bluuebunny/crossref_metadata_2025 huggingface dataset:
Bio-GO-SHIP: Shifts in bacterial communities reveal subtle biogeochemical regimes across the Indian Ocean
Authors: Brock Melissa , Larkin Alyse , Martiny Adam
Published: March 2021

Historically, our understanding of ecological responses to biogeochemical gradients and physical dynamics in the Indian Ocean has been limited to regional studies. Microbial communities represent in-situ biosensors that are sensitive to changes in the surface ocean. They can therefore be used to identify where subtle changes in the environment occur and to understand links between the ecology and surrounding environment. Here, we perform the largest study of microbial biodiversity in the Indian Ocean, using 505 DNA samples collected on GO-SHIP cruises I07N and I09N. This dataset spans a large geographic area, starting in the southern Indian Ocean gyre, crossing through the equatorial zone, and entering the Arabian Sea or the Bay of Bengal. We used 16S rRNA amplicon sequencing to identify transition points in bacterial community structure and to define ecological boundaries. We found that these boundaries aligned with shifts in geochemistry (e.g., nutrient availability) and/or physical dynamics (e.g., ocean fronts, eddies, and salinity), indicating fine-scale regional separation in biogeochemical functioning. Thus, our study demonstrates how using microbial communities provides an integrated approach for evaluating links between the ecology, geochemistry, and physical dynamics of the Indian Ocean.
Stratigraphy, geochemistry, and petrology of the Upper Cretaceous volcanic arc sequence north of Istanbul, Pontides, NW Turkey
Authors: Ay Cemre , Sunal Gürsel , Okay Aral I.
Published: March 2021

Upper Cretaceous arc-related volcanic and volcanoclastic units overlying the Paleozoic sedimentary rocks of the Istanbul Zone are a key unit related to the opening of the Black Sea as a back-arc basin. They formed as a result of north dipping subduction of the Neo-Tethys Ocean beneath Laurasia. We studied the Upper Cretaceous volcanic units north of Istanbul along several stratigraphic sections, and present new geochemical data from the volcanic rocks in order to understand Cretaceous geodynamic evolution of the İstanbul Zone.

The Upper Cretaceous  volcanic units north of Istanbul are divided into two formations. At the base there is a fore-arc turbidite succession,the İshaklı Formation, which is made up of volcaniclastic sandstone, shale, marl, tuff, debris flow horizons and epiclastic rocks of Turonian age. The İshaklı Formation is conformably overlain by the volcanoclastics,  tuffs, andesite and basalt lavas and agglomerates- the Riva Formation, which represents the arc/ intra-arc series.

Geochemically, basalts and basaltic andesites of the Riva Formation are low K calc-alkaline to medium-high K calc-alkaline and with magnesium numbers ranging from 32.6% to 51.5% Primitive mantle normalized spider diagram of trace elements show  enrichment in LILE elements (K, Rb, Sr, Cs, Ba, Th and U) and depletion in HFS elements ( Nb,Ta and Ti) . The high ratio of LILE/ HFS and negative Nb-Ta anomalies indicate that the volcanism evolved in subduction setting. Chondirite-normalized REE pattern display slight negative Eu anomalies and the La/Yb ratios of the samples range between 2,76 and 4,89. Our new geochemical, stratigraphical and the regional geological data suggest that north of Istanbul there was a transition from fore-arc deposition to arc volcanism during the Late Cretaceous opening of the Western Black Sea.  Considering the whole Pontide – Sredna-Gora Upper Cretaceous magmatic arc, it can be stated that calc-alkaline volcanism developed in relation to northward subduction of the Neo-Tethys oceanic lithosphere during the Turonian, and may have passed into high-K calc alkaline and shoshonitic magmatism as a result of the progressive extentional tectonism during the Campanian.
A new methodological proposal for improving flood risk mapping using geostatistical techniques in Central-Western Spain
Authors: Guardiola-Albert Carolina , Garrote-Revilla Julio , González-Jiménez Miguel , Díez-Herrero Andrés
Published: March 2021

