bluuebunny/crossref_metadata_2025 huggingface dataset:
Vulnerability assessment and Disaster Prevention Adaptation Planning Strategies for Industrial Parks
Authors: Pai Jen-Te , Chen Hong-Jie
Published: March 2020

In recent years, lots of major disasters happened in the industrial parks. As a critical infrastructure, it become an urgent issue to tackle the disaster prevention and vulnerability assessment of the industrial parks. This study reviews the theory of vulnerability, regional resilience, disaster prevention system for industrial parks and related literature to establish the vulnerability assessment framework. Therefore, by utilizing the fuzzy Delphi method to screen the indicators in four dimensions such as physical, social, exposure and economic, and also the AHP expert panel to set the related weights and the correlation between their indicators. And, follow up with Dynamic ANP Process to extract the decision-making structures in 2019, and 2030. In total, 63 industrial parks were evaluated by this evaluation framework and categorized by different vulnerable types. Therefore, responding disaster adaptation strategies were proposed for different parks as a reference for government.
Regional-residual separation of microgravity data based on data clustering
Authors: Rim Hyoungrea , Park Gyesoon , Kim Chang-Ryol
Published: March 2020

we propose a method to apply the polynomial fitting for regional-residual separation of microgravity data based on the characteristics of gravity anomaly without a prior information. Since the microgravity survey is usually carried out in small regions, it is common to approximate regional anomaly by the first-order polynomial plane. However, if the regional anomaly patterns are unsuited to be approximated to a first-order plane, the complete gravity anomaly is divided into small zones enough to approximate first-order plane by means of Parasnis density estimation method. The regional-residual separation is then applied on the splitted zones individually. When the gravity anomalies can be splitted spatially, we showed that the residual anomalies can be more effectively extracted based on the regional geological structures by regional anomaly separation from each of the divided regions, rather than applying the entire data set at one time.

Acknowledgment: This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2019R1F1A1055093).
A Multi-Scale Study of US Drought Awareness
Authors: Kam Jonghun
Published: March 2020

Big data have meaningful, but hidden, information about our society's behavior and response to influential events. Particularly, water-related disasters, such as drought and flood, cause rapid increase in public awareness/interest when they already happen. Despite the improved prediction skill, lack of timely social response to these disasters exacerbates economic losses and fatalities. 

In this presentation, I will introduce the utility of Google Trends data in monitoring and understanding the dynamic patterns of social response to drought at the state and national level. The first part of this presentation will show a case study of the dynamics of Californian awareness during the 2011–17 California Drought. The second part of this seminar will show a spatiotemporal analysis of US national drought awareness among the 49 US states. In closing, I will discuss the role of big data in transforming our society to a water-related disaster-ready environment.
Size-resolved hygroscopic behaviour and mixing state of submicron aerosols in a megacity of Sichuan Basin during pollution and fireworks episodesn during pollution and fireworks episodes
Authors: Yuan Liang
Published: March 2020

    In situ measurements are performed to study the size-resolved hygroscopic behaviour of submicron aerosols during pollution and fireworks episodes in winter from late January to February 2019 in Chengdu, a megacity in Sichuan Basin, using a humidity tandem differential mobility analyser (H-TDMA). The H-TDMA is operated at a relative humidity of 90% with dry aerosol diameters between 40 and 200 nm. Three modes of aerosol particles, including nearly hydrophobic mode (NH), less hygroscopic mode (LH), and more hygroscopic mode (MH), are found in the probability distributions of the growth factor (GF-PDF) during the campaign. The GF-PDF shows that aerosol particles are usually externally mixed. The average ensemble mean hygroscopicity parameter values (κMean) over the entire sampling period are 0.16, 0.19, 0.21, 0.23, and 0.26 for aerosols with diameters of 40, 80, 110, 150, and 200 nm, respectively. These averages are lower than those in Shanghai and Nanjing. κMean for aerosols larger than 110 nm, however, are higher than those in Beijing and Guangzhou during winter. Distinct diurnal patterns for all measured sizes are observed for the number fractions of the NH (NFNH) and MH (NFMH) modes as well as κ-PDF and κMean. The NFNH values are lower, but κMean exhibits peak values during daytime. More aerosols are internally mixed because of photochemical ageing during daytime. The number fraction of LH (NFLH) for the 40-nm diameter aerosols in clean periods (CPs) is larger than that in the pollution episode (PEs) because of the increasing amount of SOA formation. More aerosols of diameters larger than 80 nm are internally mixed during CPs and stage of contaminant accumulation, resulting in higher κMean values compared to those in PEs. The aerosol emissions of fireworks that accumulate during the Chinese New Year's Eve contribute to the slow and continuous increasing trend in κMean with average values of 0.19, 0.19, 0.21,0.23, and 0.27 for the 40, 80, 110, 150, and 200-nm diameter aerosols, respectively. These values are higher than those during the pre- and post-fireworks days. The hygroscopic properties of submicron aerosols in Chengdu are essential for understanding the formation and evolution of severe haze events in Sichuan Basin.
Evolution of Internal Solitary Waves on the Slope-shelf Topography in the Northern South China Sea
Authors: Wang Shuya , Li Qun , Chen Xu , Meng Jing , Li Saisai
Published: March 2020

