bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating model-simulated and satellite-derived SM using in situ observations under different environment conditions in China
Authors: Wang Yuanyuan , Li Guicai
Published: March 2020

Soil moisture (SM) is a key variable in understanding the climate system through its controls on the land surface energy and water budget. Large scale SM products have become increasingly available thanks to development in microwave remote sensing and land surface modeling. Comprehensive assessments on the reliability of satellite-derived and model-simulated SM products are essential for their improvement and application. In this research, the active, passive and combined Climate Change Initiative (CCI V04.2) SM products and the China Land Data Assimilation System (CLDAS V2.0) SM products were evaluated by comparing with in situ observed data over three networks in China: Hebi, Naqu and Heihe. The three sites have different environmental conditions and sensor densities, providing observations covering more than 2 years. Four statistic scores were calculated: R (considering both original data and anomalies), Bias, RMSE, ubRMSE. TC (Triple Collocation) analysis was also carried out in which uncertainties in observations are taken into account. Results indicate that the performance of the two SM products varies between the monitoring networks. For Naqu site, both products show good performance, with CCI-SM showing slightly higher R and lower ubRMSE. For Hebi site, CLDAS-SM performs better than CCI-SM, whereas for Heihe site, CLDAS-SM performs worse than CCI-SM. The expected uncertainty (0.04 m3/m3) can be achieved in Naqu and Heihe site by CCI-SM, and in Hebi and Naqu site by CLDAS-SM, which is quite encouraging. The two products agree in terms of sign of the Bias value, which is positive in Hebi and negative in Naqu and Heihe. Among all the three networks, Heihe site exhibits the lowest accuracy due to its complicated terrain and heterogeneous land surface. Ranom of CLDAS-SM in Heihe is close to 0, indicating its inability to capture short term variability. TC results reveal that for Naqu site the observation data have quite good qualities, while for Hebi site CLDAS-SM is more approximate to ‘ground truth’ than in situ observations, suggesting a refinement of network maybe needed in the future. Overall, the two products are complementary. CLDAS-SM performs better in populated area (e.g., Hebi) where meteorological forcing is more accurate and CCI-SM performs better in remote areas (Naqu, Heihe) where RFI is usually low. More reliable validation networks are needed in the future to comprehensively understand the advantages and disadvantage of the two SM products in China.
Fault System Evolution and Its Influences on Buried-hills Formation in Tanhai Area of Jiyang Depression, Bohai Bay Basin, China
Authors: Zhang Meng , Wu Zhiping , Yan Shiyong
Published: March 2020

Buried-hills, paleotopographic highs covered by younger sediments, become the focused area of exploration in China in pace with the reduction of hydrocarbon resources in the shallow strata. A number of buried-hill fields have been discovered in Tanhai area located in the northeast of Jiyang Depression within Bohai Bay Basin, which provides an excellent case study for better understanding the structural evolution and formation mechanism of buried-hills. High-quality 3-D seismic data calibrated by well data makes it possible to research deeply buried erosional remnants. In this study, 3-D visualization of key interfaces, seismic cross-sections, fault polygons maps and thickness isopach maps are shown to manifest structural characteristics of buried-hills. Balanced cross-sections and fault growth rates are exhibited to demonstrate the forming process of buried-hills. The initiation and development of buried-hills are under the control of fault system. According to strike variance, main faults are grouped into NW-, NNE- and near E-trending faults. NW-trending main faults directly dominate the whole mountain range, while NNE- and near E-trending main faults have an effect on dissecting mountain range and controlling the single hill. In addition, secondary faults with different nature complicate internal structure of buried-hills. During Late Triassic, NW-trending thrust faults formed in response to regional compressional stress field, preliminarily building the fundamental NW-trending structural framework. Until Late Jurassic-Early Cretaceous, rolling-back subduction of Pacific Plate and sinistral movement of Tan-Lu Fault Zone (TLFZ) integrally converted NW-trending thrust faults into normal faults. The footwall of NW-trending faults quickly rose and became a large-scale NW-trending mountain range. The intense movement of TLFZ simultaneously induced a series of secondary NNE-trending strike-slip faults, among which large-scale ones divided the mountain range into northern, middle and southern section. After entry into Cenozoic, especially Middle Eocene, the change of subduction direction of Pacific Plate induced the transition of regional stress field. Near E-trending basin-controlling faults developed and dissected previous tectonic framework. The middle section of mountain range was further separated into three different single hill. Subsequently, the mountain range was gradually submerged and buried by overlying sediments, due to regional thermal subsidence. Through multiphase structural evolution, the present-day geometry of buried-hills is eventually taken shape.
Selective acceleration of O+ by drift-bounce resonance in the Earth’s magnetosphere: MMS observations
Authors: Oimatsu Satoshi , Nosé Masahito , Le Guan , Fuselier Stephan A , Ergun Robert E , Lindqvist Per-Arne , Sormakov Dmitry
Published: March 2020

