bluuebunny/crossref_metadata_2025 huggingface dataset:
Cascading and the pathways of the key biogeochemical tracers in the Canadian Basin: from models and observations.
Authors: Luneva Maria , Aksenov Yevgeny , Ivanov Vladimir , Kelly Stephen , Tuzov Fedor
Published: March 2020

We explore dense water cascading (DWC; a type of bottom-trapped gravity current) on multi-decadal time scales using a pan-Arctic regional ocean-ice model. DWC is particularly important in the Arctic Ocean as the main mechanism of ventilation of interior waters when open ocean convection is blocked by strong density stratification. We identify the locations where the most intense DWC events occur and evaluate the associated cross-shelf mass, heat and salt fluxes. 

 

A detailed analysis of specific cascading sites around the Beaufort Gyre and adjacent regions is performed. We find that autumn upwelling of warm and saltier Atlantic waters on the shelf and subsequent cooling and mixing of uplifted waters trigger the cascading on the West Chukchi Sea shelf break. We also perform Lagragian particle tacking of low salinity Pacific waters originating at the surface in the Bering Strait; these waters are shown to be modified by brine rejection and cooling, and through subsequent mixing become dense enough to reach depths of 160-200m and below. We examine the role of cascading and shelf upwelling on the shelf waters transformation, pathways and spread of the biological important tracers (O18, Si., DIC snd DIN).
The initial Data Management Plan for PalMod II - FAIR simulation and paleo data from the Last Interglacial to the Anthropocene
Authors: Bothe Oliver , Peters Karsten
Published: March 2020

The project PalMod II is the second phase of Germany’s national paleoclimate modelling initiative (www.palmod.de) whose aim is to model the transient climate evolution from the last interglacial to the anthropocene with state of the art earth system models. The second phase more precisely wants to perform simulations for the last glacial inception, the marine isotope stage 3, and the last deglaciation. It further plans to compile paleo-observational proxy data over the full glacial cycle from about 130,000 years before present until today. Models of differing complexity (fully-coupled earth system models and models of intermediate complexity) will be used to assess the scientific questions posed in PalMod II. Model output will be combined with the compiled paleo-proxy data for validation purposes. The sheer data amount in excess of several petabytes and different data handling practices of the participating communities require dedicated management of the data workflow both in- and outside of the immediate PalMod community.

The PalMod II data management takes place in close collaboration between data management specialists and the scientists. The objectives include the standardisation of each simulation and proxy dataset, the facilitation of data sharing and data reuse between work packages, the access channels for external collaborators, and the long-term preservation of the data. The data management follows the concept of the "Active Data Management Plan", which foresees a continuous development of the data management plan (DMP), starting with an initial basic version. The DMP covers the entire life cycle of the research data generated in the project, from generation and analysis to data publication and archiving. This includes aspects such as data formats, metadata standards and data usage licenses. Ownership and responsibilities for simulation and paleo data sets as well as the input data during and after the end of the project will also be considered.

This contribution will present the initial DMP for PalMod II. It will describe the amount of data produced in the project, highlight how the above mentioned aspects will be dealt with, and present how the project aims to ensure the Findability, Accessibility, Interoperability, and Reusability, i.e. the FAIR data principles, of simulation output, post-processed model data, and paleo-proxy data from PalMod II.

* This contribution presents results of the full PalMod II initiative, the authors present them on behalf of the initiative.
Size Distribution and Depolarization Properties of Aerosol Particles over the Northwest Pacific and Arctic Ocean from Shipborne Measurements during an R/V Xuelong Cruise
Authors: Pan Xiaole , Tian Yu , Yan Jinpei , Lin Qi , Sun Yele , Fu Pingqing , Wang Zifa
Published: March 2020

Atmospheric aerosols over polar regions have attracted considerable attention for their pivotal effects on climate change. In this study, temporospatial variations in single-particle-based depolarization ratios (δ: s-polarized component divided by the total backward scattering intensity) were studied over the Northwest Pacific and the Arctic Ocean using an optical particle counter with a depolarization module. The δ value of aerosols was 0.06 ± 0.01 for the entire observation period, 61 ± 10% lower than the observations for coastal Japan (0.12 ± 0.02) (Pan et al. Atmos. Chem. Phys. 2016, 16, 9863−9873) and inland China (0.19 ± 0.02) (Tian et al. Atmos. Chem. Phys. 2018, 18, 18203−18217) in summer. The volume concentration showed two dominant size modes at 0.9 and 2 μm. The super-micrometer particles were mostly related to sea-salt aerosols with a δ value of 0.09 over marine polar areas, ∼22% larger than in the low-latitude region because of differences in chemical composition and dry air conditions. The δ values for fine particles (<1 μm) were 0.05 ± 0.1, 50% lower than inland anthropogenic pollutants, mainly because of the complex mixtures of sub-micrometer sea salts. High particle concentrations in the Arctic Ocean could mostly be attributed to the strong marine emission of sea salt associated with deep oceanic cyclones, whereas long-range transport pollutants from the continent were among the primary causes of high particle concentrations in the Northwest Pacific region.
Improved SLR orbit validation for Copernicus Sentinel-3 mission
Authors: Fernández Marc , Raposo Virginia , Fernández Sánchez Jaime , Peter Heike , Féménias Pierre
Published: March 2020

