bluuebunny/crossref_metadata_2025 huggingface dataset:
Subseasonal prediction of springtime Pacific-North American transport using upper-level wind forecasts
Authors: Albers John R. , Butler Amy H. , Breeden Melissa L. , Langford Andrew O. , Kiladis George N.
Published: March 2021

Mass transport is important to many aspects of Pacific-North American climate, including stratosphere-to-troposphere transport of ozone to the planetary boundary layer, which has negative impacts on human health, and water vapor transport, which contributes to precipitation variability. Here, subseasonal forecasts (forecasts 3-6 weeks into the future) of Pacific jet variability are used to predict stratosphere-to-troposphere transport (STT) and tropical-to-extratropical moisture exports (TME) during boreal spring over the Pacific-North American region. To do this, we consider a very simple conditional probability: if 200 hPa zonal winds have a high (positive or negative) loading on a particular 200 hPa Pacific basin zonal wind pattern, then what will the corresponding shift in the probability of STT or TME be during those time periods? We first answer this question in the context of a retrospective analysis, which allows us to understand the regionality of STT and TME for different jet patterns. Then, using the retrospective results as a guide, we utilize zonal wind hindcasts from the European Centre for Medium-Range Weather Forecasts Integrated Forecasting System (taken from the S2S Prediction Project) to test whether STT and TME over specific geographic regions may be predictable for subseasonal forecast leads (weeks 3-6). For both analyses, STT and TME are taken from the ETH-Zürich Feature-based climatology database, which allows us to apply a single, self-consistent measure of transport for both the retrospective (1979-2016) and hindcast (1997-2016) analysis periods.

We find that large anomalies in STT to the mid-troposphere over the North Pacific, TME to the west coast of the United States, and TME over Japan are found to have the best potential for subseasonal predictability using upper-level wind forecasts. STT to the planetary boundary layer over the intermountain west of the United States is also potentially predictable for subseasonal leads, but likely only in the context of shifts in the probability of extreme events. While STT and TME forecasts match verifications quite well in terms of spatial structure and anomaly sign, the number of anomalous transport days is underestimated compared to observations. The underestimation of the number of anomalous transport days exhibits a strong seasonal cycle, which becomes progressively worse as spring progresses into summer.
Bayesian Variational Seismic Tomography using Normalizing Flows
Authors: Zhao Xuebin , Curtis Andrew , Zhang Xin
Published: March 2021

Seismic travel time tomography is used widely to image the Earth's interior structure and to infer subsurface properties. Tomography is an inverse problem, and computationally expensive nonlinear inverse methods are often deployed in order to understand uncertainties in the tomographic results. Monte Carlo sampling methods estimate the posterior probability distribution which describes the solution to Bayesian tomographic problems, but they are computationally expensive and often intractable for high dimensional model spaces and large data sets due to the curse of dimensionality. We therefore introduce a new method of variational inference to solve Bayesian seismic tomography problems using optimization methods, while still providing fully nonlinear, probabilistic results. The new method, known as normalizing flows, warps a simple and known distribution (for example a Uniform or Gaussian distribution) into an optimal approximation to the posterior distribution through a chain of invertible transforms. These transforms are selected from a library of suitable functions, some of which invoke neural networks internally. We test the method using both synthetic and field data. The results show that normalizing flows can produce similar mean and uncertainty maps to those obtained from both Monte Carlo and another variational method (Stein varational gradient descent), at significantly decreased computational cost. In our tomographic tests, normalizing flows improves both accuracy and efficiency, producing maps of UK surface wave speeds and their uncertainties at the finest resolution and the lowest computational cost to-date, allowing results to be interrogated efficiently and quantitatively for subsurface structure.
The influence of ionospheric neutral wind variations on the propagation of a MSTID event
Authors: Luo Ji , Xu Jiyao , Wu Kun , Wang Wenbin , Xiong Chao , Yuan Wei
Published: March 2021

The event reports a special case of the propagation and morphology of medium scale travelling ionospheric disturbances (MSTIDs) over middle–latitude China. The MSTIDs were simultaneously observed by the all-sky imager, Swarm satellite, as well as the total electron content (TEC) from global positioning system (GPS). In addition, the MSTIDs lasted for about 6 hours of the field view of airglow imager, the continuous imagers show that the inclination angles of phase fronts were decreasing gradually during the propagation process, resulting in the propagation direction changed from southwestward to nearly westward. More interestingly, the MSTIDs began to dissipate in the airglow observation when they propagated to lower latitudes with the MSTIDs at higher latitudes still visible in the later times. The simulation results from the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) and the Fabry-Perot Interferometer (FPI) wind observations suggest that the variations of background neutral winds and the ionospheric density might play important roles in the changes of propagation direction and the dissipation of MSTIDs.
Why are lightning super-bolts more frequent in East Mediterranean winter thunderstorms?
Authors: Yair Yoav , Price Colin , Namia-Cohen Yannai , Lynn Barry , Shpund Jacob , Yaffe Mordechai
Published: March 2021