The bathymetry of the riverbed is essential in flood risk assessment at large rivers, and yet its acquisition is a slow process and endowed with a high budget economic. Moreover, recent research works have shown the importance of improving the geometrical characterization inside the riverbed, which is an issue due to the inability of light to penetrate water bodies. So, most of LiDAR techniques allow us for high resolution surface topography data but not for water occupied river channels. This, apart from making these jobs more difficult, sometimes generates the renouncement of it, using the topography of the water sheet as a riverbed, or the simplification of river channel configuration (trapezoidal transversal sections) which frequently generate an overestimation of flood zones. To overcome these deficiencies, a novel methodological approach has been developed to simulate this bathymetry using simplified models. The proposed approach is based upon the calibration of the flow roughness parameters (Manning´s n value) inside the riverbed. The use of abnormally low Manning´s n values has made it possible to reproduce both the extent of the flooded area and the water depth value within it in an acceptable manner: first results from hydrodynamic modelling of 500-year return period peak flow show the reduction of the water depth average error from 50-75 cm to only about 10 cm; and a direct economic flood damage differences reduction from 25-30% to values of about 5%.

The present work proposes to go further with these investigations and perform a robust geostatistical analysis of hydrodynamic modelling outputs obtained with modified Manning’s n values. The methodology scheme is to characterize the spatial distribution of the results and its spatial correlation with other variables, as the distance to the riverbank or flow rates (for different return periods), through variogram models. This quantitative statistical description of the floodable areas, depending on the Manning’s n value model used and the return period considered, could be used to perform geostatistical simulations that allow to quantify the spatial uncertainties associated to the studied models; as well as to calibrate the optimal spatial distribution of modified Manning’s n values inside the riverbed. These findings will be analysed as guidelines to construct more robust and reliable flood risk estimations; and can be applied to many other study cases around the world, saving analysis time and execution costs, but without losing its scientific rigour.
Advancing carbon cycle projections with stomatal optimality models linked to plant hydraulics
Authors: Anderegg William , Kerr Kelly , Sperry John , Todd Henry , Trugman Anna , Venturas Martin , Wang Yujie , Zenes Nicole
Published: March 2021

Optimal stomatal control models have shown great potential in predicting stomatal behavior and improving carbon cycle modeling. Basic stomatal optimality theory posits that stomatal regulation maximizes the carbon gain relative to a penalty of stomatal opening. Many optimization models take a similar approach to calculate instantaneous carbon gain from stomatal opening. But stomatal optimization models often diverge in how they calculate the corresponding penalty of stomatal opening. We will present our recent work on this penalty function, the conditions that influence the penalty function, and compare and evaluate 10 different optimization models in how they quantify the penalty and how well they predict stomatal responses to the environment. We quantitatively tested different models against multiple leaf gas-exchange datasets. The optimization models with better predictive skills have penalty functions that meet seven key criteria and use fitting parameters that are both few in number and physiology based. The most skilled models are those with a penalty function based on stress-induced hydraulic damage. We conclude by examining the key uncertainties in these optimization models for improving predictions of carbon and water fluxes, as well as demographic rates like drought-induced tree mortality.
Investigating the connection between tropospheric blocking and sudden stratospheric warming events using GNSS radio occultation observations
Authors: Yessimbet Kamilya , Steiner Andrea
Published: March 2021

Both sudden stratospheric warming (SSW) events and tropospheric blocking events can have a significant influence on winter extratropical surface weather. Upward propagating planetary waves from the troposphere can interact with the stratospheric mean flow and disrupt the stratospheric polar vortex, which is associated with an SSW event. Blocking has often been suggested as one of the tropospheric precursors for anomalous upward propagating wave activity flux. It remains an open question to what extent upward wave activity caused by blocking is related to SSW events. In the present study, we examine the evolution of the Eliassen-Palm fluxes during blocking events that precede SSWs. We use Global Navigation Satellite System radio occultation measurements for this analysis to provide accurate and vertically well-resolved information on the wave coupling between these two phenomena in the upper troposphere and stratosphere. First results will be presented and discussed.