We studied O+drift-bounce resonance using Magnetospheric Multiscale (MMS) data. A case study of an event on 17 February 2016 shows that O+ flux oscillations at ~10–30 keV occurred at MLT ~ 5 hr and L~ 8–9 during a storm recovery phase. These flux oscillations were accompanied by a toroidal Pc5 wave and a high-speed solar wind (~550 km/s). The azimuthal wave number (m-number) of this Pc5 wave was found to be approximately –2. The O+/H+ flux ratio was enhanced at ~10–30 keV corresponding to the O+ flux oscillations without any clear variations of H+ fluxes, indicating the selective acceleration of O+ ions by the drift-bounce resonance. A search for the similar events in the time period from September 2015 to March 2017 yielded 12 events. These events were mainly observed in the dawn to the afternoon region at L~ 7–12 when the solar wind speed is high, and all of them were simultaneously identified on the ground, indicating low m-number. Correlation analysis revealed that the O+/H+ energy density ratio has the highest correlation coefficient with peak power of the electric field in the azimuthal component (Ea). This statistical result supports the selective acceleration of O+ due to the N = 2 drift-bounce resonance.
Sea-level rise impacts on the tides of the European Shelf: mechanisms analysis
Authors: Idier Deborah , Paris François , Le Cozannet Goneri , Boulahya Faiza , Dumas Franck
Published: March 2020

Sea-level rise (SLR) can modify not only total water levels, but also tidal dynamics. Several studies have investigated the effects of SLR on the tides of the western European continental shelf (mainly the M2 component). Idier et al. (2017) further investigate this issue using a modelling-based approach, considering uniform SLR scenarios from −0.25 m to +10 m above present-day sea level. Assuming that coastal defences are constructed along present-day shorelines, the patterns of change in high tide levels (annual maximum water level) are spatially similar, regardless of the magnitude of sea-level rise (i.e., the sign of the change remains the same, regardless of the SLR scenario) over most of the area (70%). These changes are generally proportional to SLR, as long as SLR remains smaller than 2 m. Depending on the location, they can account for +/−15% of regional SLR. Changes in high tide levels are much less proportional to SLR when flooding is allowed, in particular in the German Bight. However, some areas (e.g., the English Channel) are not very sensitive to this option, meaning that the effects of SLR would be predictable in these areas, even if future coastal defence strategies are ignored.

In the present work, we focus on the mechanisms driving these tide changes, especially the bed friction damping, the resonance properties and the reflection at the coast, i.e., local and non-local processes. Additional simulations are done to quantify the effect of these mechanisms on tide changes.

 

Reference: Idier D., Paris F., Le Cozannet G., Boulahya F., Dumas F. (2017) Sea-level rise impacts on the tides of the European Shelf. Continental Shelf Research, 137, 56-71.
Water-use efficiency of crops under drought: A global meta-analysis
Authors: Yu Liuyang , Zhao Xining , Gao Xiaodong
Published: March 2020

Crops are facing greater drought stress and are being relocated to more arid regions as the climate changes. Ranking high-yield crops according to their efficient and sustainable use of water resources under drought stress is critical for selecting suitable crops to relieve the stress on food security and water resources in dryland agricultural regions. A global meta-analysis was conducted by incorporating 907 experimental observations from 96 research studies to assess the water-use efficiency (WUE) of 40 crop species under drought stress conditions across various environments. The results showed that compared with well-watered conditions, drought stress decreased crop WUE significantly by an average of 2.8%, but the effects varied among crop species. Most (93.6%) of the variance in crop WUE could be explained by four factors and drought intensity was the most important factor (32.9%), followed by climate type (23.5%), soil texture (20.2%), and crop type (17.1%). Perennial, liana, fiber, and fruit crops displayed the largest increases in WUE under drought stress. Moreover, crops grown in semi-arid regions with medium-textured soil and a drought intensity of < 20% showed the best WUE performance relative to crops grown in other environments. The specific ranks of crops according to their WUE in response to drought across different environments were given. This study highlights factors affecting the WUE of crops in response to drought and provides high-yield crop candidates that can adapt to drought in drylands. The dataset has been made freely available and could be updated with more crop species in the future.
Temporal-Spatial Assessment of Water and Soil Conversation Value of Gannan forest in China
Authors: Fu Chun , Yang Li , Wu Yuanzhuo
Published: March 2020

Gannan forest is an important safety barrier in southeast China. In recent years, Ecological engineering such as Natural Forest Protection, Close Hillsides for Forestry and so on have been implemented in this area. But its ecosystem service value is in a decrease. Especially the soil erosion is serious. The analysis on the dynamic trend of water and soil conservation ecosystem service value and its formation mechanism is of big practical and theoretical significance. In our study, land use change is considered as entry point, while land use remote sensing data and spatial statistic data are used as our database. Logistic-CA-Markov complex model is constructed to predict the space-time evolution trend of forest land use under different circumstance. Based on the prediction, water and soil conservation ecosystem service value is evaluated using assessment approaches like shadow project approach and production cost method. Strategies to promote the ecosystem service are then put forward.
Lattice preferred orientation of graphite in a graphite ore as investigated by the anisotropy of out-of-phase magnetic susceptibility
Authors: Hrouda Frantisek , Chadima Martin , Ježek Josef , Mrázová Štěpánka , Poňavič Michal
Published: March 2020