The distribution of cloud-to-ground lightning energies is well established, and its most extreme values appear only in extremely rare flashes (< 0.0001%), defined as lightning "super-bolts". There are varying definitions of the specific energy values of super-bolts, depending on the detector or mode of observation. When using optical energy as viewed from a satellite, one usually refers to the brightest flashes (103 times brighter than average), while when relating to the electromagnetic radiation received by lightning detection networks, the definition revolves around the strongest signals in the VLF or ELF range, or the largest peak-current or charge-moment-change (CMC) inferred from the signal. These are all different metrics for evaluating the lightning's intensity, and they are inter-related and exhibit mutual dependence (e.g. extreme values of peak current positively correlate with extreme VLF amplitudes). The global distribution of these extremely powerful lightning is remarkably different from that of normal lightning, which are concentrated in the 3 convective "chimneys" of tropical Africa, South-America and the maritime continent in South-east Asia. Superbolts are found mostly over the oceans and near coastlines, such as Sea of Japan, the North Sea and in the Andes mountains (Holzworth et al., 2019). They are also discovered in maritime winter storms over the Mediterranean Sea which is one of the most prolific regions, especially in the months November-January. We present the climatology of east-Mediterranean super-bolts (peak current > 200 kA), and compare data obtained by various lightning detection networks (ENTLN, WWLLN and ILDN). Some storms exhibit a larger percentage of superbolts compared with the global average, up to 0.65% of total flashes. While the physical mechanisms producing these powerful flashes remains unknown, we suggest that such flashes are more common when large amounts of desert dust aerosols, coming from the Sahara Desert, are ingested into maritime winter storms and contribute to convective invigoration, enhanced freezing and efficient charge separation. Initial modelling results will be discussed.
Environmental change across the onset of the Messinian salinity crisis in the northern Mediterranean (Piedmont Basin, NW Italy)
Authors: Sabino Mathia , Natalicchio Marcello , Birgel Daniel , Dela Pierre Francesco , Peckmann Jörn
Published: March 2021

In the late Miocene, the Mediterranean Basin became a restricted basin because of its progressive tectonic isolation from the Global Ocean. The almost complete halt of the Atlantic-Mediterranean water exchange about 6 Ma ago triggered the deposition of the Mediterranean Salt Giant during the Messinian salinity crisis (MSC; 5.97-5.33 Ma). The environmental conditions, which developed at the onset and during the MSC, are still debated since the evaporites buried beneath the modern Mediterranean seafloor are mostly inaccessible and the marginal successions contain scarce or no body fossils. Aiming to improve our knowledge on the environmental conditions at the onset of the MSC, we investigated the sedimentary record of intermediate palaeobathymetric settings (200-1000 m) from the Piedmont Basin (NW Italy) through a multidisciplinary approach (petrography, organic geochemistry). Shale/marl couplets deposited after the MSC onset are lateral time equivalents of shallow water (<200 m) shale/gypsum couplets deposited during the first phase of the crisis (5.97-5.60 Ma). Our results suggest that the MSC onset coincided with an intensification of water column stratification, most likely favoured by enhanced freshwater input due to moister climate conditions. No evidence of hypersaline conditions was found at the onset of the crisis, but rather normal marine conditions seem to have persisted at least in the upper water column, influenced by freshwater discharge. A stable chemocline apparently separated an upper water layer from a stagnant deeper-water body typified by reducing conditions. These physicochemical changes in the water column governed the sedimentary facies distribution during the first phase of the MSC.
Multi-step wind variability prediction based on deep learning neural network
Authors: Roy Sayahnya
Published: March 2021

Wind energy is widely used in renewable energy systems but the randomness and the intermittence of the wind make its accurate prediction difficult. This study develops an advanced and reliable model for multi-step wind variability prediction using long short-term memory (LSTM) network based on deep learning neural network (DLNN). A 20 Hz Ultrasonic anemometer was positioned in northern France (LOG site) to measure the random wind variability for the duration of thirty-four days. Real-time turbulence kinetic energy is computed from the measured wind velocity components, and multi-resolution features of wind velocity and turbulent kinetic energy are used as input for the prediction model. These multi-resolution features of wind variability are extracted using one-dimensional discrete wavelet transformation. The proposed DLNN is framed to implement multi-step prediction ranging from 10 min to 48 h. For velocity prediction, the root mean square error, mean absolute error and mean absolute percentage error are 0.047 m/s, 0.19 m/s, and 11.3% respectively. These error values indicate a good reliability of the proposed DLNN for predicting wind variability. We found that the present model performs well for mid-long-term (6-24h) wind velocity prediction. The model is also good for the long-term (24-48h) turbulence kinetic energy prediction.
RUSLE Model based Assessment of Soil Erosion in Parbati River Basin, Central India using Google Earth Engine and GIS
Authors: Kumar Rohit , Deshmukh Benidhar , Sathunuri Kiran
Published: March 2021