The European Copernicus Sentinel-3 mission, a jointly operated mission by ESA and EUMETSAT, consists of two satellites equipped with GPS and DORIS receivers, and a Laser Retro Reflector (LRR) array, which allows tracking the satellites by Satellite Laser Ranging (SLR). The SLR observations are mainly used for the validation of GPS- and/or DORIS-derived precise orbit solutions. The SLR residuals are derived from the simple difference between observed and computed range between SLR station and the satellite. Only a subset of the SLR stations tracking the satellites is normally used for this purpose. The subset consists of stations delivering good quality observations on a long-term. The station selection is regularly reviewed to guarantee a continuous quality for the orbit validation.

Instead of using only a subset of the stations it would be preferable to use as many laser tracking data as possible. Long-term and highly accurate orbit time series of low Earth orbiting satellites can be used to estimate station range biases. The SLR validation is significantly improved by adding these station range biases due to additional stations and due to the removal of SLR related systematic patterns.

In the Copernicus POD Service (CPOD), the SLR station range biases are estimated based on a combined Sentinel-3A and -3B orbits computed from different orbit providers (the CPOD Quality Working Group). Performance, quality, mission dependency and stability of these SLR station range biases are analysed based on operational CPOD orbits and orbit solutions delivered by the Copernicus POD Quality Working Group.
High-resolution catalog of the the Maurienne Swarm (French Alps) based on template matching and double-different relocation
Authors: Minetto Riccardo , Helmstetter Agnès , Guéguen Philippe , Langlais Mickael , Coutant Olivier , Schwartz Stéphane , Janex Gaël , Nomade Jérôme , Dumont Thierry
Published: March 2020

Since 2017, the Maurienne Valley (French Alps) has been affected by an episode of seismic unrest. In this study we focused on the seismic swarm that occurred in 2017 and 2018, which was characterized by 8 events with ML > 3 and a maximum magnitude of 3.7. The goal was to extend the existing SISmalp catalog, and also to provide accurate locations and magnitude estimations.

The employed data was recorded by a local seismic network composed of 6 broadband stations. The use of template matching allowed us to detect more than 70000 events, increasing the detection rate by more than ten times compared to the original catalog. We obtained high resolution locations applying a double difference relocation method, providing as input differential times calculated by cross-correlating templates with their respective detections. Finally, we estimated magnitudes using template-family-based linear regression analysis, in order to include even the weakest events. The seismic locations will be discussed in the tectonic and geological setting of the Maurienne Valley.
Identifying canopy-scale adjustments to the extreme climate in a semi-arid pine forest using eddy covariance and close-range sensing data
Authors: Wang Huanhuan , Gitelson Anatoly , Sprintsin Michael , Rotenberg Eyal , Yakir Dan
Published: March 2020

Semi-arid forests represent some of the most sensitive ecosystems to climate change. Identifying adjustments to extreme conditions can indicate their resilience, and that of forests undergoing increasing aridity trends. We used eddy covariance and close-range sensing measurements over four years in a semi-arid pine forest to identify canopy-scale adjustments to the short active season and long seasonal drought. Peaks in light use efficiency (LUE), leaf chlorophyll content (LCC), and increasing absorbed photosynthetic active radiation (APAR; based on canopy absorption coefficient in the green range), all converged to support an early peak (March) in gross primary productivity (GPP), exploiting the narrow optimum between PARin, temperature and the rapidly decreasing soil moisture in spring. In contrast, during the long dry period (>200 days), while PARin increased, LCC and LUE decreased, offering physiological photoprotection as GPP sharply declined under the stressful conditions. The strong negative correlation between ρNIR and PARin indicated canopy biophysical adjustments that enhance light absorption under low radiation and eliminate photodamage under excessive radiation.  The results provide clear indications of canopy-scale adjustments underlying the high productivity of the forest and its resistance to the harsh conditions, which may soon apply to forests in currently milder climatic regions.
Anthropogenic salinization of naturally dilute boreal lakes in Finland
Authors: Tammelin Mira , Kauppila Tommi , Mäkinen Jari
Published: March 2020

Recent findings from North America and Europe suggest that anthropogenic salinization of freshwaters is an emergent threat in the Northern Hemisphere. Causes of salinization include irrigation, water abstraction, resource extraction, land clearing and accelerated weathering, road de-icing, and sewage. Our study shows that freshwater salinization is not only restricted to arid and temperate regions, but is also evident in dilute boreal lakes located on the slowly weathering, mainly granitic and gneissic bedrock of the Fennoscandian Shield. We used quantitative paleolimnology to study natural as well as present-day diatom assemblages and diatom-inferred epilimnetic electrical conductivity (a proxy for salinity) of 70 lakes in southern and central-eastern Finland.