Based on a non-hydrostatic two-dimensional and high-resolution model, evolution of internal solitary waves (ISWs) on the typical slope-shelf topography in the northern South China Sea is investigated numerically, and the influences of the initial amplitude, seasonal stratification and topographic characteristics are analyzed with a series of sensitivity runs. The results indicate that the initial amplitude affects the fission of ISW, resulting in three wave groups for large ISW and two wave groups for small ISW. In addition, the generation of mode-2 waves is influenced since energetic beams are engendered by large initial ISW, which impact the pycnocline and generate the mode-2 ISWs. Seasonal stratification has significant impacts on the evolution of the ISW. In winter, the changing sign of the nonlinearity coefficient at the bump near the shelf break implies the inversion of polarity of the ISW. Therefore, the transmitted and fissioned waves behave differently from those in summer and annual stratifications. Furthermore, the speed and energy of the leading wave are minimal in winter but maximal in summer. The bump near the continental shelf has two impacts: promoting the fission of the incident ISW and generating mode-2 ISWs by increasing the Ursell number (the ratio of nonlinear coefficient to dispersion coefficient). However, the formation of the trailing nonlinear wave packet is not affected by these factors, despite of the variations in detail in sensitivity runs.
Vertical Structures of Typical Meiyu Precipitation Events Retrieved from GPM‐DPR
Authors: Sun Yuting , Dong Xiquan , Cui Wenjun , Zhou Zhimin , Fu Zhikang , Zhou Lingli , Deng Yi , Cui Chunguang
Published: March 2020

The majority of heavy rainfall and flooding events in the central China during the Meiyu season are caused by the multi-scale monsoon frontal systems. However, there are limited studies of the vertical distributions of monsoon frontal rainfall. This work for the first time analyzed the vertical structures of the different stages of Meiyu precipitation systems over the Yangtze‐Huai River Valley in central China using measurements and retrievals from the Global Precipitation Measurement Mission Dual‐Frequency Precipitation Radar (GPM‐DPR) and Feng Yun satellites. GPM‐DPR retrieved near‐surface rain and drop size distributions were first validated against the surface disdrometer measurements and showed good agreement. Then we analyzed three cases from the Integrative Monsoon Frontal Rainfall Experiment to demonstrate the different characteristics of convective precipitation (CP) and stratiform precipitation (SP) in the developing, mature, and dissipating stages of the Meiyu precipitation systems, respectively. For statistical analysis, all Meiyu cases during the period 2016–2018 detected by GPM‐DPR were collected and classified into different types and stages. In the stratiform regions of Meiyu precipitation systems, coalescence slightly overwhelms break‐up and/or evaporation processes, but it was dominant in the convective regions when raindrops fall. There were large numbers of large ice particles during the developing stage due to strong updrafts and abundant moisture, whereas there were both large ice and liquid particles in the mature stage. The vertical structures of the SP examined in this study were similar to those over the ocean regions due to high relative humidity but different to the mountainous west regions of the USA. The findings of the stage‐dependent SP vertical structures provide better understanding of the evolution of monsoon frontal precipitation, as well as the associated microphysical properties, and provide insights to improve microphysical parameterization in future models.
A refined source apportionment study of atmospheric PM2.5 during winter heating period in Shijiazhuang, China, using a receptor model coupled with a source-oriented model
Authors: Liu Baoshuang , Zhang Yufen , Feng Yinchang , Dai Qili , Song Congbo
Published: March 2020

With the intensification of Chinese source control of air pollution, there is an urgent need for refined and rapid source apportionment techniques. A refined source apportionment method was constructed based on an off-line sampling dataset using a receptor model coupled with a source-oriented model, and the method was implemented in Shijiazhuang during the heating period. The refined results for source apportionment mainly included temporal, spatial, and source-category refinement data. The results indicated that the mean concentration of PM2.5 during the heating period was 96 μg/m3. Organic carbon (OC) and NO3- were found to be the dominant species of PM2.5 during the study. A high correlation was detected between elemental carbon (EC) and NO3– on polluted days, which was suggestive of the stagnant condition that accumulates EC and nitrate simultaneously. Secondary particle formation greatly promoted the occurrence of haze events. Secondary sources (34.9%), vehicle exhaust (18.6%), coal combustion (20.0%), industrial emissions (9.2%), crustal dust (9.7%), and biomass burning (7.6%) were the major sources during the heating period. The contributions of secondary sources and vehicle exhaust increased on polluted days, while those of coal combustion, industrial emissions and crustal dust decreased significantly. The contribution percentage of secondary sources from the southeast direction was basically the highest, while those of vehicle exhaust from the northwest or southeast directions were relatively higher as well, likely due to the distribution of traffic arteries. Based on the refined results for the source-category assessment, we found that the heating boilers (17.0%), non-road mobile (13.8%), diesel vehicles (10.4%), residential combustion (6.7%), road dust (5.5%), and architectural material industry (4.9%) were the major contributors to PM2.5. There was some uncertainty in the distribution proportions of the refined results, which were derived based on the emission inventory and the results of CALPUFF model.
Ground Test for Multispectral Camera of China’s First Mars Mission
Authors: liu dawei , liu jianjun , yan wei , zhang xiaoxia , liu donghao
Published: March 2020

