bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of changes in soil erosion rates in Andalucia between 1990 and 2018
Authors: Milazzo Filippo , Vanwalleghem Tom , Fernández, Rebollo Pilar , Fernández-Habas Jesus
Published: March 2020

Land use and land management changes impact significantly on soil erosion rates. The Mediterranean, and in particular Southern Spain, has been affected by important shifts in the last decades. This area is currently identified as a hotspot for soil erosion by water. In the effort to achieve the SDG Target 15, we aim to show the effect of land management change, assessing soil erosion rate based on historical data. We analyzed the evolution of land use from historical aerial photographs between 1990 and 2018. We then calculated soil erosion with RUSLE. For this, we first determined the distribution frequency of cover-management factors for each land use class, comparing current land use maps with the European Soil Erosion Map (Panagos et al., 2015). Past C factors where then assigned using a Monte Carlo approach, based on the obtained frequency distributions. 
Quantifying net irrigation across the North China Plain through dual modelling of evapotranspiration
Authors: Koch Julian , Stisen Simon , He Xin , Martinsen Grith
Published: March 2020

Knowledge of irrigation water use is crucial for ensuring food and water security in water scarce regions. Even though irrigation is one of the most important direct human interferences with the terrestrial water cycle, there exists limited knowledge on the extent of irrigated areas and in particular the amount of water applied for irrigation. In this study, we develop a novel approach that estimates net water loss due to irrigation and apply it over the North China Plain domain, which is a global hotspot for severe groundwater depletion caused by extensive irrigation practices. Our goal is to retrieve spatio-temporal patterns of net irrigation amounts, constituted as evaporative loss of irrigated water, at monthly timescale at 1km2 spatial resolution. The analysis is based on a direct comparison of two alternative evapotranspiration (ET) models: (1) A remote sensing based model (PT-JPL-thermal) using various MODIS products as input and (2) a one-dimensional, free drainage hydrological model (mHM). The hydrological model is purely driven by rainfall and will therefore naturally show a strong disagreement with the remote sensing based ET during periods of extensive irrigation. We use this systematic residual term that reflects a non-precipitation-based water source, as quantification of net irrigation. The hydrological model is calibrated against the remote sensing based ET at grids that are not affected by irrigation and discharge records representing natural flow. Total water storage anomalies retrieved by GRACE are utilized to evaluate the derived net irrigation amounts over the North China Plain. We find, that irrigation peaks in May, which corresponds to the peak of the growing season of winter wheat. Moreover total irrigation amounts to 116 mm per year (14km3), which is in good agreement with previous studies. The net irrigation estimates are at an unprecedented spatial and temporal resolution and are extremely valuable input for water resources management as well as for subsequent groundwater modelling where net irrigation can be utilized as pumping boundary condition.
Rate and State Seismicity Simulations for Large Earthquake Cycles in Western Taiwan
Authors: Wu Hung-Yu , Ma Kuo-Fong , Fry Bill
Published: March 2020

The stress state variation during the fault rupturing is the key issue for the earthquake hazard. However, the modern seismic catalogs exist the huge gap of large earthquake recurrence records. To understand the occurrence, the probabilities and the dynamic processing of large earthquakes, we employed the multi-cycle earthquake simulator, RSQSim, to exam the fundamental aspects of seismicity distribution in spatial and time in western Taiwan. This 3D, boundary element software assembles the Rate and State Friction law (RSF) and initial stress state to simulate the earthquakes distributions in completely, complex seismogenic system. The heterogeneous initial stresses and recurrence seismic events would be estimated in the long sequences. In this research, we focus on the similarity comparison to the CWB earthquake catalog and Taiwan Earthquake Model (TEM) for the RSQSim simulations. Additionally, this information provides the near optimal nucleation locations and seismic events propagation at the stress evolution in Taiwan faulting systems. Through this process, we would like to examine the recurrence time of the significant earthquakes in western Taiwan. RSQsim results include the comprehensive large events in temporal series to understand the key discrepancy between models and simulators, which will bring the mutual input to TEM for update discussion on slip rate, stress accumulation, and fault system. These modifications provide the better understanding of faults slip and stress state evolution to support the fundamental aspects of earthquake cycles.
Last 12 ky record of various organic geochemical proxies in the Eastern Arabian Sea
Authors: Manaskanya Ayusmati , Mazumdar Aninda , Peketi Aditya , Fernandes Svetlana , Silva Rheane D. A.
Published: March 2020