According to our results, electrical conductivity increased from natural to present-day conditions in 61 of the 70 lakes, most likely due to agriculture and urbanization. In these 61 lakes, the maximum increase was 11.7 mS m-1 and average increase was 3.0 mS m-1, both notable compared to the natural variation between lakes ranging from 2.3 to 7.2 mS m-1 (average 3.8 mS m-1). Natural electrical conductivities were higher in lakes located on the clayey coast of Finland than in lakes further inland characterized by catchments rich in sandy till. In conclusion, our study 1) establishes an estimate of natural salinity variation in dilute boreal lakes overlying acidic bedrock, 2) emphasizes that boreal lakes are also threatened by freshwater salinization, and 3) promotes the importance of management actions targeted to prevent freshwater salinization.
Manure happens: re-examining mitigation potential from waste-to-resource in agricultural ecosystems
Authors: Qin Zhangcai
Published: March 2020

Using animal waste (manure) for soil amendments have been recognized as an efficient strategy for farm management, as well as for soil preservation and greenhouse gas (GHG) emissions mitigation. It is believed that manure can improve soil quality, increase soil organic carbon (SOC) level and therefore potentially mitigate GHG emissions. However, recent studies reported that use of manure in the field can cause large amount of nitrous oxide (N2O) emissions which in many cases offset the amount of SOC sequestered in agricultural ecosystems and eventually lead to net GHG emissions. In this report, we intended to investigate this management related mitigation option holistically, by modeling the full GHG budgets from a life cycle perspective. GHG emissions and some reactive gases (e.g., VOCs, NO) were specifically included in the manure life cycle. By re-examining the system boundary in previous studies, we show that use of manure does not necessarily cause large GHG emissions as previously reported. Net GHG emissions or mitigation potentials depend on not only SOC and N2O emissions in situ, but also emissions and reactive gases beyond the farmgate and those would have been released anyway.
Shallow-depth slab decarbonation prevents recharge of the deep carbon cycle
Authors: Strobl Leonie , Beinlich Andreas , Ohl Markus , Plümper Oliver
Published: March 2020

Long-term oscillations of the Earth’s atmospheric carbon dioxide concentration and climate are intrinsically linked to tectonic plate motion controlling CO2 uptake in rocks, their transport into the Earth’s mantle and recycling back into the atmosphere by volcanic activity. In this long-term deep carbon cycle, the efficiency of mantle ingassing is controlled by the stability of carbon carrier phases at subduction zone pressure-temperature conditions, during deformation and their interaction with subduction zone dehydration fluids. However, the current understanding of carbonate stability under these conditions is controversial. This is reflected by studies predicting carbonate transport deep into the asthenospheric mantle [1, 2] in contrast to more recently postulated shallow-depth carbon release from subducting slabs [e.g. 3]. Some of this controversy is related to the lack of available field sites that allow for the quantification of subduction-related decarbonation and its driving force. Here we present novel observations on the release of carbon during subduction of previously carbonated, ultramafic, oceanic lithosphere. Our observations are based on a recently discovered, exceptionally well-exposed, outcrop in northern Norway [4] containing frozen-in decarbonation reaction textures at the km scale. Our observations and textural analyses indicate breakdown of magnesium carbonate and serpentine to secondary olivine at depths shallower than 20 km. Secondary olivine is present as up to fist-sized nodules pseudomorphically replacing magnesite and as veins delineating escape pathways for the carbon-bearing aqueous fluid. We present first field observations and reaction textures and will discuss implications for the efficiency of carbon transport into the Earth’s mantle by subduction of carbonate-bearing oceanic lithosphere.

[1] Kerrick, D.M. & Connolly, J.A.D. (1998). Geology 26, 375-378.

[2] Dasgupta, R. & Hirschmann, M.M. (2010). EPSL 298, 1-13.

[3] Kelemen, P.B. & Manning, C.E. (2015). PNAS 112, E3997-E4006.

[4] Beinlich, A., Plümper, O., Hövelmann, J., Austrheim, H. & Jamtveit, B. (2012). Terra Nova 24, 446-455.
Fire susceptibility and transitional climate regime in Amazon tropics
Authors: Xu Xiyan , Jia Gensuo , Zhang Xiaoyan , Xue Ying
Published: March 2020

Amazon wildfire surge in 2019 once again raised the alarm about the fate of the Earth’s most biodiverse forest. Climate change and deforestation lead to greater vegetation water stress and susceptibility to fires. We use multiple satellite and climate reanalysis data to explore fire susceptibility in response to shifted climate regime due to global climate change and forest loss in Amazon regions. We found that climate in Amazon has been shifting to increased frequency of extreme conditions with increased drought extent and severity. The tropical vegetation that has adapted to its surrounding climate are less resilient under stress of climate change and highly susceptible to fire.  The fire susceptibility has been expanding through the transition season and northward to the tropical rain and seasonal forests. These results highlighted the links between fire risk, climate change and human activities in Amazon regions.
Carbon and Oxygen Isotope Fractionation of Pressurized CO2 as a Function of Temperature
Authors: Jacksier Tracey , Socki Rick
Published: March 2020

During liquid-vapor phase transition, CO2 can undergo isotopic fractionation in both C and O.  This phase transition can occur during routine cylinder handling, such as gas expansion or while subjecting the cylinder to cold temperatures without allowing the cylinders to come to thermal equilibrium prior to use. 