China’s first Mars exploration mission will be launched in 2020 with an orbiter and a rover. Multispectral Camera (MC) is one payload onboard the rover. The main tasks of MC are to obtain multi-spectral images of the landing site and reconnaissance area of the rover, and to assess the mineralogy and composition of Mars surface. Multispectral imaging of MC is achieved via eight narrowband filters with their central wavelength at 480nm, 525nm, 650nm, 700nm, 800nm, 900nm, 950nm and 1000nm. The designed MC field of view is 24o and spatial resolution is higher than 0.15mrad.

In this study, we test two different experimental setups. The first one was dedicated to qualitatively evaluate the capabilities of MC in acquiring high quality images by observing the surface texture and structure of differing natural rocks at varying distance. The second one was to quantitatively assess the quality of the mineral spectra obtained by MC via comparison with that obtained simultaneously by a standard commercial equipment (ASD FieldSpec 4) under the same viewing geometry. The rock samples used for imaging capacity test include granite, rhyolite, basalt, andesite and peridotite. The mineral samples used for spectra quality evaluation include olivine, orthopyroxene, gypsum, chlorite, siderite and goethite. All these mineral and rock samples have been found on the Mars surface and are expected to be encountered when the rover reconnaissances.

Our results show that the images obtained by MC are quite clear. Detailed rock surface texture and structure such as vesicular and fluidal structure can be adequately captured by MC. RGB color composite image (R:650nm, G:525nm, B:480nm) of the rock targets generally consists with human perception. In addition, mineral spectra measured by MC agree well with that obtained by ASD. Absorption features of each mineral can be evidently revealed by the MC data, and the MC has the capacity to fully characterize the albedo and spectral shape of each mineral.
Transport and retention of nanoplastic particles in saturated columns packed with iron oxyhydroxide-coated sand
Authors: Lu Taotao , Gilfedder Benjamin S. , Frei Sven
Published: March 2020

With the increasing use of nanoplastic products in our daily life, these particles will invariably enter into the subsurface environment. It is, therefore, vital to understand the transport and retention of nanoplastic particles in groundwater systems. Surface charge heterogeneity is one of the basic chemical-physical characteristics of aquifer materials, but little research has been conducted on this topic. This study aimed to understand how the interaction between the porous media, solution chemistry, and NP surface charge influences the transport and retention of PS-NPs in the subsurface. 25 mg/L polystyrene nanoplastic particles (PS-NPs) were injected into columns packed with iron oxyhydroxide-coated sand. In addition, factors such as the content of iron oxyhydroxide-coated sand (λ), pH, ionic strength (IS), and cation valence were systematically studied. DLVO theory was used to evaluate the interactions between PS-NP and the porous media. By comparing the breakthrough curves (BTCs) of PS-NPs, it was clear that all these variables exerted a significant influence on the mobility of PS-NPs in the columns. These effects could be explained by the following: Firstly, by applying the DLVO theory, it was possible to model the electrostatic interaction between quartz sand and PS-NPs. For instance, at different IS (NaCl), the maximum energy barrier (Φmax) decreased with an increase in IS, which meant PS-NPs could more easily overcome the energy barrier to deposited on the sand surface at higher IS. Secondly, the positively charged iron oxyhydroxide coating provided additional favorable deposition sites for negatively charged PS-NPs. However, when the pH of the solution exceeded the iron oxyhydroxide pHpzc (~pH 9), the iron coating became negative and increased the mobility of PS-NPs. Finally, bridging agents, such as Ca2+ and Ba2+, resulted in the significant deposition of PS-NPs on the sand due to the bridging effect connecting the porous media and PS-NPs through the O-containing functional groups on both plastic and mineral surfaces. This study provides a better understanding of how the charge heterogeneity on aquifer materials and groundwater hydrochemistry affect the transport of PS-NPs in aquifers.
Sensitivity of phenology models to the selection of driving meteorological datasets
Authors: Dávid Réka Ágnes , Kern Anikó , Barcza Zoltán
Published: March 2020

Plant phenology focuses on the annual repetitive development phases of the terrestrial vegetation. Since the date of the onset and the cessation of vegetation growth define the possible time period for photosynthesis, plant phenology strongly affects the carbon cycle of the ecosystems. Phenology has a serious impact on the climate system through the carbon-, water- and energy cycle. Observations indicate changes in the phenological cycle of the vegetation worldwide that are clear indicators of climate change. Warming climate can be associated with more intense carbon uptake, but it can also negatively affect production. Current studies clearly indicated that the phenological cycle is not properly represented in the Earth System Models which means that further research is needed.

Meteorological variables affecting the state of the environment, such as temperature and precipitation, also play a key role in the development of vegetation. Phenology models of different complexity were developed to quantify the timing of the onset of vegetation growth based on meteorological data. The sensitivity of the models to the source meteorological datasets is rarely studied. The aim of the present study is to quantify the sensitivity of widely used phenology models to the selection of the driving meteorological dataset.