Here we present high-resolution biogeochemical study using nitrogen/carbon isotope ratio measurement and molecular proxies from a sediment core (length = 2.9 m) collected from the center (588 mbsl; Lat: 16049.88’N and Long: 710 58.55’ E) of the oxygen minimum zone off west coast of India. The core archives the depositional record covering 1.114 to 12.025 ky BP. The concentrations of total organic carbon (TOC) and total nitrogen (TN) range from 0.7 to 4.9 wt% and 0.068 to 0.5 wt % respectively. TOC and TN show parallel trends and the TOC/TN ratio varies within a narrow range of 8 to 11.5. The δ13C values range from -20.5‰ to -21.9‰ (V-PDB). The TOC/TN and δ13C suggest typical marine organic matter source. This observation is also further supported by the n-alkane distribution pattern where the dominance of nC21 to nC24 and the absence of odd alkane dominance over even suggest predominantly marine organic source. The δ15N profile shows a steady increase from 5.7‰ at 203 cmbsf (5.5 ky BP) to 7.5‰ at 2 cmbsf (~1ky BP) suggesting gradual increase in denitrification possibly liked to reduced ventilation in the Arabian Sea, whereas, between 5.5 to 12 ky BP, the δ15N values show marked fluctuations (5.2 to 7.1‰) possibly indicating variable level of oxygenation which in turn controlled the extent of denitrification. Possible influence of diagenesis (microbial degradation of organic matter) on the δ15N values also need to be investigated for a better understanding of the water column processes.
Study on the influence of seasonal frozen thawing process on the surface flux in the Loess Plateau
Authors: li zhenchao
Published: March 2020

The effects of soil seasonal freezing and thawing process on land surface heat fluxes were analyzed with two years observation data from 2013 to 2014 . The results showed that the sensible heat, latent heat and soil heat flux have no change significantly during the soil freezing stage. The sensible heat flux increased significantly, the latent heat flux decreased significantly, and the corresponding wave ratio increased during the frozen period. The soil moisture and soil heat flux increases rapidly, sensible heat flux and surface long wave radiation decrease rapidly, latent heat flux increases rapidly during the thawing stage. The thawing process of frozen soil has an obvious effect on the heat flux of soil, which increases the heat flux from surface soil to deep soil because of that the heat absorption of ice in thawing process.
Spatial and temporal scales of variability in the Meghna estuary from ocean remote sensing
Authors: Chowdhury Masuma , Laiz Alonso Irene , Caballero de Frutos Isabel
Published: March 2020

Abstract

Meghna Estuary is a very complex and dynamic estuarine system because of its irregular shape, wide seasonal variation and the changing role of tides. Every year, a major portion of the flow laden with high amount of sediments from the Ganges-Brahmaputra-Meghna river system are transferred through this estuary to the Bay of Bengal (BoB). The purpose of this analysis is to extract the dominant patterns of satellite Chlorophyll-a (CHL), Total Suspended Matter (TSM) and Sea Surface Temperature (SST) variability off the Meghna Estuary. CHL and TSM data were downloaded from GlobColour Project (http://globcolour.info/) and SST data were downloaded from Ocean Colour Project (https://oceancolor.gsfc.nasa.gov) using the monthly, 4km resolution of the global earth domain over eleven years (April 2002-April 2012). A temporal Empirical Orthogonal Function (EOF) analysis was performed to all the variables. The results revealed that the mean spatial distribution of the selected environmental variables in the Meghna estuary and its adjacent area during the study period showed clear latitudinal patterns in case of CHL and TSM, with higher values around the northern coast and a gradual offshore decreasing gradient. The SST map showed the same spatial pattern but with lower temperature values around the northern coastal fringe and higher values offshore. Only the first EOFs mode was found to be relevant, representing 25.55%, 15% and 89.43% of the CHL, TSM and SST variance, respectively, and depicted that the seasonal variability is the dominant pattern in this complex estuarine environment.
Impact of wave-induced sea ice fragmentation on sea ice dynamics in the MIZ
Authors: Boutin Guillaume , Williams Timothy , Rampal Pierre , Olason Einar , Lique Camille
Published: March 2020

The decrease in Arctic sea ice extent is associated with an increase of the area where sea ice and open ocean interact, commonly referred to as the Marginal Ice Zone (MIZ). In this area, sea ice is particularly exposed to waves that can penetrate over tens to hundreds of kilometres into the ice cover. Waves are known to play a major role in the fragmentation of sea ice in the MIZ, and the interactions between wave-induced sea ice fragmentation and lateral melting have received particular attention in recent years. The impact of this fragmentation on sea ice dynamics, however, remains mostly unknown, although it is thought that fragmented sea ice experiences less resistance to deformation than pack ice. In this presentation, we will introduce a new coupled framework involving the spectral wave model WAVEWATCH III and the sea ice model neXtSIM, which includes a Maxwell-Elasto Brittle rheology. We use this coupled modelling system to investigate the potential impact of wave-induced sea ice fragmentation on sea ice dynamics. Focusing on the Barents Sea, we find that the decrease of the internal stress of sea ice resulting from its fragmentation by waves results in a more dynamical MIZ, in particular in areas where sea ice is compact. Sea ice drift is enhanced for both on-ice and off-ice wind conditions. Our results stress the importance of considering wave–sea-ice interactions for forecast applications. They also suggest that waves likely modulate the area of sea ice that is advected away from the pack by ocean (sub-)mesoscale eddies near the ice edge, potentially contributing to the observed past, current and future sea ice cover decline in the Arctic. 
Geological data incorporation into an opportunities model for Irish offshore wind energy to inform engineering considerations and habitat change potential
Authors: Peters Jared , O’Connell Ross , Wheeler Andrew , Cummins Valerie , Murphy Jimmy
Published: March 2020