Literature data on single crystals of graphite shows that this mineral is diamagnetic and strongly anisotropic. In addition, it possesses high electrical conductivity and extremely strong conductivity anisotropy. The AC magnetic susceptibility of graphite exhibits weak and negative in-phase component and relatively strong out-of-phase component, which is no doubt due to electrical eddy currents. Consequently, if the graphite crystals are oriented preferentially by crystal lattice (LPO) in graphite ore, one would expect strong anisotropy of magnetic susceptibility (AMS) of the ore. Unfortunately, the standard AMS, which is in fact the anisotropy of the in-phase component of susceptibility (ipAMS), reflects not only the LPO of graphite, but also the preferred orientation of paramagnetic and ferromagnetic admixtures. On the other hand, the anisotropy of out-of-phase susceptibility (opAMS) indicates LPO of graphite, free of the effects of non-conductive paramagnetic and ferromagnetic minerals.

The above theoretical expectations were tested on natural South Bohemian graphite ores occurring in the wide vicinity of the town of Český Krumlov in the Moldanubian Unit and being mined for pencil industry in the past. The ores are metamorphic in origin and one can therefore expect strong LPO of graphite in them. The graphite ores were sampled in two localities near the town of Český Krumlov, one being a road cut outcrop and the other one being a graphite mine. In both cases, the in-phase susceptibility is very low, in the order of 10-6 [in SI units], being positive in some specimens and negative in the others. This indicates simultaneous and more or less balanced control by graphite and paramagnetic and/or ferromagnetic minerals. On the other hand, the out-of-phase susceptibility is much higher, in the order of 10-4, and no doubt indicates its graphite control. The degree of opAMS is truly high, P = 2 to 3, and the opAMS foliation is closely related to the metamorphic foliation in ores and wall rocks. All this indicates a conspicuous LPO of graphite in the ore that was probably created during Variscan regional metamorphism and associated ductile deformation.
The Impact of the Extreme 2015-16 El Niño on the Mass Balance of the Antarctic Ice Sheet
Authors: Bingham Rory , Bodart Julien
Published: March 2020

Interannual variations associated with El Niño-Southern Oscillation can alter the surface-pressure distribution and moisture transport over Antarctica, potentially affecting the contribution of the Antarctic ice sheet to sea level. Here, we combine satellite gravimetry with auxiliary atmospheric datasets to investigate interannual ice-mass changes during the extreme 2015-16 El Niño. Enhanced precipitation during this event contributed positively to the mass of the Antarctic Peninsula and West Antarctic ice sheets, with the mass gain on the peninsula being unprecedented within GRACE’s observational record. Over the coastal basins of East Antarctica, the precipitation-driven mass loss observed in recent years was arrested, with pronounced accumulation over Terre Adélie dominating this response. Little change was observed over Central Antarctica where, after a brief pause, enhanced mass-loss due to weakened precipitation continued. Overall, precipitation changes over this period were sufficient to temporarily offset Antarctica’s usual (approximately 0.4 mm yr-1) contribution to global mean sea level rise.
A global bibliometric perspective on soil erosion modelling
Authors: Bezak Nejc ,   Soil Erosion Modelling Team
Published: March 2020

Systematic bibliometric investigations are useful to evaluate and compare the scientific impact of journal papers, book chapters and conference proceedings. Such studies allow the detection of emerging research topics, the analyses of cooperation networks, and the collection of in-depth insights into a specific research topic. In the presented work, we carried out a bibliometric study in order to obtain an in-depth knowledge on soil erosion modelling applications worldwide.

As a starting point, we used the soil erosion modelling meta-analysis data collection generated by the authors of this abstract in a joint community effort. This database contains meta-information of more than 3,000 documents published between 1994 and 2018 that are indexed in the SCOPUS database. The documents were reviewed and database entries verified. The database contains various types of meta-information about the modelling studies (e.g., model used, study area, input data, calibration, etc.). The bibliometric information was also included in the database (e.g., number of citations, type of publication, Scopus category, etc.). We investigated differences among publication types and differences between papers published in journals that are part of various Scopus categories. Moreover, relationships between publication CiteScore, number of authors, and number of citations were analyzed. A boosted regression tree model was used to detect the relative impact of the selected meta-information such as erosion model used, spatial modelling scale, study period, field activity on the total number of citations. Detailed investigation of the most cited papers was also conducted. The VOSviewer software was used to analyze citations, co-citations, bibliographic coupling, and co-authorship networks of the database entries.  