Keywords: sudden stratospheric warming, Eliassen-Palm flux, blocking
The Late-Quaternary morphostratigraphic record of glaciation, paleoseismicity and postglacial environmental changes in fjord-lakes of Québec-Labrador 
Authors: Lajeunesse Patrick , Trottier Annie-Pier , Gagnon-Poiré Antoine , Normandeau Alexandre , Brouard Etienne , Morissette Antoine , Philibert Geneviève
Published: March 2021

Hydroacoustic surveys were conducted in eight fjord-lakes of Québec-Labrador in order to analyse their Late-Quaternary geomorphological and stratigraphic record of glaciation, paleoseismicity and postglacial environmental changes. This large morphostratigraphic dataset provided a unique opportunity to establish a conceptual model of the evolution for fjord-lakes in relation to deglaciation, glacio-isostatic rebound, sediment fluxes and paleoseismicity. The analysis of the morphology and distribution of many morainic deposits into the fjord-lakes (hummocky moraines, morainic sills and morainic complexes) allows relating their formation to the glacial erosion potential, as well as to climatic and topographic controls. During past glaciations, a topographic sill was left uneroded at the opening of valleys due to the decrease in the glacial erosion potential associated with the lateral extension of the glacier down-ice; this bedrock sill created in turn an anchoring point to the ice during deglaciation. Hummocky moraines were documented at the outlet of five fjord-lakes that are located within the deepest and narrowest valleys of the studied systems. Based on our analysis of these sublacustrine landform-sediment assemblages, fjord-lakes constitute distinct sedimentary systems that should be differentiated from typical fjord system (i.e., in marine waters). The large-scale landforms contained in the fjord-lakes of Québec-Labrador (i.e., esker, moraines, gullies, lateral banks, turbidity channels and circular cavities) are inherited from their past subglacial, glaciomarine and paraglacial conditions, while only small deltaic bedforms (i.e., sediment waves and crescent-shaped bedforms) were formed in postglacial times. The present-day hydrological regime of fjord-lakes of Québec-Labrador is considered river-driven, except for the lakes located near active seismic zones where widespread postglacial mass-movements are documented.
A hierarchical approach linking hydraulic and ecological modeling for habitat predictions for riverine pioneer vegetation
Authors: Fink Sabine , van Rooijen Erik , Vanzo Davide , Vetsch David F. , Siviglia Annunziato , Scheidegger Christoph
Published: March 2021

The distribution of sessile riparian plant species and their habitats along riverways are highly dependent on river dynamics and connectivity. River restoration and conservation of riparian plant species rely on expert knowledge and more recently also on modelling approaches to predict species’ occurrence. Ecological modelling on habitat suitability for terrestrial species is usually based on climatic and topographic features, whilst river hydrodynamics is rarely considered.

Our study aims at predicting suitable habitat for a characteristic pioneer species for dynamic riverine habitats, the German Tamarisk (Myricaria germanica). Habitat predictions are tested in a case study on a floodplain along Moesa river in canton Grisons in South-East Switzerland. We link two modeling approaches having two different spatial scales using a hierarchical process. First, we define a large-scale habitat suitability matrix based on climatic, geological and topographic predictors. Using a two-dimensional hydrodynamic model, inundation frequency maps and flood level maps for several significant months for German Tamarisk establishment are constructed, to further refine the niche for the riparian plant.

The predicted habitat suitability is evaluated with species presence data for both adult and offspring plants. Our results allow gaining insights into the importance of linking ecological and hydraulic models having different spatial and temporal scales, for more refined predictions of riparian species distribution.
Monitoring changes in salinity and sodicity in a tile-drained field in the B-XII irrigation district (SW Spain) using electromagnetic induction sensing and inversion.
Authors: Gómez Flores José Luis , Ramos Rodriguez Mario , González Jiménez Alfonso , Farzamian Mohammad , Herencia Galán Juan Francisco , Salvatierra Bellido Benito , Cermeño Sacristán Pedro , Vanderlinden Karl
Published: March 2021

Continuous monitoring of soil salinity/sodicity is of prime importance in environments such as the B-XII irrigation district (SW Spain) where a shallow saline water table and intensive irrigated agriculture create a fragile equilibrium between salt accumulation and leaching in the topsoil. We evaluate to which extend electromagnetic induction (EMI) sensing and inversion with limited calibration can be used to accomplish such monitoring purposes, given that widespread soil sampling and laboratory analyses are prohibitive for economic and technical reasons.