The implications of climate change are becoming harder to ignore and highlight the need for increased renewable energy production.  Simultaneously, technological developments like larger turbines and floating foundations are improving our ability to harvest offshore wind energy as a renewable resource.  However, despite having an abundant offshore wind energy resource, Ireland is falling behind on its remit to reduce its carbon emissions as part of the European Union’s targets outlined by the 2030 Climate and Energy Framework.  Reducing this inaction is critically important and improvements to Irish renewable energy planning could also be adapted to other locations.  Here we present spatial data rasters created largely from public datasets that have been designed to improve initial planning and opportunities assessments for Irish offshore wind development.  These rasters include information on surficial sediment types, geomorphology, and slope, which are typically not included in preliminary offshore renewable energy assessments despite their importance to turbine foundation designs, scour protection measures, and cable routes.  Furthermore, these rasters allow fundamental predictions on potential benthic habitat changes to be included into site selection models, which could help avoid economically and/or environmentally costly development decisions.  We examine potential uses for these rasters within a multi-criteria decision analysis and discuss the implications of incorporating such geological data during early investigations. 
Grad-Shafranov reconstruction of the in-plane magnetic field potential in the X-point vicinity: boundary-layer approximation
Authors: Korovinskiy Daniil , Divin Andrey , Semenov Vladimir , Erkaev Nikolai , Kiehas Stefan
Published: March 2020

The problem of steady symmetrical two-dimensional magnetic reconnection is addressed in terms of the EMHD approximation. In the immediate vicinity of the X-point, this approach has been proven to be an appropriate frame for the reconstruction problem, expressed, particularly, by the Poisson equation for the magnetic potential A, where the right-hand side contains the out-of-plane electron current density with reversed sign. With boundary conditions fixed at some curve (the satellite trajectory), and assuming the right-hand side to be a function of A, one arrives at an ill-posed problem for the Grad-Shafranov equation. The further simplification of the problem may be achieved by using the boundary layer approximation, since magnetic configuration in reconnection region is highly stretched. The benchmark reconstruction of PIC-simulation data, using four numerical techniques, has shown that the main contribution for inaccuracy arises from replacing the Poisson equation by the Grad-Shafranov one. A boundary layer approximation, in turn, does not affect the accuracy significantly; in some cases this approach can appear even the most appropriate. 
Rift-basin compartmentalization and changing environments: tectono-climatic forcing of environmental conditions and species dispersal in the East African Rift System (EARS)
Authors: Strecker Manfred R , Dommain René , Garcin Yannick , Olaka Lydia A , Potts Richard , Riedl Simon
Published: March 2020

In the EARS orographic forcing of rainfall, pronounced relief contrasts between shoulder areas and the axial rift sectors results in steep environmental and surface-process gradients, severed fluvial networks, and diverse vegetation types. Due to sustained Quaternary tectono-volcanic activity and the effects of a superposed, highly variable climate these basins have been further differentiated into distinct environments that are either isolated or fluvially connected on time scales of several 103 to 106 years. The EARS thus comprises important physical corridors, but also barriers with spatially varying topographic conditions and resource distribution. Varying paleo-environmental settings and the present-day distribution of some mammal groups in the EARS' Kenya Rift highlight the importance of rift corridors for the migration of species and the interchange of now geographically isolated lineages.

For example, the presently disjunct distribution of the Bat-eared fox (Otocyon megalotis), the Black-backed jackal (Canis mesomelas) and the Oryx sister taxa (Oryx beisa and O. gazella) in northeastern vs. southern Africa, or of various rainforest antelopes such as Bongo (Tragelaphus euryceros) in the Congo basin and beyond the EARS in central Kenya, suggests that variability in connectivity along and across the rift has influenced species dispersal. Protracted rifting dictates the overall geomorphic character of the migration corridors, but fluvial connectivity varies significantly as a response to orbitally driven climatic conditions. These factors were responsible for lateral change in vegetation cover, such as the distribution of wet forests that enabled dispersal in the equatorial sectors of the rift. Such conditions ultimately determined whether the meridionally oriented rift segments acted as gateways or barriers.
A scale invariance criterion for geophysical fluids
Authors: Schaefer-Rolffs Urs
Published: March 2020

Scale invariance of geophysical fluids is investigated in terms of a scale invariance criterion. It was developed by Schaefer-Rolffs et al. (2015) based on the implication that each scale invariant subrange shall have its own criterion. Two particular cases are considered, namely the synoptic scales with a significant Coriolis term and a case at smaller scales where the anelastic approximation is valid. The first case is characterized by a constant enstrophy cascade, while in the second case small-scale fluctuations of density, pressure, and temperature are taken into account. In both cases, the respective scale invariance criteria are applied to simple parameterizations of turbulent diffusion. It is demonstrated that only dynamic approaches are scale invariant.
MMS Observations of Short-Period Current Sheet Flapping
Authors: Richard Louis , Khotyaintsev Yuri , Graham Daniel , Russell Christopher , Le Contel Olivier
Published: March 2020