Our bibliometric investigations demonstrated that journal publications, on average, receive more citations than book series or conference proceedings. There were differences among the erosion models used, and some specific models such as the WaTEM/SEDEM model, on average, receive more citations than other models (e.g., USLE). It should also be noted that self-citation rates in case of most frequently used models were similar. Global studies, on average, receive more citations than studies dealing with plot, regional, or national scales. According to the boosted regression tree model, model calibration, validation, or field activity do not have significant impact on the obtained publication citations. Co-citation investigation revealed some interesting patterns. Our results also indicate that papers about soil erosion modeling also attract citations from different fields and better international cooperation is needed to advance this field of research with regard to its visibility and impact on human societies.    
Empirical Site Amplification Modelling for Horizontal and Vertical Ground Motions in Taiwan
Authors: Kuo Chun-Hsiang , Chao Shu-Hsien , Lin Che-Min , Huang Jyun-Yan , Wen Kuo-Liang
Published: March 2020

Site amplification behavior are important in ground motion prediction. Seismic waves were amplified and caused significant building damages in the Taipei Basin by the 1986 Hualien offshore (subduction interface) and the 1999 Chi-Chi earthquakes (crustal), for which both of the epicentral distances were nearly 100 km. To understand local site amplifications in Taiwan, empirical site amplification factors for both horizontal and vertical ground motions are studied using recently constructed strong motion and site databases for the free-field TSMIP stations. Records of large magnitude earthquakes of MW larger than 5.5 from 1991 to 2016 were selected for this study. Site amplification factors at site conditions with Vs30 between 120 m/s to 1600 m/s and bedrock accelerations up to 0.8 g were evaluated using ratios of spectral accelerations at different periods. The reference site condition, i.e. the engineering bedrock, is assumed as Vs30 of 760 m/s (B/C boundary) in this study. Our empirical site amplification form are borrowed from the site response function of ASK14 and CY14 ground motion models in NGA-West2 project with slight modification. Therefore our site amplification model includes a linear amplification term and a nonlinear deamplification term. The coefficients of the empirical models were obtained by a nonlinear regression analysis using the selected Taiwan data. Site amplification factor is a function of Vs30 and spectral intensity in the model. Similar linear site amplification factor to the NGA models is derived in our model; however, more significant soil nonlinearity behavior than the NGA models is likely captured from the empirical data. The amplification factor in vertical component is smaller than that in horizontal.
Influence of Natural Organic Matter on the Fate of Cadmium During Microbial Ferrihydrite Reduction
Authors: Zhou Zhe , Muehe E. Marie , Tomaszewski Elizabeth J. , Kappler Andreas , Byrne James M.
Published: March 2020

Ferrihydrite (Fh) is a short-range ordered Fe(III) oxyhydroxide which is often associated with significant amounts of trace metals in soils and sediments. Fh is frequently observed to be unstable under reducing conditions and can be transformed into secondary Fe minerals, during which associated trace metals are either redistributed in the minerals or released into solution. Natural organic matter (NOM), often coexisting with Fe minerals, is known to alter the transformation pathways of Fh, however, its effect on associated trace metals is not well known. Here we investigated how cadmium (Cd) is redistributed when Fh undergoes microbial Fe(III) reduction in the presence of NOM. Incubation with the Fe(III)-reducing bacteria Geobacter sulfurreducens showed that the rate and extent of reduction of Cd-loaded Fh were enhanced by increasing concentrations of NOM (i.e. increasing C/Fe ratio). Under low C/Fe ratios, only 3-5% of Fe(III) was reduced, but around 70% of pre-adsorbed Cd was released into the aqueous phase due to Fh transformation to lepidocrocite. At high C/Fe ratio (1.6), the Fe(III) reduction rate in the first 6 hours became nearly 3 times faster than in the absence of NOM, and more than 35% of Fe(III) was reduced over 5 days, possibly because the adsorbed NOM decreased the size of aggregates and the residual NOM in solution worked as electron shuttle. No Fh transformation was observed (using Mössbauer spectroscopy or X-ray diffraction) suggesting NOM could impede Fh crystal growth, and there was only negligible Cd release into solution. Lower concentrations of aqueous Cd lowered the metal's toxicity toward Geobacter sulfurreducens thus enabling more prolonged microbial reduction. The negligible Cd released during microbial Fh reduction might be due to recapture of Cd (initially bound to Fh) by NOM adsorbed on Fh. In summary, our study suggests the presence of NOM can be beneficial for the stability of Cd adsorbed to Fh under reducing conditions.
Identifying sources of changed precipitation in paleoclimate studies through moisture tracking: A case study for orbital extremes over the Mediterranean Sea
Authors: van der Ent Ruud , Bosmans Joyce , Haarsma Rein , Drijfhout Sybren , Hilgen Frits
Published: March 2020

Enhanced winter precipitation over the Mediterranean Sea at times of minimum precession and maximum obliquity could provide freshwater required to form orbitally-paced sedimentary cycles across the Mediterranean Sea floor, offering an alternative to monsoonal runoff. We investigate the sources of the enhanced winter precipitation by applying a moisture tracking model (WAM-2layers) on the results of idealized orbital extreme experiments with a state-of-the-art climate model (EC-Earth).

Tracking the moisture sources of the enhanced winter precipitation over the Mediterranean Sea shows that the source differs during the winter half year. In fall, the majority of the precession-induced precipitation increase originates from the Mediterranean itself. However, in late winter, the increase can be attributed to enhanced moisture advection from the Atlantic. This agrees with changes in evaporation and air-sea temperature differences over the Mediterranean. The obliquity-induced precipitation increase shows much less differences, with an equal contribution of local and Atlantic sources.