This work examines the isotope changes for both C and O in a series of controlled experiments on dual phase (liquid-vapor) and single-phase (vapor only) carbon dioxide contained in pressurized gas cylinders at sub-freezing, ambient and elevated temperatures.  The isotopic values were measured during the temperature equilibration from either cold or elevated temperatures to room temperature.  Isotopic values were observed to vary when the gas was at sub-freezing temperatures but not from elevated temperatures.  Stable isotope practitioners, who rely on pressurized carbon dioxide as a working IRMS laboratory reference gas, will find this work useful.
Land use/Land cover Changes and Associated Impacts on Water Yield Availability and Variation, Mereb-Gash River Basin in Horn of Africa
Authors: Measho Simon , Chen Baozhang , Pellikka Petri , Guo Lifeng , Zhang Huifang
Published: March 2020

Climate variability, drought, and deforestation are increasing in the Horn of Africa (HOA). Evaluating land use/land cover (LULC) changes and their impacts on water availability and variation are vital actions for regional land-use planning and water resources management. LULC changes during 2000-2015 were estimated using high resolution Landsat images and Google Earth Engine cloud platform, and land-use dynamics index (K). The impact of LULC change on water yield was evaluated using the InVEST model. The results at regional scale show that there were rapid decreases in the area of forests and barren lands (-K) while there was a drastic increase in built-up area (+K values). The transition was found to decrease from forested land to low biomass with highest and lowest values of 51.13% and 16.7%, respectively. There were similar LULC changes in the Mereb-Gash river basin. The total annual water yield increased for all the catchments during 2000-2015, and reached the peak in 2010. The highest annual water yield decreased in the forested lands from 43.18 million m3 in 2000 to 4.1 million m3 in 2015. There was a strong positive correlation between areal changes (%) and the annual water yield variations (%) in all the LULC types except for the water body, and the correlation was significantly positive for the forested areas (p<0.01). The study demonstrates that the decrease in forested areas and expansion in the built-up areas had large impact on water yield. The impacts may further increase pressure on the ecosystem services, exacerbate water scarcity, and food insecurity unless basic measures are planned and implemented.

Key words: LULC; climate variability; InVEST; annual water yield; K-index

 
Coupled hydrology - routing model to improve hydrogeological and hydraulic data across a tropical basin in Colombia
Authors: Arenas Maria , Arboleda Obando Pedro Felipe , Donado Garzón Leonardo David
Published: March 2020

Hydrologic models allow to simulate the water fluxes and storages inside a watershed, and so, to compute the water budget at different time and spatial scales. Even if they are important tools for water management, uncertainty can affect their results. The output data of the hydrologic model can be used to run other models, i.e, a hydrogeologic model (which needs recharge data) and hydrodynamic models (which need discharge data for some tributaries with no gauge stations). Therefore, with the scope to reduce uncertainty and to achieve a better representation in tropical basin systems, we focus on building a coupled hydrology model able to simulate data to be used inside of groundwater flow and surface water hydrodynamic models.  In order to do so, we decided to use Dynamic Topmodel, a recent development from the well – known Topmodel, as the hydrologic module, through the HRU (hydrological response units) approach to split the area in smaller units. Then, to include the routing processes, we decided to couple Dynamic Topmodel to the Variable Infiltration Capacity model 2D routing module (VIC-2D), to represent the drainage network using cells, and simulate discharge values at some non-gauged locations. The coupling was built under one single main hypothesis: all the cells inside a single HRU will produce the same recharge and runoff value. Based on this hypothesis we built the input data maps to run the routing module.

 

As our case study, we chose a 31 140 km2 basin in the Middle Magdalena Valley (MMV), a central area with important economic activities, as oil and gas (O&G) exploration and production, agriculture and livestock. Our model used cells of size 3 km with 76 HRU, but only seven parameter sets, so many of those 76 HRU shared parameter values, according to the digital elevation model (DEM), soil texture, and land used data. Our analysis is grounded on a record of 30 years of hydro-meteorological variables. The results of the coupling model described in a satisfactory way the following outcomes: (i) the fluxes among hydrosystems, (ii) channel flows, (iii) optimizing the computational performance (budget) of models in basins of tropical regions and (iv) allowing identification of trends on the discharge across the area to support the calibration of hydrodynamic models. In addition, the developed technique reduces the uncertainty of the model outcomes in areas with no data.
Evolution of mantle peridotite rocks - structures generated in a transition from the ductile-brittle regime in the Equatorial Atlantic
Authors: Barão Leonardo Mairink , Trzaskos Barbara , Angulo Rodolfo José , Souza Maria Cristina de
Published: March 2020