Flapping motions of current sheets are commonly observed in the magnetotail. Various wave modes can correspond to these oscillations such as kink-like flapping or steady flapping (e.g Wei2019). The period of such oscillating phenomena is usually longer than 100s and a typical observations consist only of a few crossings (e.g. Zhang2002). Here, we present a short period (T≈25s) flapping event observed by Magnetospheric Multiscale (MMS) mission at the dusk side plasmasheet on September 14, 2019. Using the multispacecraft observations, the direction of flapping as well as the direction of propagation of the current sheet are determined using the minimum variance, the timing method and the spatiotemporal derivative (Shi2005). It appears that the three methods give similar results with a direction of propagation of the current sheet which mainly lies in the ecliptic plane with a flapping velocity up to 500km/s. Based on the obtained wavelength and the variations of the direction of propagation we discuss which of the wave modes can explain the flapping.
Soil Education for General Public and School Students in Taiwan
Authors: Lai Hung-Yu , Tseng Wen-Yu , Yen Yu-Shan , Chen Kuei-San , Fong Chang-Jun
Published: March 2020

Soil is the foundation for plant growth, animal habitats, and human society; however, there are few people focus on the soil nowadays. Soil courses are limited in the current curriculum education of elementary and high schools in Taiwan. The soil exhibition tour was thus conducted and its main objective is to improve the understanding of soil resources and its importance on social human beings and environmental quality, especially for school students. The lessons about soil science and the new expression of art combined with the environment were prepared to convey. Graduate students firstly guided children to the school’s cropland on their campus and sampled soil by auger. Then they taught children how to describe the soil color via Munsell soil color charts, structure, consistence, and to determine textural class by feel method while going on a soil survey out of the classroom. Another topic, since the soil color was determined by developing processes and environmental conditions, it would be several kinds of hue. We collected soil samples from different counties in Taiwan. Teaching children doing the watercolor made of soil themselves and drawing the postcards, which shows the major soil characteristics, such as, textural triangle, six ecological functions, and soil profile on the cover following. The detail of the activities can be adjusted according to the population and the age of the participants; hence it’s suitable for general adults or students in the elementary and high schools.
Mapping of shallow subsurface water local variations at Mars’ moderate latitudes with FREND neutron telescope onboard ExoMars TGO
Authors: Malakhov Alexey , Mitrofanov Igor , Anikin Artem , Golovin Dmitry , Djachkova Maya , Lisov Denis , Litvak Maxim , Lukyanov Nikita , Nikiforov Sergey , Sanin Anton
Published: March 2020

Fine Resolution Epithermal Neutron Detector, FREND, is an instrument onboard ExoMars’ Trace Gas Orbiter (TGO). It uses neutron measurements to detect hydrogen (and thus water) variations in the shallow subsurface of the Martian soil. Similar experiments have been performed in the past on Mars, but FREND’s main characteristic is its neutron collimator that significantly narrows down the field of view (FOV) to 28° full cone which corresponds to a 60-200 km diameter spot on the surface. This is considerably smaller than the spatial resolution of previous experiments and thus allows us to peek inside local features of hydrogen variations.

The instrument has been measuring for almost one full Martian year currently so what we present is a result of continuous observations of shallow subsurface water between May 2018 and present. A technique to locate the most prominent local spots, either very “dry” or very “wet”, was developed to analyze the planetary surface from 70° North down to 70° South. It yielded several such local spots of interest that are presented, characterized and associated with particular geomorphological features or/and with the selected landing sites candidates.

It is known that water or water ice is not stable at the surface of Mars, especially closer to equator, thus locating areas with enhanced subsurface hydrogen or water is of much interest both scientifically and in terms of future exploration. FREND is most sensitive to water in the shallow subsurface of about 1 m deep, which makes such deposits easily accessible and valuable.
Constraining the process of intracontinental subduction: implications from petrology and Lu-Hf geochronology of eclogites from the Austroalpine Nappes
Authors: Miladinova Irena , Froitzheim Nikolaus , Nagel Thorsten , Janák Marian , Fonseca Raúl , Sprung Peter , Münker Carsten
Published: March 2020

The nucleation of subduction zone remains a widely discussed topic in the global tectonics. The prevalent view is that subduction starts within an oceanic plate. However, there is strong evidence that subduction can also be initiated within a continent. To test this hypothesis, we combine petrology, isotope geochronology and thermodynamic phase equilibrium modelling on eclogites from the Austroalpine Nappes of the Eastern Alps.