The mechanism behind the Atlantic source of moisture is not related to storm track activity, but to a weakened Azores High and slightly higher surface pressure over North Africa. The resulting anomalous circulation patterns generate enhanced Atlantic moisture transport towards the Mediterranean. Our combined climate and moisture tracking modelling approach thus provides an alternative mechanism for Atlantic sources of orbitally-paced Mediterranean precipitation changes.

The results of this study have been published in:

Bosmans, J. H. C., van der Ent, R. J., Haarsma, R. J., Drijfhout, S. S. and Hilgen, F. J.: Identifying sources of changed precipitation in paleoclimate studies through moisture tracking: A case study for orbital extremes over the Mediterranean Sea, Paleoceanogr. Paleoclimatology, accepted, doi:10.1029/2019PA003655, 2020.

The atmospheric moisture tracking through WAM-2layers revealed concrete information about the evaporative sources of enhanced/reduced precipitation. This method has not been previously applied in paleoclimate studies, but thus proved to be a powerful tool in attributing reasons for precipitation changes in addition to climate model experiments and classical meteorological analyses. New ideas for collaborations to apply this method in other (paleo)climate studies are welcome.
Similarities and differences of microseism and microbarom source regions reconstructed from the seismo-acoustic Kazakhstani network
Authors: Smirnov Alexandr , Le Pichon Alexis
Published: March 2020

The monitoring network of the Kazakhstani Institute of Geophysical Researches includes seismic and infrasound arrays. The PMCC method helps identifying microseisms in seismic records and microbaroms in infrasound records effectively. Simulation of the microbarom strength, propagation path and signal attenuation are well developed for the moment, and for microseisms as well. However, the bathymetry effect on the source intensity shall be taken into account to model microseisms.

Results of the source parameter simulations and microbaroms and microseisms detections are compared at 7 Kazakhstani seismic and infrasound arrays. These comparisons are also carried out between collocated seismic and infrasound arrays. Similarities and differences between the reconstructed source regions of microseisms and microbaroms are discussed. Beside this study, the advantages of integrating the infrasound and seismic methods have been shown for studying seismoacoustic signals from severe storms.
Recent ecological trajectory of lake Taihu and land-use history reconstructed from lake sediment DNA
Authors: Giguet-Covex Charline , Lin Qi , Gielly Ludovic , Arnaud Fabien , Zhang Ke
Published: March 2020

More than 80% of shallow lake ecosystems in the Yangtze floodplain suffer significant disturbances from the 50’s, especially eutrophication. These environmental degradations and subsequent loss of services are related with the important and rapid development of the agriculture, industry, urban areas and the population boom in the region. Lake Taihu is one of the largest lakes of the floodplain and represents an important water resource (for drinking and fishing) for the population of the two big cities on the lake shore. This lake experimented two shifts toward the degradation of the trophic state: one in the 50-60’s and a second in 80’s.

In order to document the causes of these ecological shifts, we applied the DNA metabarcoding approach on lake sediments and focused on plants as proxy of land use. Whereas this proxy has been successfully applied in many lakes over the world, it has never been tested in large shallow lakes and not in China either.

We show important changes in land use in 50’s and 80’s related with agricultural developments (i.e. intensification) and urban expansion, respectively. In fact, in the 50’s crop plants are increasing (rapeseed and/or cabbage, rice and/or wheat, barley and Poaceae) whereas in 80’s, we record the development of several plants associated to gardens (e.g. ornamental species). Moreover, this last period is characterised by the presence of trees mostly cultivated along stream banks to protect dikes against erosion. Between the 80’s and the years 2000, the plant diversity recorded in the sediment strongly increase, which may be due to higher detrital inputs (i.e. more efficient DNA transfer). The timing in land-use changes corresponds to the main shifts in lake trophic state.
Structural noise analysis in the simulation of hydrological models using a synthetically defined output variable
Authors: Vidmar Andrej , Brilly Mitja
Published: March 2020

The calibration of the parameters of the conceptual model based on the Gauss-Marquardt-Levenberg (GLM) procedure in combination with singular value decomposition and Andrey Tikhonov regularization allows the calculation of the exact parameter values by synthetically determined flows. With this procedure, the calibration noise is practically eliminated in simulating phenomena based on the measured values of the output variable. The noise in the calculation results is practically the same when calibrating and validating the results. The residual noise in the results is due to the noise of the concept of the model, the design of the model, and the accuracy of the measurements themselves.

An analysis based on synthetically determined discharges is selected for the study. Instead of measurements, we calibrated the model by calculated discharges with known parameters and performed the calibration procedure. Thus, we eliminated measurement noise, model conception noise, and model design noise from the results. From a mathematical standpoint, perfect calibration can be expected in the calibration process, or the deviations are due to the noise contained in a particular calibration procedure. The differences between the calculation and the synthetic result contain only the noise of the calibration process.

For the hydrological model, we have chosen a version of the HBV program called HBV-light. The model is partially distributed since it allows the basin to be divided into smaller sub-basin units. Each sub-basin can be further subdivided into smaller areas based on land use and altitude. The model includes the following computational procedures that describe hydrological processes: snow accumulation and melting, evapotranspiration assessment and soil moisture calculation, subsoil runoff, and water flow transformation in a riverbed (Bergström, 1995; IHMS, 1999).