Land degradation is a global concern posing significant threat to sustainable development. One of its major aspects is soil erosion, which is recognised as one of the critical geomorphic processes controlling sediment budget and landscape evolution. Natural rate of soil erosion is exacerbated due to anthropogenic activities that may lead to soil infertility. Therefore, assessment of soil erosion at basin scale is needed to understand its spatial pattern so as to effectively plan for soil conservation. This study focuses on Parbati river basin, a major north flowing cratonic river and a tributary of river Chambal to identify erosion prone areas using RUSLE model. Soil erodibility (K), Rainfall erosivity (R), and Topographic (LS) factors were derived from National Bureau of Soil Survey and Land Use Planning, Nagpur (NBSS-LUP) soil maps, India Meteorological Department (IMD) datasets, and SRTM30m DEM, respectively in GIS environment. The crop management (C) and support practice (P) factors were calculated by assigning appropriate values to Land use /land cover (LULC) classes derived by random forest based supervised classification of Sentinel-2 level-1C satellite remote sensing data in Google Earth Engine platform. High and very high soil erosion were observed in NE and NW parts of the basin, respectively, which may be attributed to the presence of barren land, fallow areas and rugged topography. The result reveals that annual rate of soil loss for the Parbati river basin is ~319 tons/ha/yr (with the mean of 1.2 tons/ha/yr). Lowest rate of soil loss (i.e. ~36 tons/ha/yr with mean of 0.22 tons/ha/yr) has been observed in the open forest class whereas highest rate of soil loss (i.e. ~316 tons/ha/yr with mean of 32.08 tons/ha/yr) have been observed in gullied area class. The study indicates that gullied areas are contributing most to the high soil erosion rate in the basin. Further, the rate of soil loss in the gullied areas is much higher than the permissible value of 4.5–11 tons/ha/yr recognized for India. The study helps in understanding spatial pattern of soil loss in the study area and is therefore useful in identifying and prioritising erosion prone areas so as to plan for their conservation.
Cloudiness and Earth's hemispheric albedo symmetry
Authors: Datseris George , Stevens Bjorn
Published: March 2021

Radiation measurements at the top of the atmosphere show that the two hemispheres of Earth reflect the same amount of shortwave radiation in the long time average (so-called hemispheric albedo symmetry). Here we try to find the origin of this symmetry by analyzing radiation data directly, as well as cloud properties. The radiation data, while being mostly noise, hint that a hemispheric communication mechanism is likely but do not provide enough information to identify it. Cloud properties allow us to define an effective cloud albedo field, much more useful than the commonly used cloud area fraction. Based on that we first show that extra cloud albedo of the SH exactly compensates the extra surface albedo of the NH. We then identify that this this compensation comes almost exclusively from the storm tracks of the extratropics. We close discussing the importance of approaching planetary albedo as a whole and open questions that remain.
An Imaging Capable, Low Cost IoT Node for River Flood Phenomena
Authors: Skoubris Evangelos , Hloupis George
Published: March 2021

Among all natural disasters, river floods are becoming increasingly frequent. They present high risk and their impact can be fairly destructive and of strong economic, health, and social importance. Key tools to avoid their catastrophic results are the Early Warning Systems (EWS). An EWS usually monitors various physical quantities through a specific hardware, and produce data which after certain processing can detect and estimate the level of the risk.

In the current work we present the concept, the design, the application, and some preliminary data regarding a low cost imaging node, part of an EWS aimed for river floods. This EWS consists of various sensing nodes which are mainly equipped with water presence detectors, water level meters, water temperature sensors, along with the necessary networking capability. The novelty of this new node design is that it utilizes a VGA resolution camera which captures still images of a view of interest. The latter can be for example an implementation prone to defects in case of flood, such as a river basin level road crossing, or a bridge. The images can also provide constant monitoring of the river basin state, i.e. to detect the presence of any unwanted objects (waste or other natural & artificial bring materials). Through image processing the images can even provide some coarse data, i.e. water level measurements by utilizing vertical stripped rods within the field of view of the camera.

The ability to have a camera usually counteracts the IoT characteristics of an electronic device. Nevertheless, in this design the IoT character of the node was not constrained. The nodes have extended power autonomy (several months via Li-Ion battery, optionally solar rechargeable), present a small size, each node is network independent using GSM and LoRaWAN technology. The data usage is minimized by uploading only 2 QVGA images per day in normal operation (can be increased to a maximum of 48 VGA images per day, if required). In case of risk detection the node also supports the actuation of a local warning sign.
Determination of oil charge timing in the Ordovician carbonate reservoir of the Tahe Oilfield, Tarim Basin, NW China
Authors: Chen Jiaxu , Guo Xiaowen
Published: March 2021