Two phenology models were used to evaluate the different databases. One is the so-called Growing Degree Day (GDD) method, which calculates the onset date based on the degree day logic. The GDD model is further divided into simple thermal forcing model and thermal model, where the latter includes chilling requirement as well. The second method uses minimum temperature, photoperiod and vapor pressure deficit and calculates a so-called Growing Season Index (GSI) which is used to estimate onset date

Considering the meteorological data, three different datasets were used. The ERA5 is a reanalysis database, which is the product of the European Centre for Medium-Range Weather Forecasts (ECMWF). The CarpatClim and the FORESEE (Open Database FOR ClimatE Change-Related Impact Sudies in CEntral Europe) are observation based, gridded datasets for the larger Carpathian Region (Central Europe).  

In any modelling exercise aiming at simulating the stages of phenology, observations are essential. In the present study the phenological observation data is originating from satellite data and field observations. The first means the third generation Normalized Vegetation Index (NDVI3g) disseminated by GIMMS (Global Inventory Modeling and Mapping Studies), and the latter means the PEP725 phenology dataset and field observations from the botanical garden of Eötvös Loránd University, located in Budapest.
Investigation of cloud radiative effects and closure in the Central Arctic based on ship-borne remote sensing observations
Authors: Barrientos Velasco Carola , Deneke Hartwig , Ehrlich Andre , Gottschalk Matthias , Griesche Hannes , Hünerbein Anja , Seifert Patric , Stapf Johannes , Macke Andreas
Published: March 2020
Temporal gravity variations in GOCE release 6 gravitational gradients
Authors: Heller Betty , Siegismund Frank , Pail Roland , Gruber Thomas
Published: March 2020

As opposed to the level 1B release 5 GOCE gravitational gradient data, the newly reprocessed release 6 gradients provide reduced noise amplitudes in the low frequency-range, leading to reduced noise amplitudes of the derived gravity field models at large spatial scales, where temporal variations of the Earth’s gravity field have their highest amplitudes. This is the motivation to test the release 6 gradients for their ability to resolve temporal gravity variations.

For the gravity field processing, we apply a conventional spherical harmonics approach using the time-wise (TIM) processing method as well as a mass concentration (mascon) approach using point masses as base elements, which are grouped to land or ocean mascons by taking into account the coastlines.

By means of a closed-loop simulation study, we find that the colored instrument noise of the GOCE gravitational gradiometer introduces noise amplitudes into the derived gravity field models that lie above the amplitude of the gravity trend signal accumulated over 5 years. This indicates that detecting gravity variations taking place during the four-year GOCE data period from GOCE gradients only is challenging.

Using real GOCE data, we test bimonthly gradiometry-only gravity field models computed by both the spherical harmonic and the mascon approach for gravity signals that are resolved by GRACE data, being the temporal signals due to the ice mass trends in Greenland and Antarctica and the 2011 earthquake in Japan. Besides, corresponding GRACE/GOCE combination models are used to test whether the incorporation of GOCE data increases the resolution of temporal gravity signals.

We found that high-amplitude long-wavelength noise prevented the detection of temporal gravity variations among the bimonthly GOCE-only models. Using the SH approach, it was possible to detect the mean trend signal contained in the data by averaging multiple bimonthly models and considering their difference to a reference model. Using the mascon approach, trend signals contained in GOCE data could be recovered by including a GRACE model truncated to d/o 45 in a GRACE/GOCE combination model and thus let the GOCE data determine the short-scale signal structures instead of GRACE.

Finally, compared to the temporal gravity signal as resolved by GRACE data, no significant benefit of using or incorporating GOCE gravitational gradient data was found. The reason are the still rather high noise amplitudes in the derived models at large spatial scales, where the considered signal is strongest.

In order to detect temporal gravity variations in satellite gravitational gradiometry data, the measurement noise amplitudes in the low-frequency range would need to be reduced.
Aerosol-cloud interactions from combined observations with geostationary and polar-orbiting sensors
Authors: Tesche Matthias , Seelig Torsten , Alexandri Fani , Bräuer Peter , Choudhury Goutam , Hu Yuanyuan , Quaas Johannes
Published: March 2020

Atmospheric aerosol particles are of great importance for cloud formation in the atmosphere because they are needed to act as cloud condensation nuclei (CCN) in liquid-water clouds and as ice nucleating particles (INP) in ice-containing clouds. Changes in aerosol concentration affect the albedo, development, phase, lifetime and rain rate of clouds. These aerosol-cloud interactions (ACI) and the resulting climate effects still cause the largest uncertainty in assessing climate change as they are understood only with medium confidence.