The high- and ultrahigh-pressure rocks occur in a ~400 km long belt from the Texel Complex in the west to the Sieggraben Unit in the east without remnants of Mesozoic oceanic crust. Garnet growth during pressure increase was dated using Lu-Hf chronometry. The results range between c. 100 and c. 90 Ma, indicating a short period of subduction. Combined with already published data, our estimates of metamorphic conditions indicate a field gradient with increasing pressure and temperature from northwest to southeast, where the rocks experienced ultrahigh-pressure metamorphism. The oldest Cretaceous eclogites (c. 100 Ma) are found in the Saualpe-Koralpe area which comprises widespread gabbros formed during Permian to Triassic rifting. This supports the hypothesis that subduction initiation was intracontinental and localized by a Permian rift. In the Texel Complex two-phased garnets yielded a Variscan-Eoalpine mixed age indicating re-subduction of Variscan eclogite-bearing continental crust during the Eoalpine orogeny. Jurassic blueschist-facies metamorphism at Meliata in the Western Carpathians and Cretaceous eclogite-facies metamorphism in the Austroalpine are separated by a time gap of ~50 Ma and therefore do not represent a transition from oceanic to continental subduction but rather separate events.
Targeted Glacial Geoengineering through Seabed Anchored Curtains
Authors: Wolovick Michael , Moore John , Jaiman Rajeev , Jelovica Jasmin , Keefer Bowie
Published: March 2020

Rapid sea level rise due to an ice sheet collapse has the potential to be extremely damaging to coastal communities and infrastructure, and conventional coastal protection techniques (dykes, levees, etc) can be quite expensive. In the past we have proposed that society might employ artificial sills and pinning points at critical marine ice streams in Antarctica to slow the rate of sea level rise at the source (Wolovick and Moore, 2018). However, thick earthen sills are likely to be extremely expensive and difficult to construct. If the goal of the intervention is only to block warm water from reaching the grounding line, then an alternate intervention consisting of thin flexible buoyant curtains anchored to the seabed might be employed instead. Flexible curtains are likely to be cheaper, more robust against iceberg collisions, and easier to remove in the event of unforeseen side effects. Here, we use a simple ice flow model to evaluate the effectiveness of such an intervention at three important Greenlandic outlet glaciers, and we make crude estimates of the forces on the curtain and of the likely cost of construction. We find that the single most important factor controlling the effectiveness of a thin water-blocking intervention (defined as either slowing glacier retreat or causing readvance) is the exposure of the glacier to deep warm water at the time of barrier construction. This means that, for Jakobshavn Isbrae, which has a deep (~1000 m) central trough extending well over 100 km inland, a water-blocking intervention is likely to be effective far into the future, and also that the preventable retreat (in comparison to a no-intervention scenario) is quite large. For Helheim and Kangerdlugssuaq, however, the central trough rises rapidly just a few tens of kilometers inland of the present-day calving front, removing the vulnerability to deep warm water after a relatively small retreat. This means both that the intervention must be begun relatively soon if it is to have an effect at those glaciers, and that the preventable retreat is smaller. With respect to the forces acting on the curtain, we find that the static tensile load on the curtain rises quadratically with the height above the seabed, and linearly with respect to the density contrast between the inner waters and the outer waters. Since the natural sills at the fjord mouths are roughly three times deeper at Helheim and Kangerdlugssuaq than they are at Jakobshavn, curtains at the former would need to be roughly an order of magnitude stronger than curtains at the latter. We estimate that this translates into roughly five times greater cost (per unit barrier length) at the two East Greenland glaciers than at Jakobshavn. Therefore, based on both cost and effectiveness, we find that this type of intervention is more favored for Jakobshavn than it is for Helheim and Kangerdlugssuuaq.
High Asia Refined Analysis Version 2 (HAR v2): a New Atmospheric Data Set for the Third Pole Region
Authors: Wang Xun , Tolksdorf Vanessa , Otto Marco , Scherer Dieter
Published: March 2020

Climatic-triggered natural hazards such as landslides and glacier lake outburst floods pose a threat to human lives in the third pole region. Availability of accurate climate data with high spatial and temporal resolution is crucial for better understanding climatic triggering mechanisms of these localized natural hazards. Within the framework of the project “Climatic and Tectonic Natural Hazard in Central Asia” (CaTeNA), High Asia Refined analysis version 2 (HAR v2) is under production, and is freely available upon request. HAR v2 is a regional atmospheric data set generated by dynamical downscaling of global ERA5 reanalysis data using the Weather Research and Forecasting (WRF) model. Compared to its predecessor (HAR), HAR v2 has an extended 10 km domain covering the Tibetan Plateau and the surrounding mountains, as well as a longer temporal coverage. It will be extended back to 1979, and will be continuously updated in the future. This presentation will contain the following aspects: (1) summarizing the WRF configuration; (2) validating HAR v2 against observational data; (3) comparing HAR v2 with other gridded data sets, such as the newly developed ERA5-Land reanalysis data; (4) providing information about data format, variable list, data access, etc.  
Experimental Study on the Hydraulic Desilting System of Dam Farm Pond
Authors: Hsu Yu-Chao , Wang Ji-Shang , Su Yu-Wen , Hung Tzu-Chieh , Jan Chyan-Deng , Fu Guei-Lin , Lin Jui-Jen , Fang Yen-Chun
Published: March 2020