Determining the timings of oil charge in sedimentary basins are essential to understand the evolutionary histories of petroleum systems, especially in sedimentary basins with complicated tectonic evolution and thermal histories. The Ordovician carbonate reservoir in the Tahe Oilfield, which is located in the northern Tarim Basin, comprises the largest marine reservoirs in China with reserves up to 3.2×108 t. This study aims to determine the timings of oil charge in the Ordovician carbonate reservoir in the Tahe Oilfield, Tarim Basin, which basin is subjected to multiple phases of tectonic deformations and oil charge. The phases of calcite veins that contain oil inclusions were systematically investigated by cathodoluminescence observation, in situ rare earth element, C, O, and Sr isotope analyses. The homogenization temperatures of aqueous inclusions that are coeval with oil inclusions were measured to determine the timings of oil charge by combining the burial and geothermal histories. Two phases of calcite veins were judged by the differences in cathodoluminescence color, Ce anomaly, δ18O, and 87Sr/86Sr values, which might be caused by variations in the water-rock interaction processes during different calcite phases. Primary oil inclusions with yellow fluorescence were observed in the two phases of calcite veins, suggesting two phases of oil charge. By combining the homogenization temperatures of aqueous inclusions with the burial and geothermal histories, the timing of phase I oil charge was inferred to be 336–312 Ma, and the timing of phase II oil charge was inferred to be 237–217 Ma.
A search for constraints on lithospheric net rotation in 2D convection simulations
Authors: Atkins Suzanne , Coltice Nicolas
Published: March 2021

Net rotation is the process whereby the entire lithosphere can rotate with respect to the Earth’s mantle. The plates and continents retain their location with respect to each other, but they change their position with respect to global reference frames such as the Earth’s magnetic dipole, and structures in the Earth’s mantle such as plumes and hotspots. Constraining lithospheric net rotation is therefore one factor in building an absolute plate motion model. However, the amount of net rotation occurring at present day is poorly contained, and the drivers of net rotation are very poorly understood. Many absolute plate motion models therefore attempt to minimise net rotation, because there is no way to constrain rotation in the geological past. 

 

In previous geodynamical studies, the presence of thick continents and large viscosity contrasts were found to be controlling factors in the development of net rotation. We investigate the effects of different convection parameters and tectonic states on the magnitude and evolution of net rotation in 2D simulations. The use of 2D simulations allows us to run enough simulations to study a wide range of model parameters. We intend to compare our 2D conclusions with 3D simulations, to investigate how much of a difference the third dimension makes.

 

We find that net rotation varies on much shorter timescales than any other geodynamic feature. Net rotation is not cleanly correlated with any tectonic behaviours or settings, and that the magnitude and duration is unpredictable. We do however find that the distribution of net rotation within the lifetime of a particular simulation is Gaussian, with standard deviation dependent on the viscosity structure and contrasts of the simulation, in agreement with previous studies. However, in contrast to previous studies, the presence and thickness of continents makes very little difference to the speed of lithospheric rotation, although this may be because we are working in 2D. If the 2D results are also relevant in 3D, net rotation is a continuously varying and unpredictable value, but with a predictable statistical range. This may provide a way to better constrain net rotation for plate motion models.
Bayesian multiple rupture plane inversion to assess rupture complexity: application to the 2018 Mw 7.9 Alaska earthquake
Authors: Carrillo Ponce Angela , Dahm Torsten , Cesca Simone , Tilmann Frederik , Babeyko Andrey , Heimann Sebastian
Published: March 2021

When the earthquake rupture is complex and ruptures of multiple fault segments contribute to the total energy release, the produced wavefield is the superposition of individual signals produced by single subevents. Resolving source complexity for large, shallow earthquakes can be used to improve ground shaking and surface slip estimations, and thus tsunami models. The 2018 Mw 7.9 Alaska earthquake showed such complexity: according to previous studies, the rupture initiated as a right-lateral strike-slip fault on a N-S oriented fault plane, but then jumped onto a left-lateral strike-slip fault oriented westward. Rupture complexity and presence of multiple subevents may characterize a number of other earthquakes. However, even when individual subevents are spatially and/or temporally separated, it is very difficult to identify them from far field recordings. In order to model complex earthquakes we have implemented a multiple double couple inversion scheme within Grond, a tool devoted to the robust characterization of earthquake source parameters included in the Pyrocko software. Given the large magnitude of the target earthquake, we perform our source inversions using broadband body waves data (P and S phases) at teleseismic distances. Our approach starts with a standard moment tensor inversion, which allows to get more insights about the centroid location and overall moment release. These values can then be used to constrain the double source inversion. We discuss the performance of the inversion for the Alaska earthquake, using synthetic and real data. First, we generated realistic synthetic waveforms for a two-subevents source, assuming double couple sources with the strike-slip mechanisms proposed for the Alaska earthquake. We model the synthetic dataset both using a moment tensor and a double double couple source, and demonstrate the stability of the double double couple inversion, which is able to reconstruct the two focal mechanisms, the moment ratio and the relative centroid locations of the two subevents. Synthetic tests show that the inversion accuracy can be in some cases reduced, in presence of noisy data and when the interevent time between subevents is short. A larger noise addition affects the retrieval of the focal mechanism orientations only in some cases, but in general all the parameters were well retrieved. Then, we test our tool using real data for the earthquake. The single source inversion shows that the centroid is shifted 27 s in time and 40 km towards NE with respect to the original assumed location retrieved from the gCMT catalogue. The following double double couple source inversion resolves two subevents with right-lateral and left-lateral strike-slip focal mechanisms and Mw 7.6 and 7.8 respectively. The subevent centroids are separated by less than 40 km in space and less than 20 s in time.
Towards 3D Multiscale Adjoint Waveform Tomography of the Lithosphere and Underlying Mantle beneath Southeast Asia
Authors: Wehner Deborah , Blom Nienke , Rawlinson Nicholas , Miller Meghan , Widiyantoro Sri , Daryono Mr
Published: March 2021