The PACIFIC project, which is embedded in the French-German Make Our Planet Great Again (MOPGA) initiative, aims to improve our understanding of ACI by enhancing the representation of those aerosols that are relevant for cloud processes and by quantifying temporal changes in cloud properties throughout the cloud life cycle. PACIFIC uses a three-fold approach for studying ACI based on spaceborne observations by (i) using spaceborne lidar data to obtain unprecedented insight in CCN and INP concentrations at cloud level opposed to using column-integrated parameters, (ii) characterizing the development of clouds by tracking them in time-resolved geostationary observations opposed to resorting to the snap-shot view of polar-orbiting sensors, and (iii) combining the detailed observations from polar-orbiting sensors with the time-resolved observations of geostationary sensors – for clouds observed by both – to study the effects of CCN and INP on the albedo, liquid and ice water content, droplet and crystal size, development, phase and rain rate of clouds within different regimes carefully accounting for the meteorological background.

This contribution will present the scope of the MOPGA-GRI project PACIFIC and illustrate the first findings.
The impacts of residual layer on the vertical distributions of pollutant particulate matter: combining large tethered balloon and remote sensing observations
Authors: Yu Shi , Hu Fei , Sun Haijiong , Zhang Zhe , Ding Weichen
Published: March 2020

The combination of in situ observations from a large tethered balloon and remote sensing instruments (aerosol lidar and Doppler wind lidar) enabled the evolution of the residual layer (RL) to be observed during an intensive vertical detection experiment of the planetary boundary layer (PBL) conducted during December (Dec) 2018 in Wangdu County, China. This paper focused on the important role played by the RL in the variations of the vertical distributions of pollutant particulates. The results of the present analysis revealed the following. (1) A considerable proportion of pollutant particulates remained suspended in the RL (e.g., the nitrate concentration reached 30 µg m-3) in the nocturnal boundary layer (NBL). Multilayer pollutant structures appeared often, partly because of the existence of the RL. Because pollutants were still stored in the RL and the shallow surface inversion layer, the aerosol lidar-calculated PBL height was closer to the top of the RL before midnight in the NBL; after midnight, the PBL height was more consistent with the top of the surface inversion layer. (2) As the convective mixing layer gradually became established after sunrise the following day, the pollutants stored in the nocturnal RL of the preceding night were entrained downward into the mixing layer. The early morning PM2.5 concentration near 700 m in the RL on Dec 20 decreased obviously compared with the concentration at 13:34 on Dec 20 at the same height (ranging from 30 µg m-3 to 5 µg m-3). The nitrate concentration also decreased significantly in the RL, but its concentration increased to 12 µg m-3 in the mixing layer. Near-surface PM2.5 diffused upward more easily due to strong vertical mixing during the daytime, causing reductions in the surface concentration. The mixing layer heights in Wangdu County were estimated to be 600 m in the winter, and various emitted pollutant particulates eventually became well-mixed within the mixing layer. The daytime mixing layer heights were consistent with the PBL heights calculated by aerosol lidar representing the pollutant accumulation depth. (3) The RL was characterized by a Richardson number (Ri) below the threshold value of 0.25, revealing that turbulence still existed within the RL.
Mantle Flow Trajectories in the Presence of Poorly Constrained Initial Conditions: Analysis of an Ensemble of Models
Authors: Taiwo Ayodeji , Bunge Hans-Peter
Published: March 2020

A crucial goal in geodynamics is the development of time-dependent earth models so that poorly known mantle convection parameters can be tested against observables gleaned from the geologic record. To this end one must construct model trajectories to link estimates of the current heterogeneity state to future or past flow structures via forward or inverse mantle convection models. Unfortunately, the current heterogeneity state which is derived from seismic imaging methods is subject to substantial uncertainty due to the finite resolution of seismic tomography. These uncertainties are likely to considerably affect the computed flow trajectory, in what is known as the butterfly effect. Here we study mantle convection models to assess the effects of varying initial conditions on the evolution of mantle flow. We compute convection calculations with identical flow parameters but different initial temperature fields. A base temperature field is generated by allowing a mantle convection calculation to evolve until a statistical steady state is reached. This temperature field is then used to initialize our reference case. We proceed to modify this reference temperature field in three different forms to reflect tomographic choices of damping and smoothing: in the first case, we apply a radial averaging to the reference temperature field. In the second case, we truncate a spherical harmonic expansion of the reference field at degree 20. In the final case, we apply an S20RTS filter to the reference field. In all cases we track the divergence of the perturbed models from the reference model. Furthermore, we test the efficiency of surface velocity assimilation, following from the work of Colli et al(2015), in locking two convecting systems and driving their divergence to a minimum. We find in all experiments that the divergence grows exponentially before hitting a maximum value, within 4 transit times, at which point it ceases to grow. In addition, surface velocity assimilation leads either to a reduction of the divergence or prevention of its further growth and within 3 transit times, the maximum possible convergence between reference and perturbed models is reached for all cases, further confirming the results seen in Colli et al(2015).
Sediment origins across the terrestrial-aquatic continuum: climate threat mitigation and promotion of water quality
Authors: Wiltshire Katy , Waine Toby , Grabowski Bob , Glendell Miriam , Addy Steve , Baggaley Nikki , Thornton Barry , Meersmans Jeroen , Napier Fiona
Published: March 2020

Although fine-grained sediment (FGS) is a natural component of river systems, increased fluxes can impact FGS levels to such an extent they cause detrimental, irreversible changes in the way rivers function intensifying flood risk and negatively affecting water quality.