The calculations were performed on the HBV-Light software on the test model, Dreta river model, and the Savinja river basin model, a tributary of the Sava River in Slovenia. The test model has 16 parameters, and we have achieved full calibration accuracy with the GLM calibration process. The Dreta River model on the head part of the Savinja River Basin contains 34 parameters. The results of the calculations revealed weaknesses in the concept of the model. The Savinja River Basin subdivided into 77 sub-basins and results of the calculations showed the benefits of using regularization when calibrating the model.
Analyzing the atmospheric scales involved in sea-breeze formation and frontal characteristics
Authors: Arrillaga Jon Ander , Jiménez Pedro , Vilà-Guerau de Arellano Jordi , Jiménez Maria Antonia , Román-Cascón Carlos , Sastre Mariano , Yagüe Carlos
Published: March 2020

We investigate sea-breeze (SB) frontal passages troughout a 10-year period. Spanning the whole period, numerical simulations from the Weather Research and Forecasting (WRF) model are compared with a comprehensive observational database from the Cabauw Experimental Site (Ruisdael Project). On the one hand, a fine horizontal resolution of 2 km is employed in the numerical simulations, and the observational vertical levels within the first 200 m above the surface are replicated. On the other hand, an algorithm based on objective and strict filters is applied to both observations and simulations to select the SB events. This methodology allows to investigate the atmospheric scales influencing the SB formation and their interaction with local turbulence in a robust and objective way.

By carrying out a filter-by-filter comparison, we find that the simulated large-scale conditions show a good rate of coincidence with the observations (69%). Small biases in the large scale wind direction, however, induce important deviations in the surface-wind evolution. Regarding the mesoscale forcings, the land-sea temperature gradient is overestimated in average up to 4 K, producing stronger SB fronts in WRF. The analysis of the SB frontal characteristics and impacts is carried out by classifying the events into three boundary-layer regimes (convective, transition and stable) based on the value of the sensible-heat flux at the moment of the SB onset. The stronger SB in the model leads to enhanced turbulence particularly in the convective and transition regimes: the friction velocity, for instance, is overstated by around 50% at the SB onset. In addition, the arrival of the SB front enhances the stable stratification and gives rise to faster afternoon and evening transitions compared with situations solely driven by local atmospheric turbulence.

The obtained results can be considered a benchmark of the aspects to be improved in order to produce finer SB forecasts and more adequate representations of the associated physical processes, particularly during the afternoon and evening transition of the ABL.
Do oscillating redox conditions affect long-term Si release from phytoliths?
Authors: Koebernick Nicolai , Kaiser Klaus , Klotzbücher Anika , Mikutta Robert , Vetterlein Doris , Klotzbücher Thimo
Published: March 2020

Phytoliths are a major source of plant-available Si in weathered soils, particularly for crops with high Si demand, such as rice. Yet, not much is known about the evolution of Si release from phytoliths under real soil conditions. The extraction of phytoliths from soil is difficult and usually leads to changes in phytolith surface chemistry. Paddy rice cultivation induces oscillations in redox potential by alternating submergence and drainage. These oscillations may have a major impact on the evolution of phytolith Si release. For instance, reduced Fe2+, abundantly in solution under low redox potential may sorb onto negatively charged phytolith surfaces and form iron oxide coatings when redox potential rises after drainage. We thus hypothesise that phytolith Si release decreases with time in soil as phytolith surfaces are increasingly coated with oxides and organic matter. To test the effect of oscillating redox potential on phytolith surface chemistry and implicit changes in Si release we conduct experiments with phytoliths extracted from rice straw by dry ashing. Extracted phytoliths are sequentially exposed to soil solutions with contrasting redox potentials (anoxic vs. oxic), using either alternating anoxic-oxic solutions or exclusively oxic solutions. Anoxic exposure is conducted in Ar atmosphere (< 1% O2 partial pressure). After each exposure events the filtrate is analysed for pH and redox potential, Fe2+ with the Ferrozine method, and total Fe, Al and Si with inductive-coupled plasma-optical emission spectrometry. Filter residues are sampled and analysed after 1, 2, 4, and 8 exposure steps (each lasting 2 hours), respectively. Surface chemical composition is analysed with X-ray photoelectron spectroscopy. Specific surface area is determined with N2 gas adsorption at 77 K and surface charge is measured by determining electrophoretic mobility using dynamic light scattering. Batch dissolution experiments in mini-reactors are carried out for assessing the Si release of untreated and treated phytoliths. The experimental results will provide important information on the changes of phytolith surface chemistry and Si release from phytoliths in systems with alternating redox potentials such as rice paddies.
Integrating Climate and Socioeconomic Pathways to Calculate the Future Cost of Catastrophes
Authors: Clarke Alastair , Koch Alexander , Robinson Eric , Cipullo Michelle , Latchman Shane , Sousounis Peter
Published: March 2020

The cost of future catastrophes will depend on changes to the hazard, exposure and vulnerability. Previous work has shown how climate change could affect the financial losses from damaged buildings by altering the frequency, severity and other characteristics of the hazard, but has not shown how socioeconomic trends could affect losses by altering the total number, spatial distribution and vulnerability of buildings.