The exhumation of peridotite rocks in oceanic transform zones passes by the rheological transition between the ductile-brittle deformations until the complete emplacement in the oceanic lithosphere. São Pedro and São Paulo Archipelago, is located at 1° N latitude, 1000km from the Brazilian mainlad. Ten isles compose the archipelago with a total exposed area of 17 km². Those isles record the deformational products of ductile, brittle and the rocks/fluid interaction generating specific structures in each domain. The deformational stages are related to the transpressional and transtensional geodynamics of São Paulo Transform Fault (SPTF). The ductile-brittle fabrics were observed in a multiscale context, using drone images, geological mapping, fault analysis, and microstructural studies. Using all these tools to define the tectonic tensions and structures associated with a transition between ductile to the brittle deformational settings. Firstly during the transpressional context, the exhumation occurs associated with the ductile domain causing intense mylonitization in temperatures between 700° - 800°C. Leading to olivine and orthopyroxene recrystallization forming such as well-marked mylonitic foliation and rotated porphyroclast with left-lateral kinematic. The interaction with fluids initially originated from the mantle, generates fragmented crystals of amphibole and oxide-rich levels, marking the transition to semi-brittle deformation. The continuous and rapid uplift led to the superposition of deformation mechanisms, with reactivation of pre-existing structures and predominance of brittle deformation mechanisms. The tectonics associated with an NW-SE shortening in the transpressional tectonics context led to greater availability of hydrothermal fluids. Consequently, the formation of four serpentinization episodes, which are associated with semi-brittle to brittle transition, with temperatures between 300 - 400° C. The presence of serpentine marks the transition between semi-brittle to brittle regimes, whose dextral kinematics is marked by the domino faults, microfaults and gash veins. The kinematics at the brittle moment is compatible with the current movement of the SPTF. Finally, the complete exhumation and establishment of brittle mechanisms led to the carbonatation phase near the surface, with temperatures ranging from 150 - 300°C. The active NW-SE tectonic stress generated an E-W strike-slip faults that filled by carbonates, symbolizing the final exhumation stage.
Observation of the tailward electron flows commonly detected at the flow boundary of the earthward ion Bursty Bulk Flows in the magnetotail
Authors: Zhang Mao , Lu Quanming
Published: March 2020

By measurements of the Magnetospheric Multiscale (MMS) mission in the magnetotail from -24 to -15 RE , we identified 40 ion Bursty Bulk Flow events (BBFs) and investigated the electron behaviors during these BBFs. The ion flows peaked near the center of the plasma sheet and had a sharp flow boundary. The electron flow profile is distinct from the ion flows of the BBFs. Inside the BBFs, the strongest earthward electron flows are observed in the ion flow boundary, away from the current sheet center. Further away from the peak of the earthward electron flows, the tailward electron flows are observed in the edges of the ion flows, are mainly field-aligned with low energy, and are stronger than the earthward flows. It seems that the tailward low-energy electrons are energized at some places tailward of the spacecraft and then ejected towards Earth, consistent with the magnetic reconnection scenario in the magnetotail. The implication to the understanding of the astrophysical jets is suggested.
Possible dispersal routes based on individual-based modeling forced with past climate conditions.
Authors: Zeller Elke , Timmermann Axel
Published: March 2020

It has long been hypothesized that long and short term climate changes influenced early human evolution and dispersal. With the use of paleoclimate, archeological, genetic, and climate model data, we can infer climate factors that influenced dispersal and possible migration routes. Recent research has shown that with the use of data from these different disciplines, we can model human dispersal and interactions with the environment at a group level. However, decision-based questions such as push vs. pull scenarios and what is the optimal time to move are challenging to answer using classical differential-equation based models. With the use of individual-based modeling (IBM), we can connect archeological research with paleoclimate (modeling) data and build possible dispersal scenarios.

IBM has long been used in ecology to research the overall behavior of a group based on decisions made by individuals. In IBMs, each individual is modeled as a discrete agent who decides its action based on the environment and relation to other agents, thereby allowing for more individual variation and adaptation than is possible with classical differential-equation and difference-equation models.

Here we present some preliminary results from our climate forced IBM. Climate variables such as net primary production, temperature, and rainfall were obtained from a transient simulation of the LOVECLIM intermediate climate model. These climate factors were used for movement decisions and influence the birthrate and life span of the agents. We show the most likely dispersal routes for different climate scenarios and the role of dispersal strategies (push vs. pull).
Importance of Real-time PGV Shakemaps: Experience from 2018 ML 6.2 & 2019 ML 6.3 Hualien Earthquakes
Authors: Wu Yih-Min
Published: March 2020