Previous catchment scale studies indicate there is no simple link between areas of sediment loss and the organic carbon (OC) load in waterways; areas with a high soil loss rate may not contribute most sediment to the rivers and areas that contribute the most sediment may not contribute the most OC. Anthropogenic and climate changes can accelerate soil erosion and the role of soil OC transported by erosional processes in the fluxes of C between land, water and atmosphere is still debated. Tracing sediment pathways, likely depositional areas and connections to streams leads to better assumptions about control processes and better estimation of OC fluxes.

In this innovative study OC fingerprinting of sediment reaching a catchment’s waterbodies is combined with OC stock and erosion modelling of the terrestrial catchment. Initial results show disconnect between catchment OC loss erosion modelling and fingerprinting results, which could be due to failure to model connectivity between the land and river channel. The current soil erosion model RUSLE (Revised Universal Soil Loss Equation) calculates only the spatial pattern of mean annual soil erosion rates. Using the WaTEM SEDEM model, which in includes routing (and possible en route deposition) of eroded sediments to river channels, we aim to determine the dominant source of OC within catchment streams by identification of both the land-use specific areas with the highest OC loss and the transport pathways between the sources and river channel.
Modelling gravity-driven fingering in soils having an intrinsic non-zero contact angle (water repellent soils) using the innovative moving-boundary approach
Authors: Wallach Rony , Brindt Naaran
Published: March 2020

Quantitative and Qualitative description of infiltration into soils in general and initially dry soils in particular those in which the hydraulic properties vary spatial and temporal have been challenging soil physicists and hydrologists. Water repellent soils, whose contact angle is higher than 40° and can even reach values that are greater than 90° (noted as hydrophobic soils) are an example of such challenge cases. Infiltration in these soils takes usually place along preferential flow pathways (noted as gravity-induced fingering), rather than in a laterally uniform moving wetting front. The water content and capillary pressure distributions along these fingers are non-monotonic with water accumulation behind the moving wetting front (noted as saturation overshoot) and a decreasing water content toward the soil surface. Being a parabolic-type partial differential equation, the Richards equation that is commonly used to model flow in soils can't handle such water content/pressure distributions. Many attempts have been made to modify the Richards equation to enable it to model the non-monotonic water content profiles. These attempts that are not based on the measurable soil properties that can highlight the physics that induces the formation of such non-monotonic distribution.  

A new conceptual modelling approach, noted as the moving-boundary approach, will be presented. This approach overcomes the existing theoretical gaps in the quantitative descriptions that have been suggested for the non-monotonic water content distribution in the gravity-induced fingers. The moving-boundary approach is based on the presumption that non-monotonicity in water content is formed by an intrinsic higher-than-zero contact angle. Note that non-zero contact angle have been rarely incorporated in models used for quantifying infiltration into field soils, in spite of the findings that most soils feature some degree of repellency. The verified moving-boundary solution will be used to demonstrate the synergistic effect of contact angle and incoming flux on the stability of 2D flow and its associated plume shapes. The physically-based moving-boundary approach fulfils several criteria raised by researchers to adequately describe gravity-driven unstable flow.

 
The Plasmasphere During Major Geomagnetic Storms: Analysis Of Trapped Particles In The Outer Radiation Belt
Authors: Matar Jessy , Hubert Benoit , Cowley Stan , Milan Steve , Yao Zhonghua , Guo Ruilong , Goldstein Jerry , Sandel Bill
Published: March 2020

 The coupling between the Earth’s magnetic field and the interplanetary magnetic field (IMF) transported by the solar wind results in a cycle of magnetic field lines opening and closing generally known as the Dungey substorm cycle, mostly governed by the process of magnetic reconnection. The geomagnetic field lines can therefore have either a closed or an open topology, i.e. lower latitude field lines are closed (map from southern ionosphere to the northern), while higher latitude field lines are open (map from one polar ionosphere into interplanetary space). Closed field lines can trap electrically charged particles that bounce between mirror points located in the North and South hemispheres while drifting in longitude around the Earth, forming the plasmasphere, the radiation belts and the ring current. The outer boundary of the plasmasphere is the plasmapause. Its location is mostly driven by the interplay of the corotation electric field of ionospheric origin, and the convection electric field that results from the interaction between the IMF and the geomagnetic field. At times of prolonged intense coupling between these fields, the response of the magnetosphere becomes global and a geomagnetic storm develops. The ring current created by the motion of the trapped energetic particles intensifies and then decays as the storm abates. This study aims to find a possible relationship between the evolution of the trapped population and the process of magnetic reconnection during storm times. The EUV instrument on board the NASA-IMAGE spacecraft observed the distribution of the trapped helium ions (He+) in the plasmasphere. We consider several cases of intense geomagnetic storms observed by the IMAGE satellite. We identify the plasmapause location (Lpp) during those cases. We find a strong correlation between the Dst index and Lpp. The ring current and the trapped particles are expected to vary during storms. We use the Tsyganenko magnetic field model to map the electric potential between the Heppner-Maynard boundary (HMB) in the ionosphere and the magnetosphere and estimate the voltage and electric field in the vicinity of the plasmapause. The ionospheric electric field is deduced from the ionospheric convection velocity measured by the SuperDARN (SD) radar network at high latitudes. The tangential electric field component of the moving plasmapause boundary is estimated from IMAGE-EUV observations of the plasmasphere and is compared with expectations based on the SD data. We combine measurements of the trapped population from IMAGE-EUV and IMAGE-FUV observations of the aurora to better understand and quantify the variability of the Earth's outer radiation belt during strong storms. The auroral precipitation at ionospheric latitude is studied using FUV imaging and compared to the He+ response during the storms.
On spreading modes and magma supply at slow and ultraslow mid-ocean ridges
Authors: Cannat Mathilde
Published: March 2020