We extend and apply urban scaling theory to model the spatiotemporal evolution of exposure using population projections that are consistent with Shared Socioeconomic Pathways (SSPs). The exposure sets are integrated with hazard catalogues that are consistent with Representative Concentration Pathways to give five views of UK windstorm risk for the year 2100.

SSPs describe five plausible futures where socioeconomic trends have made mitigation of, or adaptation to, climate change harder or easier. For example, one SSP describes a global panacea of co-operative, sustainable development while another describes a fragmented, under-developed world heavily-reliant on fossil fuels. AIR’s present-day exposure set, representative of all insurable properties in the UK, is perturbed by the SSPs to create an ensemble of plausible exposure sets for the year 2100. This ensemble is run through the AIR Extratropical Cyclone model for Europe with four stochastic event-based catalogues that represent the present hazard and three plausible future hazards posed by 1.5°C, 3°C and 4.5°C increases in global temperature.

Previous work found that global warming of 1.5°C to 4.5°C would increase the Average Annual Loss (AAL) from UK windstorms by 11% to 25%. We find that changes in exposure alone, dictated by the SSPs, lead to a wider range of changes in AAL. Urbanisation occurs under all SSPs resulting in exposure concentrating in cities and regional-level variation in AAL. Changes in AAL will further widen when integrated with the future hazard catalogues.

The results can help governments and public bodies to decide on a strategy for future urban and rural development, and how much to invest in protective measures against catastrophes. The framework can be extended to other perils in other countries adapting to climate change.
Energy and momentum flux around comet 67P throughout the Rosetta mission
Authors: Nilsson Hans , Williamson Hayley , Stenberg Wieser Gabriella , Richter Ingo , Götz Charlotte
Published: March 2020

We calculate the momentum and energy flux of ions measured by the Ion Composition Analyzer (ICA) on the Rosetta mission at comet 67P/Churyumov-Gerasimenko. We find that the total ion energy and momentum flux stay roughly constant over the mission, but the relative contribution of solar wind ions and cometary ions changes drastically depending on the spacecraft position in the ionosphere and distance from the comet to the sun. We also see that the magnetic pressure, calculated from the magnetic field measured by the Rosetta magnetometer, is on the order of the total ion momentum flux and roughly corresponds with the cometary ion momentum flux. Near both the beginning and end of the mission, solar wind momentum and energy flux are roughly two orders of magnitude larger than the corresponding heavy cometary ion fluxes. When the spacecraft enters the solar wind ion cavity near the comet’s periapsis, the solar wind energy and momentum flux drop drastically, mainly due to reduced density. Meanwhile, the cometary energy flux increases to be roughly equal to the solar wind flux earlier in the mission and the cometary momentum flux as measured by ICA becomes roughly an order of magnitude higher than previous and later solar wind fluxes. We also examine the changes in flux on two excursions, one on the dayside and one on the nightside of the comet, and see that during the nightside excursion, the cometary ion fluxes drop off roughly with the square of the distance from the comet. During the dayside excursion the flux was approximately constant, indicating that the excursion distance was small compared to the region where the observed ions were produced. ICA does not measure the lowest energy ions, so we also discuss the energy and momentum of the full ion population based on density estimates from the LAP and MIP instruments.
Anomalously deep earthquakes in the March 2018 swarm along the Western Margin of Afar
Authors: La Rosa Alessandro , Doubre Cecile , Pagli Carolina , Sani Federico , Corti Giacomo , Leroy Sylvie , Ahmed Abdulhakim , Ayele Atalay , Keir Derek
Published: March 2020

During the evolution of continental rift systems, extension focuses along on-axis magmatic segments while extensional structures along the rift margins seem to progressively become inactive. However, how strain is partitioned between rift axes and rift margins is still poorly understood. The Afar Rift is the locus of extension between Nubia, Arabia and Somalia and is believed to record the latest stages of rifting and incipient continental break-up. The Afar rift axis is bounded at its western margin by a seismically active system of normal faults separating the Afar depression from the Ethiopian Plateau through a series of large bounding faults and marginal grabens. Although most of the extension in Afar is currently accommodated on-axis, several earthquakes with Mw > 5.0 occurred in the past decades on the Western Afar Margin (WAM). Here we analysed the most recent Mw 5.2 earthquake on the WAM on 24 March 2018 and the following seismic sequence using data recorded by a temporary seismic network, set up between 2017 and 2018. We located 800 events from the 20 March to the 30 April 2018 using twenty-three local seismic stations and a new velocity model for the WAM based on a new receiver function study. Preliminary results show that seismicity during the 2018 event focused at mid-to-low crustal depths (from ~15 km to ~35 km) along west-dipping fault planes. Shallower upper crustal earthquakes also occurred on west-dipping fault planes.