Two earthquakes having almost the same magnitude and focal mechanism occurred in Hualien County, Taiwan, in 2018 and 2019. The 2018 earthquake had a magnitude  ML6.2 produced severe destruction; however, the 2019 earthquake ( ML=6.3) did not cause any significant damage. The P-Alert instrumentation network consisting of 711 instruments provided high-quality real-time peak ground acceleration (PGA) and peak ground velocity (PGV) shakemaps during both events. Considering recorded PGA, both events should cause substantial destruction. On the contrary, PGV shakemaps display a different pattern. The higher PGV values (more than 17 cm/s) are observed in the rupture zone during the 2018 earthquake (locations suffering building collapse) as compared to the 2019 earthquake, proving the fact that PGV is a better indicator of damage distribution. The PGV shakemap, currently only available for P-Alert network, provides crucial information that complements the PGA issued by the official agency in Taiwan
A Case Study of Snowstorm Associated with Jianghuai Cycle on Atmospheric Influence Factors and Character of Snow Cover
Authors: Yang Cheng fang
Published: March 2020

Abstract: This study investigates the character and complicated atmospheric influence factors of snow cover on a snowstorm event associated with Jianghuai cycle occurred from 21 to 22 February 2017 by automatic station, intensive and routine observation data. The results are as follows: (1) Special structure leads to different distribution  of snowfall and snow cover from south to north in Shandong province.(2) Snow depth rises to maximum when snow ends with timeliness. The maximum is not sure to continue at 8'clock next day.(3) Snow depth is influenced by precipitation type, snowfall, Snowfall intensity, air temperature, ground temperature and wind speed. Sleet can produce snow cover with 1cm before it converts to snow, or quantitative snow cover won't form. Snow-to-liquid ratio has great difference in various stations, and the average with 0.5cm·mm-1 in Shandong province is lower than in all country. Strong snowfall and snowfall intensive are favorable to form deep snow cover without melt snowfall, especially for air temperature and ground temperature higher than 0℃. More lower air temperature and ground temperature will benefit snow cover. The value of ground temperature threshold is about 0℃ when snow cover begin to form. The common character is that ground temperature drops quickly before visible snow cover and rises stably after 1 to 2 hours . Air temperature is usually below 0℃ when snow cover forms, or major snowfall will melt. Small wind speed is good for snow cover.
Key words: Jianghuai cycle, snowstorm, snow cover, influence factor
Occurrence of discontinuities in the ozone concentration data from three reanalyses
Authors: Krizan Peter
Published: March 2020

The aim of this presentation is to compare the occurrence of discontinuities in the ozone concentration data from the MERRA-2, ERA-5 and JRA-55 reanalyse, with the help of the Pettitt homogeneity test. We distinguish between the significant and insignificant discontinuities, according to the relation between the dispersion and the average ozone values before and after the discontinuity.    This occurrence is important for trend analyses, because the presence of discontinuities influences the values of trends and their significance. Discontinuities arise from the changing in the assimilation procedure, introducing new observation to the reanalyse, and changing of data quality. We search for their spatial, temporal and geographical occurrence. There are differences among these reanalyses. In the case of the MERRA-2 data, the transition from SBUV to EOS Aura data in 2004 has great impact on discontinuity behaviour. The frequent occurrence of discontinuities is seen in the uppermost model layers. The uppermost MERRA-2 layer is 0.1 hPa, while for ERA-5 this layer is 1 hPa. So there are differences in the vertical distribution of discontinuities among the reanalyses. The ozone data with the strong occurrence of the significant discontinuities is not suitable for trend analyses.   
The important role of mixing in scale interactions in the tropics and the coupled ocean/atmosphere system
Authors: Richards Kelvin , Natarov Andrei , Jia Yanli
Published: March 2020

Our focus is the way various scales of motion in the tropical ocean are linked through mixing and its modification by larger scales. Enhanced mixing caused by small vertical scale features (SVSs) in the equatorial thermocline is known to impact the state of the ocean and its interaction with the atmosphere, in particular the sea surface temperature of the Pacific cold tongue and ENSO variability. The SVSs are produced by wind variability (from, for instance, the MJO) and instabilities, with an equatorial enhancement caused by a combination of factors including the characteristics of the forcing and propagation of internal waves and near-equator inertial and sub-harmonic parametric instabilities. Numerous scale interactions are at play. For instance, an eastward extension of the warm(fresh) pool in the western tropical Pacific, typical under El Niño conditions, stratifies the upper ocean. This stratification can produce a dramatic decrease in the downward propagation of wind-generated inertia-gravity waves and a decrease in the mixing in the main thermocline. The associated changes to the thermocline are advected to the east and impact the eastern cold tongue and hence the coupling with the atmosphere. Using a combination of observations and models we investigate the properties of SVS activity, its impact on mixing, and interaction with larger scales. Of particular interest is the dependency on stratification, the spatial and temporal variability of wind forcing, the impact on larger scales, and the resolution of both observations and models. The good news is that with enough resolution the relevant scales can be captured in both observations and models.
Analysis of the Magmatic – Hydrothermal Volcanic Field of Tacora Volcano, Northern Chile, using Travel Time Tomography
Authors: Comte Diana , Pavez Claudia , Gutierrez Francisco , Gaytan Diego
Published: March 2020