 

The availability of magma is a key to understand mid-ocean ridge tectonics, and specifically the distribution of the two contrasted spreading modes displayed at slow and ultraslow ridges (volcanically-dominated, and detachment fault-dominated). The part of the plate divergence that is not accommodated by magma emplaced as gabbros or basaltic dikes is taken up by normal faults that exhume upper mantle rocks, in many instances all the way to the seafloor.

Magma is, however, more than just a material that is, or is not, available to fill the gap between two diverging plates. It is the principal carrier of heat into the axial region and as such it may contribute to thin the axial lithosphere, hence diminishing the volume of new plate material formed at each increment of plate separation. Magma as a heat carrier may also, however, if emplaced in the more permeable upper lithosphere, attract and fuel vigorous hydrothermal circulation and contribute instead to overcooling the newly formed upper plate (Cochran and Buck, JGR 2001).

Magma is also a powerful agent for strain localization in the axial region: magma and melt-crystal mushes are weak; gabbros that crystallize from these melts are weaker than peridotites because they contain abundant plagioclase; and hydrothermally-altered gabbros, and gabbro-peridotite mixtures, are weaker than serpentinites because of minerals such as chlorite and talc. As a result, detachment-dominated ridge regions that receive very little magma probably have a stronger axial lithosphere than detachment-dominated ridge regions that receive a little more magma.

Because magma has this triple role (building material, heat carrier, and strain localization agent), and because it is highly mobile (through porosity, along permeability barriers, in fractures and dikes), it is likely that variations in magma supply to the ridge, in time and space, and variations in where this magma gets emplaced in the axial plate, cause a greater diversity of spreading modes, and of the resulting slow and ultraslow lithosphere composition and structure, than suggested by the first order dichotomy between volcanically-dominated and detachment-dominated spreading.

In this talk I illustrate these points using results of recent studies at the Mid-Atlantic and Southwest Indian ridges.
Georadar survey to explore a supposed ejecta layer around the Maâdna crater (Talemzane, Algeria)
Authors: Hamai Lamine , Lamali Atmane , Yelles-chaouche Abdelkrim , Abtout Abdeslam , Nadjemi Abdelmadjid , Merabet Nacer-Eddine , Bentridi Salah-Eddine , Djadia Leila , mokhtar Sid Ahmed
Published: March 2020

Geophysics continues to play a critical role in the future discovery of terrestrial impact structures. While the signatures within these structures may not be unique, the application of geophysics can effectively characterize them, even when they are deeply eroded or completely buried underground. In the case of Maâdna crater (33°19' N, 4°19' E), among new performed geophysical surveys, a GPR technique has been especially used to explore a supposed ejecta layer. However, GPR survey results allowed the confirmation of nonexistence of such as melting materials at Maâdna crater. Nevertheless, our different scans were interpretative against the structural context of the Maâdna structure. Indeed, most of the analyzed profiles allowed us recognizing the typical deformation effects at this structure, which can also generally be encountered at any crater-like structured site. Consequently, in view to this new resulting GPR data, even we do not definitely reject an impact origin, we are still pleading for other caratering scenarios for this structure.
Relative dispersion in a model of stratified upper-ocean turbulence
Authors: Berti Stefano , Lapeyre Guillaume
Published: March 2020

Turbulence in the upper ocean in the submesoscale range (scales smaller than the deformation radius) plays an important role for the heat exchange with the atmosphere and for oceanic biogeochemistry. Its dynamical features are thought to strongly depend on the seasonal cycle and the associated mixed-layer instabilities. The latter are particularly relevant in winter and are responsible for the fomation of energetic small scales that are not confined in a thin layer close to the surface, as those arising from mesoscale-driven processes, but extend over the whole depth of the mixed layer. The knowledge of the transport properties of oceanic flows at depth, however, is still limited, due to the complexity of performing measurements below the surface. Improving this knowledge is essential to understand how the surface dynamics couple with those of the ocean interior.