The hypocentral location of the mainshock has also been investigated using InSAR. We processed four independent interferograms using Sentinel-1 data acquired from a descending track. None of them shows any significant surface deformation, confirming the large depth of the hypocenters. Furthermore, we tested possible ranges of depth by producing a series of forward models assuming fault located at progressively increasing depths and corresponding to a Mw 5.2 earthquake. Our models show that surface deformations are < 1 cm at depths greater than 15 km, in agreement with our hypocentral depth of 18 km for the main shock estimated from seismic data. 

Our seismicity observations of slip along west-dipping faults show that deformation across the WAM is currently accommodated by antithetic faulting, as suggested by structural geology studies. Lower crustal earthquakes might occur in a strong lower crust due to the presence of mafic lower crust and/or be induced by migrating fluids such as magma or CO2.
Observing Microstructure with Seagliders
Authors: Damerell Gillian , Hall Rob , Sheehan Peter
Published: March 2020

In recent years the UEA glider group worked with Kongsberg Maritime and Rockland Scientific Inc. (RSI) to develop and test an integrated microstructure system which could be mounted on Seagliders.   Existing RSI microstructure packages such as the MicroRider could not be used on Seagliders because of a geometry mismatch with the shape of the Seaglider’s hull that made mounting difficult, and because the size of those packages added an unacceptable drag.  We also required a more sophisticated software interface so that the RSI system could be controlled by the standard Seaglider scientific logger payload control software.

 

Since the initial sea trials in 2015, microstructure Seagliders have been deployed on missions in the Bay of Bengal, the Faroe Shetland Channel, east of the Bahamas, and the Weddell Sea.  Early successes were followed by a number of technical problems which have now been resolved.  Improvements in the glider flight model have led to improvements in microstructure estimates.  The most recent deployment in the Weddell Sea allowed comparison between Seaglider estimates of dissipation and those from an established microstructure profiler (MSS90).  Dissipation estimates measured by the Seaglider system varied between 10-10 and 10-5 W kg-1, with higher values generally closer to the surface.  Those observed by the MSS were similar at depth but slightly higher in the top 200 m.  Further work will aim to understand these differences.
Detecting the signature and transformations of water from coastal permafrost thaw in the Beaufort Sea
Authors: Chaillou Gwénaëlle , Kipp Lauren , Bélanger Frederik , Whalen Dustin
Published: March 2020

The Canadian Beaufort Sea is experiencing coastal erosion at unprecedent rates due to waves impacts and permafrost thaw. Water derived from permafrost thaw has profound impacts on coastal hydrogeology and carbon dynamics. The quality and volume of permafrost water (as surficial and groundwater) discharging to the ocean controls on coastal water chemistry and turbidity. These disturbances alter coastal ecosystems and endanger species with ecological, cultural, and economic value. Robust estimates of these solute and solid inputs are needed on a site-specific scale to obtain accurate regional and global estimations. However, the determination of appropriate endmembers to estimate these fluxes is not straightforward; and yet, little is known about the chemical composition and reactivity of carbon, nutrients and metals of water in coastal permafrost settings. The main objective here is to trace permafrost-derived solutes and study their transport and transformation to coastal water. Several coastal permafrost slumps were visited last summer in the Tuktoyaktuk Peninsula region. Melting-ice, surficial and groundwater were collected to systematically measure short-live isotopes (Rn-222, Ra-223, Ra-224), the stable isotopes of water (δ18O, δD), dissolved organic and inorganic carbon (DOC and DIC), chromophoric component of the organic matter (CDOM), total and non-carbonate alkalinity. In front of these systems, surface seawater samples were collected to 1 to 2 km from the shore to trace these chemical inputs to the coastal ocean. Preliminary results will be presented with a specific focus on the geochemical signature of waters at the nearshore. This project is a part of the WP4 Nunataryuk Program, in collaboration with Natural Resources Canada
Nonstationary Bi-Variate Frequency Analysis of Extreme Sea Level and Rainfall Under Climate Change Impacts: South Carolina Coastal Area
Authors: Golian Saeed , Razmi Ali , Mardani Heydar Ali , Zahmatkesh Zahra
Published: March 2020

Statistical analysis of hydrologic variables is of great importance for water resources systems. Design and operation of these systems is often based on the assumption of data stationarity. However, long-term average of variables such as rainfall as well as sea level is observed to shift over time, mostly attributed to the climate change. These changes, in turn, affect flood volume, peak value and frequency. In this study, a framework was proposed for bi- variate frequency analysis of extreme sea level and rainfall. The analysis was performed on rainfall for the coastal area of Charleston and Savannah, and sea level for the coastal area of Charleston and Fort Pulaski, South Carolina, USA. Extreme values were selected based on the peak over threshold method. To determine the most appropriate distribution, AIC and BIC goodness of fit tests were used. Frequency analysis was then carried out using nonstationary Generalized Extreme Value probability distribution function. Results showed an increase in the sea level long term average, significant trends and outliers (specifically in recent decades), while although the analysis of rainfall data confirms the presence of outliers in the time series, it does not indicate significant trends or heterogeneity. Therefore, in performing bi-variate frequency analysis of extreme rainfall and sea level, non-stationary approaches should be used to provide a more reliable prediction of the joint probability of these variables.