Southeast Asia is one of the most complex tectonic regions on Earth. This is mainly a result of its location within the triple junction of the Australian, Eurasian and Philippine Sea plates which has created a complicated configuration of active plate tectonic boundaries. Adjoint waveform tomography is especially suitable for imaging such complex regions. By simulating the 3D wavefield, it is possible to directly compare observed and simulated seismograms, thereby taking into account both body and surface waves. The method can account for the effects of anisotropy, anelasticity, wavefront healing, interference and (de)focusing that can hamper other seismological methods.

To date, sparse instrument coverage in the region has contributed to a heterogeneous path coverage. In this project, we make use of publicly available data as well as our recently deployed networks of broadband seismometers on Borneo and Sulawesi. This, in addition to access to national permanent networks, provides data from over 300 stations which promises a significant improvement in data coverage around the Banda Arc, Borneo and Sulawesi. We employ a geographical weighting scheme to minimise the effect of dense regional arrays and compile a catalogue of 118 well-constrained earthquakes, optimising for coverage, signal-to-noise ratio and data availability. An optimised window selection algorithm allows us to balance amplitude differences and include as much signal as possible while avoiding noisy data.

Here, we present a seismic waveform tomography for upper mantle structure in Southeast Asia, imaging radially anisotropic S velocity, P velocity and density. We use a gradient-based optimisation scheme (L-BFGS) and adjoint methods to obtain sensitivity kernels as the corresponding gradients. In the first part of the inversion, periods down to 50 s are used to update a 1D initial model, adapting a multi-scale approach in which long periods are inverted for first to avoid cycle skipping. In our long-period results, we observe a strong regional low S-velocity structure with an underlying high-velocity anomaly. The results are consistent with the global S40RTS model. 
Geochemistry of Chromium-Silicate Minerals
Authors: Dall Jacqueline , Oze Christopher , Celestian Aaron , Rossman George
Published: March 2021

Water-rock interactions at elevated pressures and temperatures may mobilize chromium from chromite to produce a variety of Cr-silicate minerals. Common Cr-silicates include fuchsite (KCr2(AlSi3O10)(OH)2), kämmererite ((Mg5Cr)(AlSi3)O10(OH)8), tawmawite (Ca2CrAl2Si3O12(OH)), and uvarovite (Ca3Cr2Si3O12). Here we assess the geochemistry and calculate the thermodynamic properties of a variety of Cr-silicates to elucidate their formation as well as how they may contribute chromium to the environment. Chromium-silicates follow an idealized 1:1 relationship with regards to Cr(III) and octahedral Al, except for kämmererite. Kämmererite can have Al in excess of 1:1 to Cr(III), substituting into the Mg site. FTIR and Raman analyses demonstrate that Cr(III) enrichment is distinguishable between respective end member minerals. Thermodynamic properties were calculated using established estimation algorithms and unit-cell measurements.  Overall, we provide an extensive assessment of Cr-silicates that addresses the formation of Cr-silicates and fate of chromium in the environment.
Closing the climate-hydrology feedback loop: Variations in greenhouse gas fluxes resulting from changes in catchment hydrology due to human-induced climate change
Authors: Comer-Warner Sophie , Brekenfeld Nicolai , Romeijn Paul , Ullah Sami , Gooddy Daren , Kettridge Nicholas , Marchant Benjamin , Hannah David , Mao Feng , Krause Stefan
Published: March 2021

Climate change during the Anthropocene has caused many disturbances to Earth’s system, including altering patterns of precipitation and temperature. This has led to hydrological extremes with increases in both floods and droughts globally. We know and recognise this large effect on the global water cycle, but the consequent influence on biogeochemistry and greenhouse gas production has received less attention. Changes in greenhouse gas emissions due to increases in hydrological extremes may be an unrecognised climate feedback, having large implications for future climate and in turn, catchment hydrology. Here we present a synthesis from field studies and a review of the literature to investigate the effects of hydrological extremes on greenhouse gas production and emissions. We focus on variations in greenhouse gas emissions as a result of changes in both discharge and temperature, which are affected by hydrological extremes.
How much should we increase carbon inputs to the soil to reach a 4per1000 objective of soil organic carbon storage in European agricultural sites: a multi-modelling approach
Authors: Bruni Elisa
Published: March 2021