Tacora Volcano (17º43’S – 69º46’W) is a composite stratovolcano that lies at the southernmost end of a 10 km-long volcanic lineament that extends between Chile and Perú. Around Tacora volcano, current thermal manifestations are two active fumarolic fields located at the western flank of the stratovolcano and at the volcano summit, indicating active magma degassing in a shallow hydrothermal system. Beneath Tacora volcano is located the NW Challaviento reverse fault that belongs to the Incapuquio - Challaviento fault system of Middle Eocene age. To complement previous exploration results and conceptual modeling developed by INFINERGEO SPA, seventeen short period seismic stations were installed around Tacora volcano, between August and December 2014. Using the P and S wave arrival times of locally recorded seismicity, a 3D velocity model was determined through a travel time tomography. According with the results, we interpreted high Vp /Vs values as water-saturated areas, corresponding to the recharge zone of Tacora hydrothermal system. In addition, low values of ΔVp/Vp (%) and Vp/Vs ratio represent the location of a gas-saturated magmatic reservoir between sea level and 2 km depth and circulation networks of magmatic-hydrothermal fluids. Low Vp/Vs volumes (magma reservoir / high temperature hydrothermal fluids), the presence of fumarolic fields and surface hydrothermal alteration have a spatial correlation. The above suggests a structural control of the Challaviento fault in the hydrothermal flow as well as a primary influence in the emplacement and location of the magmatic-hydrothermal reservoir. Finally, we present a cluster analysis using the ΔVp/Vp (%) parameter. Through this analysis, we found a method for the identification of a key structure in depth composed by the magma reservoir (low Vp/Vs ratios, low ΔVp/Vp (%)), clay level areas (intermediate values of ΔVp/Vp (%)), and degasification zones (low values of ΔVp/Vp (%)) directly related with the surface thermal manifestations.
Has the stratospheric HCl in the Northern Hemisphere been increasing since 2005
Authors: Han Yuanyuan , Tian Wenshou , Xie Fei
Published: March 2020

Stratospheric hydrogen chloride (HCl) is the main stratospheric reservoir of chlorine, deriving from the decomposition of chlorine-containing source gases. Its trend has been used as a metrics of ozone depletion or recovery. Using the latest satellite observations, the authors find that a significant increase of Northern Hemisphere stratospheric HCl during 2010–2011 can mislead trends of HCl in recent decades. Agree with previous studies, HCl increased from 2005 to 2011; while when removing the large increase of stratospheric HCl during 2010–2011, the increasing linear trend from 2005 to 2011 becomes weak and insignificant, in addition, the linear trend of Northern Hemisphere stratospheric HCl from 2005 to 2016 also shows weak and insignificant. The significant increase of HCl during 2010–2011 is attributed to a super strong north polar vortex and a reduced residual circulation during 2010–2011, which slowed down the transport of HCl from the low–mid latitudes to the high latitudes, leading to accumulation of HCl in the middle latitudes of the stratosphere during 2010–2011. Further analysis suggests that the strong polar vortex and the reduced residual circulation were caused by the joint effect of a La Niña event and the west phase of the quasi-biennial oscillation.
From Corinth gulf extension to Ionian subduction/collision (W. Greece): micro-seismicity survey to constrain local tectonics and regional geodynamics
Authors: Lefils Valentine , Rigo Alexis , Sokos Efthimios
Published: March 2020

The North-Eastern zone of the Gulf of Corinth in Greece is characterized by the rotation of a micro-plate in formation. The Island Akarnanian Block (IAB) have been progressively individualized since the Pleistocene (less than ~ 1.5 My ago). This micro-plate is the result of a larger-scale tectonic context with, on one side the N-S extension of the Gulf of Corinth to the East, and on the other side the Hellenic subduction to the South and the Apulian collision to the West. To the Northeast, the IAB micro-plate is bounded by a large North-South sinistral strike-slip fault system, the Katouna-Stamna Fault (KSF) and by several normal faults. To the North, normal faults reach the limit between Apulian and Eurasian plates and to the East, they form the East-West graben of Trichonis lake.

Although the structures and dynamics behind the Gulf of Corinth extension are today relatively known, nevertheless, the set of faults linking the Gulf of Corinth to the Western subduction structures remain poorly studied. The seismicity recorded by the Greek national network shows discrepancies regarding to the faults mapped on the surface.

At the end of 2015, a new micro-seismicity campaign started with the deployment of a temporary seismological network in an area ranging from the Gulf of Patras to the Amvrakikos Gulf toward the North. This network includes 17 seismic stations, recording continuously, added to the permanent stations of the Corinth Rift Laboratory (CRL) and of the Hellenic Unified Seismic Network (HUSN).