By means of numerical simulations, here we explore the dispersion properties of turbulent flows in a quasi-geostrophic model system made of two coupled fluid layers (aimed to represent the mixed layer and the thermocline) with different stratification. Such a model has been previously shown to give rise to dynamics that compare well with observations of wintertime submesoscale flows. We examine the horizontal relative dispersion of Lagrangian tracers by means of both fixed-time and fixed-scale statistical indicators, at the surface and at depth, in the different dynamical regimes occurring in the presence, or not, of a mixed layer. The results indicate that, when mixed-layer instabilities are present, the dispersion regime is local (meaning governed by eddies of the same size as the particle separation distance) from the surface down to depths comparable with that of the interface with the thermocline. By contrasting this picture with what happens in the absence of a mixed layer, when dispersion quickly becomes nonlocal (i.e. dominated by the transport by the largest eddies) as a function of depth, we identify the origin of this behavior in the existence of fine-scale energetic structures due to mixed-layer instabilities. Finally, we discuss the effect of vertical shear on the tracer spreading process and address the correlation between the dispersion properties at the surface and in deeper layers, which is relevant to assess the possibility of inferring the dynamical features of deeper flows from the more accessible surface ones.
Analyzing earthquakes and hybrid events on Fogo and Brava, Cape Verde, with multiple arrays
Authors: Leva Carola , Rümpker Georg , Wölbern Ingo
Published: March 2020

Fogo and Brava are part of the south-western chain of the Cape Verde archipelago, which is believed to originate from a mantle plume. The two islands are located about 18 km apart from each other. Only Fogo experienced historic eruptions at intervals of about 20 years, with the last eruption from November 2014 to February 2015. In contrast to Fogo, Brava shows a high seismic activity. In our study we focus on the characterization of the seismicity in the region. We employ multi-array techniques to study the seismic activity, as many events are located offshore. Additionally, arrays are well suited for the analysis of volcano-related seismic signals without clear onset of phases. From January 2017 to January 2018 we operated a network of three seismic arrays (two on Fogo, one on Brava) and seven single short-period stations (five on Fogo, two on Brava). The arrays consist of 4 broad-band and 6 short-period stations each and are shaped circularly with an aperture of approximately 700 m. We apply a time-domain array analysis to locate seismic events. This approach is computationally more expensive than a traditional f-k analysis, but allows for a higher flexibility in the selection of relevant time windows to calculate the beam energy. For the analysis in the time-domain, traces are first shifted and then cut to suitable time windows to determine the energy stack as a function of horizontal slowness.

For a single array, epicentral distances can be estimated from arrival-time differences between S- and P-waves, by assuming a suitable velocity structure. However, with two or more arrays, epicenters can be obtained directly from the intersecting beams. The technique is applied to earthquakes as well as to hybrid events. During 2017 the seismicity is clearly dominated by volcano-tectonic earthquakes, mainly originating beneath and around Brava. Additionally we observe hybrid events on Fogo, which are characterized by a transition from high (20-40 Hz) to low (1-10 Hz) frequencies. The events lack clear phases, although they often exhibit a relatively sharp onset. These features provide ideal conditions for the application of the multi-array analysis. The hybrid events originate in the Chã das Caldeiras region, a collapse scar surrounding the present-day Fogo volcano, and are likely related to rock-fall events.
Lagged ensemble vs burst sampling strategy for initializing sub-seasonal forecasts
Authors: Vitart Frederic
Published: March 2020

The WWRP/WCRP Sub-seasonal to Seasonal Prediction (S2S) database contains real-time and re-forecasts from 11 operational centres. Several S2S models are initialized frequently with a small ensemble size (e.g. 4 ensemble members every day). In order to inflate the ensemble size, real-time forecasts are produced by combining all the forecasts produced over a window of several days to produce a “lagged ensemble” in which ensemble members have different lead times. The other S2S models are initialized less frequently (e.g. once or twice a week) but with a large ensemble size (e.g. 51 members). This initialization strategy is referred to as “burst sampling”. Both strategies have advantages and inconvenience and it is not clear which strategy is optimal for sub-seasonal prediction. 
The ECMWF sub-seasonal forecasts are produced using the burst-sampling strategy: a 51-member ensemble is run twice a week (every Monday and Thursday). A large set of re-forecasts, run on a daily basis, have been produced to assess the potential benefit of replacing this current ensemble configuration by a lagged-ensemble approach. We are interested in answering the following two questions, if the current 51-member ensemble run twice a week is replaced by a sub-seasonal ensemble run every day with an ensemble size Ne:

• What is the minimum value of Ne so that there is a lagged ensemble forecast (Nd forecast days combined) which is at least as skilful as the current system on Mondays and Thursdays?

• For a given value of Ne, what is the optimal number Nd of forecast days to combine? Greater values of Nd produce larger lagged ensemble size, but also reduce the accuracy of the forecasts by adding ensemble members with older start dates. 

Results indicate that:

1. A lagged ensemble is more beneficial in the Tropics than in the Northern Extratropics particularly for shorter lead times (weeks 1 and 2).  

2. The minimum daily ensemble size to produce sub-seasonal forecasts (beyond week 1) at least as skilful as the current ECMWF forecasts on Mondays and Thursdays is Ne=20 with an optimal number of lag days Nd=3. The values of Ne (Nd) decrease (increase) with increased lead time. 

These results suggest that a lagged-ensemble could be a viable alternative to the current ensemble extended-range forecasting system at ECMWF. 