Anthropogenic greenhouse gases emissions are the main driving force of climate change. They need to be strongly reduced during the next Century until carbon neutrality in order to keep the international 2°C objective of the Paris Agreement on Climate. The “4per1000” initiative was launched in 2015 as a climate mitigation option, with an aspiration to increase global soil organic carbon (SOC) stocks by 4‰ per year to compensate for the anthropogenic emissions of carbon dioxide in the atmosphere. The “4per1000” is not applicable everywhere, hence a full compensation of anthropogenic emissions is unlikely. Nevertheless, where possible, it has been identified as an interesting approach to mitigate climate change and, at the same time, ensure food security through improved soil fertilization. To reach such an objective one must either reduce carbon outputs (e.g. erosion and respiration) or increase the inputs of biomass to the soil.

Here, we use a multi-modelling approach to study the challenges of SOC storage potential through increased organic inputs in agricultural sites. The aim is to respond to the following question: “What is the amount of carbon inputs that needs to be brought to soils as a means to increase SOC stocks by 4‰ per year?” This scientific question belongs to the family of inverse problems and is addressed by using a multi-modelling approach, to improve the predictions and associated uncertainties of model outputs.

The amount of required carbon inputs to reach the 4per1000 is estimated over 30 years of simulations with five different models (Century, RothC, ICBM, AMG and Millennial) and is compared to more than 15 long-term arable experiments of organic matter addition in Europe. This allows estimating the feasibility of a 4per1000 objective in temperate, north-temperate and Mediterranean regions with different treatments of organic matter inputs. As a final step, we evaluate the sensitivity of the predicted carbon inputs requirement to future projections of climate change.

The 4per1000 initiative is an interesting approach to contribute for the mitigation of climate change through agriculture. Here, we will present preliminary results of a multi-modelling analysis showing that the necessary inputs to reach the 4per1000 target are realistic for some experimental conditions, but might be too high to be implemented at a larger scale.
Bayesian Belief Networks for the metamodeling of simulation-optimization model to identify optimum water allocation scenario, Application in Miyandoab plain, Urmia Lake basin, Iran
Authors: Dehghanipour Amirhossein , Schoups Gerrit , Babazadeh Hossein , Ehtiat Majid , Zahabiyoun Bagher
Published: March 2021

In this study, decision-making models in uncertain conditions are developed to identify optimal strategies for reducing competition between agricultural and environmental water demand. The decision-making models are applied to the irrigated Miyandoab Plain, located upstream of endorheic Lake Urmia in Northwestern Iran. Decision-making models are conceptualized based on static and dynamic Bayesian Belief Networks (BBN). The static BBN evaluates the effects of management strategies and drought conditions on environmental flow and agricultural profit at the annual scale, while the dynamic BBN accounts for monthly dynamics of water demand and conjunctive use. The reliability and performance of BBNs depend on the quantity and quality of data used to train the BBN and create conditional probability tables (CPTs). In this study, simulated outputs from a multi-period simulation-optimization model (Dehganipour et al., 2020) are used to populate the CPTs in each BBN and reduce the BBN training error. Cross-validation tests and sensitivity analysis are used to evaluate the effectiveness of the resulting BBNs. Sensitivity analysis shows that drought conditions have the most significant impact on environmental flow compared to other variables. Cross-validation tests show that the BBNs are able to reproduce outputs of the complex simulation-optimization model used for training, and therefore provide a computationally fast alternative for decision-making under uncertainty.

Reference: Dehghanipour, A. H., Schoups, G., Zahabiyoun, B., & Babazadeh, H. (2020). Meeting agricultural and environmental water demand in endorheic irrigated river basins: A simulation-optimization approach applied to the Urmia Lake basin in Iran. Agricultural Water Management, 241, 106353.
Water exchange between estuarine lagoon and sea through a narrow strait: case study of two Brazilian lagoons
Authors: Gordey Alexandra , Osadchiev Alexander
Published: March 2021

The Patos Lagoon, located in the Southern Brazil, is the largest freshwater lagoon in the World (area is 10 360 km2). It is connected with the Atlantic Ocean by a narrow strait, through which saline sea waters inflows to the lagoon and fresh waters of Patos outflows to the sea. Todos os Santos is the second large bay in the Brazil, which area is 1223 km2. It is located in the Northern Brazil, connected with Atlantic Ocean and remains saline during the whole year. Study of these basins represent difference in water exchange mechanisms between small and large estuarine lagoon.
Based on year-long in situ data from sea mooring and river gauge stations, as well as wind and precipitation reanalysis data, the influence of local meteorological and hydrological conditions on water exchange of these basins was studied.
It was revealed that the distinct seasonal variability of water exchange in Patos is defined mostly by the seasonal river discharge variability, while the variability of local atmospheric circulation does not influence it. Outflows of lagoon waters to the sea are typical during the high river discharge period, while inflows of sea waters to the lagoon are rare and occur under specific wind conditions. During the low river discharge periods, inflows of sea waters to the lagoon are typical, while short-term outflows are induced by increase of river discharge.
Meantime, it was found that synoptical salinity variation in Todos-os-Santos is mostly caused by tides, while seasonal water exchange variability is almost generally wind-driven. 
Preliminary biostratigraphy of IODP Expedition 383 sites
Authors: Saavedra-Pellitero Mariem , Brombacher Anieke , Esper Oliver , de Souza Alexandre , Malinverno Elisa , Venancio Igor , Riesselman Christina , Singh Raj K. ,   Expedition 383 Scientists
Published: March 2021