The analysis of the seismological records is still in process for the 2016 and 2017 years. Our study consists first in picking the P- and S- waves, and then to precisely localize the seismic events recorded by our temporary seismological network combined with the permanent ones. We will present here the event location map obtained for the 2016-2017 period, a new seismic velocity model, and focal mechanisms. The seismic activity including thousands of events, is characterized by the presence of numerous clusters of few days to few weeks duration. The clusters are analysed in detail by relative relocations in order to appraise their physical processes and their implications in the fault activity. We will discuss the deformation mode of the region and build a seismotectonic model consistent with the regional geodynamics and observations.
Towards spatial machine learning to reveal hidden patterns and relationships in national and international geochemical databases
Authors: Zhang Chaosheng
Published: March 2020

Environmental geochemistry is playing an increasingly important role in mineral exploration, environmental management, agricultural practices as well as links with health. With rapidly growing databases available at regional, national, and global scales, environmental geochemistry is facing the challenges in the “big data” era. One of the main challenges is to find out useful information hidden in a large volume of data, with the existence of spatial variation found at all the sizes of global, regional (in square kilometers), field (in square meters) and micro scales (in square centimeters). Meanwhile, the rapidly developing techniques in machine learning become useful tools for classification, identification of clusters/patterns, identification of relationships and prediction. This presentation demonstrates the potential uses of a few practical spatial machine learning techniques (spatial analyses) in environmental geochemistry: neighborhood statistics, hot spot analysis and geographically weighted regression.

 

Neighborhood (local) statistics are calculated using data within a neighborhood such as a moving window. In this way, spatial variation at the local level can be quantified and more details are revealed. Hot spot analysis techniques are capable of revealing hidden spatial patterns. The techniques of hot spot analysis including local index of spatial association (LISA) and Getis Ord Gi* are investigated using examples of geochemical databases in Ireland, China, the UK and the USA. The geographically weighted regression (GWR) explores the relationships between geochemical parameters and their influencing factors at the local level, which is effective in identifying the complex spatially varying relationships. Machine learning techniques are expected to play more important roles in environmental geochemistry. Challenges for more effective “data analytics” are currently emerging in the era of “big data”.

 
Improved Retrieval Methods for Sentinel-3 SAR Altimetry over Coastal and Open Ocean and recommendations for implementation: ESA SCOOP Project Results
Authors: Cotton David , Moreau Thomas , Roca Mònica , Gommenginger Christine , Cancet Mathilde , Fenoglio-Marc Luciana , Naeije Marc , Fernandes M Joana , Shaw Andrew , Restano Marco , Ambrosio Americo , Benveniste Jérôme
Published: March 2020

SCOOP (SAR Altimetry Coastal & Open Ocean Performance) is a project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, to characterise the expected performance of Sentinel-3 SRAL SAR mode altimeter products, and then to develop and evaluate enhancements to the baseline processing scheme in terms of improvements to ocean measurements. Another objective is to develop and evaluate an improved Wet Troposphere correction for Sentinel-3.

The SCOOP studies are based on two 2-year test data sets derived from CryoSat-2 FBR data, produced for 10 regions. The first Test Data Set was processed with algorithms equivalent to the Sentinel-3 baseline, and the second with algorithms expected to provide an improved performance.

We present results from the SCOOP project that demonstrate the excellent performance of SRAL at the coast in terms of measurement precision, with noise in Sea Surface Height 20Hz measurements of less than 5cm to within 5km of the coast.

We then report the development and testing of new processing approaches designed to improve performance, including, for L1B to L2:

Application of zero-padding

Application of intra-burst Hamming windowing

Exact beam forming in the azimuthal direction

Restriction of stack processing to within a specified range of look angles.

Along-track antenna compensation

 

And for L1B to L2

Application of alternative re-trackers for SAR and RDSAR.

 

Based on the results of this assessment, a second test data set was generated and we present an assessment of the performance of this second Test Data Set generated, and compare it to that of the original Test Data Set.

Regarding the WTC for Sentinel-3A, the correction from the on-board MWR has been assessed by means of comparison with independent data sets such as the GPM Microwave Imager (GMI), Jason-2, Jason-3 and Global Navigation Satellite Systems (GNSS) derived WTC at coastal stations. GNSS-derived path Delay Plus (GPD+) corrections have been derived for S3A. Results indicate good overall performance of S3A MWR and GPD+ WTC improvements over MWR-derived WTC, particularly in coastal and polar regions.

 

Based on the outcomes of this study we provide recommendations for improving SAR mode altimeter processing and priorities for future research.
Three-Dimensional Magnetic and Velocity Structures of Active Region 12673
Authors: Wang Haimin
Published: March 2020

We study the Solar Active Region (AR) 12673 in September 2017, which is the most flare productive AR in the solar cycle 24.  Observations from Goode Solar Telescope (GST) show the strong photospheric magnetic fields (nearly 6000 G) in polarity  inversion line (PIL) and apparent photospheric twist on September 6,  the day of X9.3 flare. Corresponding to the strong twist,   upflows are observed to last one day  at the center part of that section of PIL;  down flows are observed in two ends.  Transverse velocity fields are derived from flow tracking.   Both Non-Linear Force-Free Field (NLFFF) and Non-Force-Free Field (NFFF) extrapolations are carried out and compared to trace 3-D magnetic fields in corona. Combining with EOVSA, coronal magnetic fields between 1000 and 2000 gauss are found above the flaring PIL at the height range between 8 and 4Mm, outlining the structure of a fluxrope with sheared arcade.  The above magnetic and velocity fields, as well as thermal structure of corona, provide initial condition for further data-driven MHD simulation.