Due to the effects of extreme climate, the frequency of drought has increased around the southern Taiwan in recent years. The development and utilization of water resources, especially in dry season, becomes more significant in the hillsides of southern Taiwan. Farm ponds are useful facilities for agriculture, especially in the hilly areas. In addition, farm ponds can provide the functions of water retention and detention, ground water recharge, land subsidence mitigation, water purification, ecological conservation and habitat environment. According to the results of fieldwork, about ten percentage of ponds are facing more serious sedimentation problems. Among these farm ponds, deposition in dam farm ponds may be more severe. Because the farm ponds are located on hilly areas where agriculture is active, the problem of sediment deposition is always issued. This study used an experiment model to study the feasibility of hydraulic desilting of dam farm pond. The experimental study was conducted in a tank of cube which has a volume of 1.0 m3, a stand pipe area of 0.01 m2, an inclined pipe area of 0.01 m2 and desilting pipe diameter of 0.03 m. The experimental arrangements included three positions of desilting pipes (setting0, setting1, setting3), two bottom orifice sizes (Do = 1.0 cm, 2.0 cm), three sediment deposition depths (EL = 30 cm, 40 cm, 50 cm) and three water levels (WL = 60 cm, 70 cm, 80 cm). Our study aims to figure out the most effective sediment removal ratio in the different arrangement of experiment. The inflow discharge varied from 450 to 4,000 cm3/s. The median diameter (d50) of the sediment used in experiments was 0.12 mm. According to the results of experiment, sediment removal ratio with bottom orifice of 2.0 cm is higher than bottom orifice of 1.0 cm under conditions of three different sediment deposition depths and three different water levels. The experimental results indicate that desilting pipes installed in the dam farm pond is helpful for removing sediment deposition. This study will also conduce to the promotion of conservation measures and water resources that related to farm ponds.
ARTEMIS: Advanced methodology development for Real-TimE Multi-constellation (BDS, Galileo and GPS) Ionosphere Services
Authors: Li Zishen , Wang Ningbo , Krankowski Andrzej , Huo Xingliang , Liu libo , Li Liang
Published: March 2020

In recent years the development of satellite navigation systems sped up and is no longer limited to well-known GPS and GLONASS systems. A good example of which are Europe’s Galileo and China’s BeiDou systems, which can be integrated for various scientific applications. ARTEMIS is a Chinese-Polish joint project concentrating on an important area of space research – space weather monitoring – through the development of new technologies and methods of Earth’s ionosphere monitoring. The main objective of the project is a development of the methodology for ionospheric real-time services using observations from BeiDou, Galileo and GPS systems, which are of extreme importance from professional (precise positioning, satellite navigation) and scientific points of view in the areas requiring current and accurate information on the state of the ionosphere.

 

The concept of ARTEMIS for real-time ionospheric space weather service is presented at first in this contribution, followed by the scientific progress from both Chinese and Polish sides during the year 2019. Benefiting from the real-time multi-constellation and multi-frequency GNSS data streams from regional and global permanent network stations, a prototype service system for real-time ionospheric monitoring was developed, which supports at current stage, the generation of global real-time Total Electron Content (TEC) maps, global Rate of TEC Index (ROTI) maps, as well as regional TEC/ROTI maps over Chinese and European regions. Using the home-made ionospheric scintillation (IS) monitoring receiver, i.e. BDSMART, an experimental campaign was carried out at low-latitude stations of China for the quality examination of BDSMART IS receivers. The ionospheric scintillation monitoring results from both GNSS L band and Low Frequency Array (LOFAR) low-frequency radio astronomical observations are highlighted by the Polish partner. The Chinese low-latitude Ionospheric Experimental Network (CHINE) for low-latitude ionospheric scintillation monitoring is now under construction. The generation of regional and global three-dimensional ionospheric electron densities in real-time is still in progress.
Disentangling the effects of micro-site ecology on Fennoscandian tree growth
Authors: Hartl Claudia , Düthorn Elisabeth , Tejedor Vargas Ernesto , Kirchhefer Andreas , Timonen Mauri , Holzkämper Steffen , Büntgen Ulf , Esper Jan
Published: March 2020