The Antarctic Circumpolar Current (ACC) is a major driver of global climate. It connects all three ocean basins, integrating global climate variability, and its vertical water mass structure plays a key role in oceanic carbon storage. The Atlantic and Indian sectors of the ACC are well studied, but the Pacific sector lacks deep-sea drilling records. Therefore, past water mass transport through the Drake Passage and its effect on Atlantic Meridional Overturning Circulation are not well understood. To fill this gap, IODP Expedition 383 recovered sediments from three sites in the central South Pacific and three sites from the southern Chilean Margin.

Here we present the preliminary biostratigraphy developed during the expedition. The sediments contained abundant nannofossils, foraminifera, radiolarians, diatoms and silicoflagellates which produced age models that were in excellent agreement with the shipboard magnetostratigraphy. Two sites contain high-resolution Pleistocene records, one site goes back to the Pliocene, and two others reach back to the late Miocene. Post-cruise research will further refine these age models through high-resolution bio-, magneto- and oxygen isotope stratigraphies that are currently being generated.
A new representation of conventional hydropower in unit commitment economic dispatch models to support resource adequacy and reliability studies
Authors: Voisin Nathalie , Oikonomou Konstantinos , Turner Sean , Clement Mitch , Magee Tim , Zagona Edith , Ploussard Quentin , Veselka Thomas
Published: March 2021

The Western U.S. relies heavily on hundreds of water-dependent power plants, with hydropower and fresh surface water dependent thermo-electric plants accounting for over 60% of generating capacity.  The Western Interconnect overlays 11 States, over three different electricity market areas, and 9 large river basins with tens of unconnected watersheds as well as tens of coordinated watersheds. Such complexity requires computational tradeoffs for the representation of the water-energy dependencies, including a centrally controlled unit commitment and economic dispatch as well as an offline representation of hydropower’s availability and operations. Benchmark hydropower representations for application to resource adequacy studies include i) fixed daily time series and ii) a parameterized monthly representation involving three constraints: a monthly energy target, and hourly minimum and maximum generation. The representations are derived for one year and under average water conditions. We propose a large-scale approach to represent medium-term (weekly) hydropower flexibility for grid-scale reliability studies, as driven by weekly water availability. Using a combination of hydrological models, reservoir operation schemes, and statistical tools, we develop datasets of hydropower plant-specific weekly energy targets, with weekly minimum and maximum hourly generation, for multiple years with varying water conditions. The assumption – and computational tradeoff - is that water availability guides the weekly operations and range of daily operations, leaving enough flexibility for the power system optimization to accommodate intra-day, week days and weekends load variations. We present the hydropower datasets and evaluate how this new representation influences the simulated contribution of hydropower to grid operations as part of resource adequacy and reliability studies.
Analysis of Secondary Organic Aerosol Simulation Bias in the Community Earth System Model (CESM2.1)
Authors: Liu Yaman , Dong Xinyi , Wang Minghuai , Emmons Louisa , Liu Yawen , Liang Yuan , Li Xiao , Shrivastava Manish
Published: March 2021

Organic aerosol (OA) has been considered as one of the most important uncertainties in climate modeling due to the complexity in presenting its chemical production and depletion mechanisms. To better understand the capability of climate models and probe into the associated uncertainties in simulating OA, we evaluate the Community Earth System Model version 2.1 (CESM2.1) configured with the Community Atmosphere Model version 6 (CAM6) with comprehensive tropospheric and stratospheric chemistry representation (CAM6-Chem), through a long-term simulation (1988–2019) with observations collected from multiple datasets in the United States. We find that CESM generally reproduces the inter-annual variation and seasonal cycle of OA mass concentration at surface layer with correlation of 0.40 as compared to ground observations, and systematically overestimates (69 %) in summer and underestimates (-19 %) in winter. Through a series of sensitivity simulations, we reveal that modeling bias is primarily related to the dominant fraction of monoterpene-formed secondary organic aerosol (SOA), and a strong positive correlation of 0.67 is found between monoterpene emission and modeling bias in eastern US during summer. In terms of vertical profile, the model prominently underestimates OA and monoterpene concentrations by 37–99 % and 82–99 % respectively in the upper air (>500 m) as validated against aircraft observations. Our study suggests that the current Volatility Basis Set (VBS) scheme applied in CESM might be parameterized with too high monoterpene SOA yields which subsequently result in strong SOA production near emission source area. We also find that the model has difficulty in reproducing the decreasing trend of surface OA in southeast US, probably because of employing pure gas VBS to represent isoprene SOA which is in reality mainly formed through multiphase chemistry, thus the influence of aerosol acidity and sulfate particle change on isoprene SOA formation has not been fully considered in the model. This study reveals the urgent need to improve the SOA modeling in climate models.
Determining gravity potential difference via VLBI time comparisons
Authors: Wu Yifan , Shen Wen-Bin
Published: March 2021

