Loess Plateau region.
Effect of SST gradient caused by Typhoon-Generated Cold Wake on the Subsequent Typhoon Tembin in models of varying resolutions
Authors: Moon Mincheol , Ha Kyung-Ja
Published: March 2020

The Weather Research and Forecast (WRF) models have been used to investigate the sensitivity of simulations of Typhoon Tembin (1214) to changes in three horizontal grid spacings of 12km, 8km, and 6km and the effect of the cold wake generated by the previous Typhoon Bolaven (1215). It was observed that Bolaven-generated cold wakes cooled up to 7 °C in the sea around the Korean Peninsula. There are many previous studies on track dynamics influenced by sea surface temperature (SST) gradient due to the cold wakes. However, the intensity and precipitation of the following tropical cyclone (TC) is not yet certain. Here we show that the effect of SST gradient on the following TC are examined with WRF models of varying resolutions using modified SST from observed real-time data of the Ieodo Ocean Research Station and the Yellow Sea buoy in Korea. In the track of TC, a higher resolution showed the faster and more eastward movement of TCs in all SST conditions. TC tends to move more eastward at all resolutions particularly when the cold wake is generated in the western region of TC. When there is no cold wake, the intensity of TC is very sensitive to the resolution of the experiment. If a cold wake is maintained on the western (eastern) sides, the intensity of TC is weaker(stronger) than no cold wake experiment and is less sensitive to differences in resolution. The precipitation rate of TCs in the cold wake of the eastern (western) region is lower (higher) than when there is no wake. As the aspect of horizontal resolutions, the precipitation rate of TC in higher resolution shows stronger than lower resolution. The TC-generated cold wake significantly affects intensity and movement in cold wake cases in the western region, regardless of the horizontal grid, for various reasons.
Regional source apportionment of ozone and PM2.5 during the EXPLORE-YRD campaign in the Yangtze River Delta region of China
Authors: Hu Jianlin , Li Lin , Li Jingyi , Wang Xueying , Gong Kangjia
Published: March 2020

Although the air quality in China has been improved by collaborative efforts dedicating to mitigate the haze pollution, PM2.5 concentrations still remain high levels and the issue of increasing O3 concentration has attracted more attention of the public. The YRD region has been suffering from both the PM2.5 and O3 pollution problems. To investigate the formation mechanisms and sources of PM2.5 and O3 in this region, a comprehensive EXPLORE-YRD campaign (EXPeriment on the eLucidation of theatmospheric Oxidation capacity and aerosol foRmation, and their Effects inYangtze River Delta) was carried out in May - June 2018. In this study, we investigate the contributions of different source categories to PM2.5 and O3. A source-oriented 3-D air quality model (CMAQ) was applied to analyze contributions of different emission sources to PM2.5 and O3 in the YRD region. Emissions were divided into eight source categories: industry, power, transportation, residential, agriculture, biogenic, wildfire, and other countries. Contribution from individual source category was quantified. The importance of anthropogenic and natural sources to PM2.5 and O3 was discussed.
Generation of response spectrum compatible earthquake seismogram considering phase characteristics of possible earthquake motions of site
Authors: Park Hyung-Choon , Oh Hyun-Ju
Published: March 2020

For seismic analysis of complex and non-linear structure system, a seismic code recommends a dynamic time history analysis. In these cases, the input earthquake seismograms should be needed, and these input earthquake seismograms must be compatible with design response spectrum and reflect the site seismic characteristics including information about a fault and wave travel path between the fault and the site. The foreshocks, main shock and aftershocks of earthquake measured in the target area can be assumed to be the output signals of the system consisting of the fault and the wave travel path between the fault and the site. Each earthquake seismogram is considered as a amplitude modulated (AM) signal defined by the magnitude (or energy) and phase function with time. The probability distribution function (PDF) of the magnitude and phase function can be evaluated through the statistical and harmonic wavelet analysis of the measured output signals and these magnitude and phase PDFs include sufficient information to generate the possible output earthquake seismograms of the fault and travel path system for a site, which mean the phase and magnitude PDFs represent a site seismic characteristics.