The long tradition in dendroclimatological studies across Fennoscandia is mainly due to the exceptional strong temperature sensitivity of tree growth, as well as the existence of well-preserved subfossil wood in shallow lakes and extent peat bogs. Although some of the world’s advanced multi-millennial-long ring width and density based climate reconstructions have been developed in northern Fennoscandia, it is still unclear if differences in micro-site ecology have been considered sufficiently in previous studies. In order to assess the effects of moist lakeshores versus drier inlands on forest productivity, we present a Fennoscandia-wide network of 44 Scots pine ring width chronologies from 22 locations between 59°-70°N and 16°-31°E. Clustering into coastal settings in northern Norway, continental sites in the lee of the Scands north of the polar circle, and locations south of the polar circle, our network reveals a general dependency of pine growth rates on latitude and July temperature. Differences between moist and dry sites are likely caused by associated effects on soil temperature. While trees at moist micro-sites at western locations exhibit higher growth rates, this pattern inverses under the more continental conditions of the east, where increased ring widths are found at drier sites. In addition to the latitudinal increase in growth sensitivity to July temperature, pines at moist sites tend to show a higher dependency to summer warmth. The highest temperature sensitivity and growth coherency is found in those regions where July temperatures range between 11.5 and 13.5°C and May precipitation totals fall below 100mm. This study not only emphasizes the effects of micro-site ecology on Fennoscandian tree growth, but also provides guidance for the selection of sampling sites for climate reconstructions.
South Africa’s agricultural dust sources and events from the MSG SEVIRI record
Authors: Eckardt Frank , Von Holdt Johanna , Kuhn Nickolaus , Palmer Anthony , Murray Jonathan
Published: March 2020

Our aim was to determine South Africa’s major dust sources using the MSG (Meteosat Second Generation) SEVIRI (Spinning Enhanced Visible and Infra-red Imager) image record from 2006-2016. A total of 334497 images were examined, which revealed 178 discrete dust plumes on 75 dust-producing days. These originated largely from the Free State to the north of Bloemfontein. Landsat derived National Geospatial data suggests that emission areas consist mostly of grass and low shrublands as well as commercial rainfed agriculture.

The dust emission season from June to January overlaps with the dry season and coincides with the maize harvest period. 2015 and 2016 saw almost half of all event days in the 11-year record, which is matched by a severe drought index (SPEI Standardised Precipitation-Evapotranspiration Index) and strong winds (ERA5). This period is also accompanied by a below average NDVI (Normalized Difference Vegetation Index) response for cropland areas, while DAFF (Department: Agriculture, Forestry and Fisheries) crop data reports a notable decline in Free State maize cover from 1.2 to 0.6 million hectares and a pronounced increase in fallow land from 140 thousand to 790 thousand hectares over the same time span.

Dust events adhere to distinct diurnal patterns, are almost entirely midday occurrences and are accompanied by hourly average windspeeds of up to 11 m s-1. HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) suggests that aerosols would largely head towards the Indian Ocean with the passing of cold fronts. South Africa’s major dust sources in the SEVIRI record appear to be mostly anthropogenic in nature and a function of both land cover and land management practices associated with rainfed agriculture on soils rich in silt and sand. The soil textures in the Free State, especially those associated with arenosols extend into the wider drier interior, including the Kalahari, where future climate scenarios have predicted increases in dust emissions from both soils and dunes. Notwithstanding other land-use practices, we would argue that the 2015-2016 dust season in South Africa provides an insight into potential future regional scenarios, given increases in drought, associated bare cover and an increase in windiness.
Observations of the Martian atmosphere by NOMAD on ExoMars Trace Gas Orbiter
Authors: Vandaele Ann Carine , Piccialli Arianna , Thomas Ian R. , Daerden Frank , Aoki Shohei , Depiesse Cédric , Erwin Justin , Neary Lori , Ristic Bojan , Robert Séverine , Trompet Loïc , Viscardy Sébastien , Willame Yannick , Gérard Jean-Claude , Liuzzi Giuliano , Villanueva Geronimo , Mason Jon , Patel Manish , Bellucci Giancarlo , Lopez-Moreno Jose-Juan ,   NOMAD Team
Published: March 2020

The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust probing the ultraviolet and infrared regions covering large parts of the 0.2-4.3 µm spectral range [1,2].

Since its arrival at Mars in April 2018, NOMAD performed solar occultation, nadir and limb observations dedicated to the determination of the composition and structure of the atmosphere. Here we report on the different discoveries highlighted by the instrument: investigation of the 2018 Global dust storm and its impact on the water uplifting and escape, its impact on temperature increases within the atmosphere as inferred by GCM modeling and observations, the dust and ice clouds distribution during the event, ozone measurements, dayglow observations and in general advances in the analysis of the spectra recorded by the three channels of NOMAD.

References

[1] Vandaele, A.C., et al., 2015. Planet. Space Sci. 119, 233-249.

[2] Vandaele et al., 2018. Space Sci. Rev., 214:80, doi.org/10.1007/s11214-11018-10517-11212.
Linking spatial heterogeneity of geomorphic properties, flow persistence and hydrological connectivity
Authors: Durighetto Nicola , Vingiani Filippo , Bertassello Leonardo Enrico , Camporese Matteo , Botter Gianluca
Published: March 2020

Headwater drainage networks have a key role in the transport of water and nutrients from the uplands to the sea. The presence of intermittent and ephemeral tributaries makes the river network highly dynamical, with expansion-contraction cycles that are observed in response to precipitation variability. Both the drainage density and the dynamics of the river network, however, are spatially heterogeneous, reflecting the patterns of geomorphic and physiographic features of the contributing catchment. One of the major effects of river network dynamics is that the hydrological connectivity between a hillslope site and the outlet changes through time, with shorter unchanneled lengths and faster drainage pathways when the network is expanded.