VLBI technique plays important role in both astronomy and geodesy due its fantastic ability to determine the position of celestial bodies and the length of baseline on Earth. Moreover it also presents excellent work on time comparisons between atomic clocks located in remote positions where optical fiber links are not accessible. Due to its high reliability and stability, the information of Earth’s gravity field can be extracted from VLBI time comparisons in the framework of general relativity. In this study, we provide a formulation to determine the gravity potential difference by VLBI time comparisons. In fact the precision of the estimated gravity potential depends on the performance of participated clocks and the accuracy of time comparison technique. Thus we present simulation experiments using clocks with 10-16@1d stability and broadband VLBI observation and determine gravity potential difference within a VLBI network around world with 10 m2/s2 precision which is equivalent to 1 m in height. The results could be greatly improved using optical atomic clocks with much higher stabilities. Furthermore it can be applied to height transfer across oceans and unifying the height system. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, and Space Station Project (2020)228.
Sulphur constraints on peatland carbon cycle
Authors: Worrall Fred , Boothroyd Ian , Moody Catherine , Clay Gareth , Abbott Geoff
Published: March 2021

The reduction of sulphate  (SO ) represents an alternative terminal electron acceptor for the oxidation of organic matter in peat soils. The greenhouse gas budget in peatlands will be constrained by how much a peatland can utilise SO4 reduction and provide an alternative to methanogenesis. This study used records of atmospheric deposition and stream chemistry coupled with elemental analysis of peat soil, vegetation and dissolved organic matter (DOM) from streams and soil porewater, to estimate a 23-year long sulphur (S) budget for a blanket bog-covered catchment in the North Pennines, England. The study showed that:

1) Atmospheric deposition of total S significantly declined over the study period from 2.4 to 0.5 t S/km2/yr.

2) Long term accumulation of S into deep peat at 1 m depth averaged 127 kg S/km2/yr.

3) Based upon shallow soil water concentrations the total S fluvial flux peaked as 4.5 t S/km2/yr with an average of 0.7 t S/km2/yr. The flux of total S increased over the catchment suggesting a groundwater source of oxidised S.

4) Over the 23 years of monitoring, 0.25 t S/km2/yr were reduced to either mineral sulphides or hydrogen sulphide; however, in 8 out of the 23 years the catchment was a net producer of S to the streams of the catchment.

At maximum observed S reduction capacity the peatland was capable of a net removal of 71% of atmospheric S deposition. Allowing for the efficiency of energy transfer in the redox process and the oxidation state of peat organic matter means that for every mole of SO4 reduced, 1.69 moles of CO2 were produced and not the 2 moles normally assumed. In this catchment an average of 0.47 t C/km2/yr are diverted from methanogenesis.
Beyond high frequency monitoring: an optimised automatic sampling
Authors: Mougin Jérémy
Published: March 2021

Beyond high frequency monitoring : an optimised automatic sampling

Mougin Jérémy, Superville Pierre-Jean, Cornard Jean-Paul, Billon Gabriel

 

In order to improve the representativity of samples when monitoring a water body, efforts have been made these last years to develop new methodologies to replace grab samples. Passive samplers have allowed to have measurement averaged over several days and represented a first step. High frequency monitoring (usually one measure per hour), either in situ or on-line, led to the observations of daily cycles or transitory phenomena that were not suspected beforehand.

However, such method is usually difficult to implement for some trace analytes (e.g. trace metals or pesticides) or for some specific analysis (e.g. size exclusion chromatography on natural organic matter). Automatic sampling and analysis in the lab can be a solution, but it becomes very labor intensive as soon as the sampling frequency is high. Luck is also needed as a long sampling period can sometimes lead to very few variations if the water system is stable. In order to optimise the automatic sampling, a new methodology has been developped in this project.

A multiparameter probe measuring general parameters (temperature, pH, turbidity, ORP, conductivity, dissolved oxygen and two fluorometers for organic matter) was coupled with an automatic filtering sampler. The data from the probe are processed on-line and an algorithm decides if the geochemical situation in the water body seems new enough to trigger the sampling, based on previously sampled waters. The aim of this device is to collect the right number of samples with the best representativeness of phenomena taking place in the environment.

This method will be tested over a year in 2021 in order to monitor the dissolved organic matter in a small stream with both rural and urban contamination. These high-frequency measurements and samplings could make it possible to better define the sources and dynamics of the organic matter that has a strong impact on the quality of watercourses.