In this paper, the method to generate the possible design response spectrum compatible earthquake seismograms based on the measured foreshocks, main shock and aftershocks of earthquake is proposed. At first the proposed method generate possible earthquake signals reflecting the phase characteristic of a site, and then modify the magnitude of these earthquake seismograms to determine the response spectrum compatible earthquake motions.  
Seabed mapping of tropical tidal channels, NE Brazil
Authors: Lima Ferreira Andressa , Vital Helenice , Gomes Moab , Aquino da Silva Andre , Perez Yoe
Published: March 2020

The Galinhos-tidal-channel system is located in the Brazilian equatorial margin, northeastern coast of Rio Grande do Norte State. The economic importance of the region began around 1600s and continues until today with salt exports, later shrimp farms, handmade fishing, oil and gas industry, ecotourism and wind energy. A spit, behind which an intricate system of tidal channels has developed, with practically absent riverine influence, characterizes the area. The integration of interferometric sonographic data (total of 4.7 km2), calibrated with sediment samples, and radar images were used to map geomorphological features on the area.  The ALOS PALSAR image, allowed to integrate the altitude information of the emerged and submerged portions, resulting in efficient method for coastal flooding areas and substrate mapping. The sonographic study allowed recognizing bedforms, which are important morphological elements that influence water and sediment discharge. Four main types of submerged geomorphic units were identified: a) 2D sandy dunes, b) 3D sandy dunes c) muddy flatbeds and d) irregular beds. Dunes were classified according to their size into small, medium and large. Bathymetric data revealed that depths from 2 to 8 m along the area. The main tidal channel Galinhos has a width of 900m, 12km long, irregular bottom, and asymmetrical margins. The Pisa Sal tidal channel has an average width of 150m and 3km long, U shaped cross-section, slight asymmetric margins and slightly irregular bottom. Deepest parts occurs close to its mouth (between 6,5m and 8m), gradually decreasing until they reach 5m on its inner portion. The Tomaz tidal channel, until to central portion has an asymmetrical bed with the highest depths on its right side reaching 7m. Its left side range from 5.5m to 6m. In the south portion, this channel becomes shallower (5m) and its asymmetry is reversed. After splitting the channel width is reduced from 260m to 140m and the bottom becomes less irregular and flat sometimes. In this portion, the highest depths reach 7m. The data made it possible to identify the regions of higher and lower altitudes using as reference the mean sea level. Altitudes throughout the region range from 0 (sea level) to 20m and come from local topographic elevation. The south portion concentrates altitudes above 10m and the lower regions are located in the central portion of the area. The central portion is the flattest and this behaviour extends over 5km to the dunes located in the Galinhos spit, when the altitudes exceed values above 10m. The Galinhos spit integrates an area with average altitude ranging from two to seven m. Flooded or wet regions were well delimited due to non-penetration or absorption of electromagnetic energy (low frequency) when it interacts with the water dynamics; however, results are better where the depth is higher than 3m.
Assess the impacts of different land cover datasets on land surface hydrological process in Community Earth System Model (CESM)
Authors: Ni Shaoqiang , Lu Hui
Published: March 2020

By changing matter and energy exchange, biogeochemical process and geophysical process, land use and land cover changes have crucial effects on the earth system modelling. Previous studies have focused on reconstructing the land use and land cover change to be a continuous changing process over time considering human and natural factors. The real land cover change processes have rarely been taken into consideration in the simulation of earth system. Using Gong global land cover mapping products (1985-2015) and the Lawrence land cover dataset (default) in CESM, this study have quantitatively compared the differences in plant function types (PFT) between two products. The results show the land cover changes in default dataset are slowly changing processes with little variation from year to year. In contrast, the Gong global mapping products express a noticeable drastic change tendency between adjacent years. Driving the model with different land cover datasets, our results indicates that globally land evapotranspiration (ET) is dramatically impacted by the land cover changes, especially in areas with distinct tree changes. Also the land cover change can cause a certain proportion variation in soil water (-50%-65%) and runoff (-60%-60%, even >90% in some special grid points) in a global scale. This study estimates the substantial effect land use and land cover changes can have on the land surface hydrological process in earth system modelling.