Using the empirical data gathered in a small alpine catchment in northern Italy, we present some analyses about the heterogeneity in the river network persistence and the catchment hydrological connectivity under different flow conditions encompassing dry and wet periods. Different areas of the catchment exhibit very different drainage densities, mirroring the spatial heterogeneity in the geomorphological properties of the catchment. In particular, the most ephemeral stretches of the network are associated with thinner soil layers, steeper slopes, and shallow bedrocks, while the most persistent tributaries emerge in regions characterized by thicker soil layers and moraine deposits. The frequency distribution of the unchanneled lengths is used as a tool to characterize the hydrological connectivity between hillslope sites and the river network. Our results show that network expansion affects the length of unchanneled pathways in a very heterogeneous way, with local variations associated to changing hydrological conditions ranging from 0 to one kilometer. Furthermore, we show that the drainage density is more heterogeneous during wet conditions, with an increase in the spatial variability of the unchanneled length of about 20%. These results hint at the importance of studying intermittent and ephemeral streams to enhance the understanding of the hydrology and biogeochemistry of headwater catchments.
Walker Circulation controls ENSO Atmospheric Feedbacks in Uncoupled and Coupled Climate Model Simulations
Authors: Bayr Tobias , Dommenget Dietmar , Latif Mojib
Published: March 2020

Many climate models strongly underestimate the two most important atmospheric feedbacks operating in El Niño/Southern Oscillation (ENSO), the positive (amplifying) zonal surface wind feedback and negative (damping) surface-heat flux feedback (hereafter ENSO atmospheric feedbacks, EAF), hampering realistic representation of ENSO dynamics in these models. Here we show that the atmospheric components of climate models participating in the 5th phase of the Coupled Model Intercomparison Project (CMIP5) when forced by observed sea surface temperatures (SST), already underestimate EAF on average by 23%, but less than their coupled counterparts (on average by 54%). There is a pronounced tendency of atmosphere models to simulate stronger EAF, when they exhibit a stronger mean deep convection and enhanced cloud cover over the western equatorial Pacific (WEP), indicative of a stronger rising branch of the Pacific Walker Circulation (PWC). Further, differences in the mean deep convection over the WEP between the coupled and uncoupled models explain a large part of the differences in EAF, with the deep convection in the coupled models strongly depending on the equatorial Pacific SST bias. Experiments with a single atmosphere model support the relation between the equatorial Pacific atmospheric mean state, the SST bias and the EAF. An implemented cold SST bias in the observed SST forcing weakens deep convection and reduces cloud cover in the rising branch of the PWC, causing weaker EAF. A warm SST bias has the opposite effect. Our results elucidate how biases in the mean state of the PWC and equatorial SST hamper a realistic simulation of the EAF.
HydroGFD3: a climatological and real-time updated hydrological forcing dataset
Authors: Berg Peter , Almén Fredrik , Bozhinova Denica , Mook Riejanne
Published: March 2020

Hydrological forecasting benefits substantially from good initial conditions, which translate information into the forecast. It is therefore important to perform frequent updates of the initial state of the model before the forecast, which demands good meteorological forcing data. For a continental or global hydrological model, it is difficult to find observational data sets which fulfill the requirements of (i) long time series for calibration and spin up, (ii) consistent quality, (iii) at least daily time steps, and (iv) at least data for temperature and precipitation. HydroGFD3 is a new data set that fulfills all the criteria and provides real-time updated data.

HydroGFD3 builds upon the ERA5 reanalysis data set, and performs a bias correction for each new produced month. In contrast to earlier versions (Berg et al., 2018), HydroGFD3 is based on a multi-source climatological background, upon which individual days are produced by adding anomalies from different freely available monthly global observational data sets. These are then disaggregated based on the ERA5 reanalysis. For production redundancy and local tailoring, HydroGFD3 is produced in several tiers, each using different observational data sets originating from GPCC and CPC. Further, intermediate daily updates of the reanalysis through the source ERA5T allow the data set to be updated to within a few days of real-time.

To reach actual real-time, one tier is based on a bias correction method calibrated on the period 1980-2009, which is applied on ERA5T, and further prolonged to current day using the ECMWF deterministic forecasts. The assumption for this to work is that the forecasts have a similar bias as the reanalysis model, which is currently the case. The method also allows bias correction of the forecasts themselves; solving the issue of “drift” in the forecasts as the hydrological model adjusts to the (biased) climatological state of the forcing data.

Berg, Peter, Chantal Donnelly, and David Gustafsson. "Near-real-time adjusted reanalysis forcing data for hydrology." Hydrology and Earth System Sciences 22.2 (2018): 989-1000.

 