Detailed EMI surveys were performed in 2017 and 2020 in a 4-ha tile-drained field with a heavy clay soil. Soil samples were taken at different locations and depths along a transect and analyzed for salinity/sodicity-related parameters. Inversion of the EMI signals along the investigated transect yielded consistent conductivity images for both years and showed a strong relation (R2<0.95) with saturated paste extract conductivity. The observed spatial conductivity patterns persisted from 2017 to 2020, although the obtained absolute values of the salinity/sodicity parameters changed slightly. This indicates that salinity hotspots persist in time and are mainly associated with wet locations, where salt movement towards the topsoil is promoted, possibly as a result of deficiencies in the performance of the drainage system.

Our results show that inversion of EMI signals offers a powerful means for accurately monitoring spatial and temporal changing salinity/sodicity under the specific conditions of the B-XII irrigation district.

 

Acknowledgement

This work is funded by the Spanish State Agency for Research through grant PID2019-104136RR-C21 and by IFAPA/FEDER through grant AVA2019.018.

 
Artful-Geoscience: Co-Creating Urban Subsurface Futures? A discussion and an invitation. 
Authors: Hawkins Harriet , Bricker Stephanie , Cotteril Carol , Dunnet Eilidh , Hicks Anna , Napier Hazel
Published: March 2021

The urban subsurface is key to developing sustainable urban futures (SDG 11). Yet, as is well acknowledged, geoscientists face many challenges in engaging stakeholders and communities with the urban subsurface, as well as the challenges associated wtih fragmented data sources, knowledge gaps, citizen ‘oversight,’ and challenging subsurface cultural associations (Bricker et al. 2017, 2019). In this paper we present a case for the value of the intersections between geoscience and creative practices (from visual methods to participatory arts) in helping to address some of these challenges. To make our case we present preliminary findings from a collaboration between geoscientists and science communicators based at the British Geological Survey, and a cultural geographer experienced in researching and creating art-science collaborations. We explore three things:

We close our discussion with an invitation to join us in forming a network exploring the potential of art-geoscience collaborations for understanding, using and preserving the urban subsurface. 
How do the surface energy fluxes change when a more realistic land cover is included in the WRF model? An evaluation using BLLAST data
Authors: Román-Cascón Carlos , Lothon Marie , Lohou Fabienne , Hartogensis Oscar , Vila-Guerau de Arellano Jordi , Pino David , Yagüe Carlos , Pardyjak Eric
Published: March 2021

Ideally, numerical weather prediction (NWP) and climate models should include a proper representation of the land surface to correctly simulate the surface energy fluxes and, ultimately, provide successful forecasts of atmospheric variables of common interest for the humans (2-m temperature, 10-m wind speed, relative humidity, etc.). However, in some cases, the issues begin in the first link of this chain, i.e., the surface characteristics included in the model do not represent appropriately the real surface ones in certain areas.

This work investigates how the simulated surface energy fluxes change when the land cover (LC) of an area is improved using a more realistic and higher-resolution dataset. We evaluate the Weather Research and Forecasting (WRF) model simulating a fair-weather day in a heterogeneous area of southern France. Firstly, we use the default LC database in WRF, which differed significantly from the real LC in the area. Secondly, we improve the LC representation of the studied area using a more realistic 1-km dataset prepared by the CESBIO research laboratory. The simulated fluxes were evaluated in a 19x19 km area with gridded area-averaged fluxes computed using measurements from five eddy-covariance towers deployed over different vegetation types during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign. The evaluation is done using four land-surface models (LSM) available in WRF (Noah, Noah-MP, CLM4 and RUC).

The results differed depending on the LSM and displayed a high dependency of the simulated fluxes on the specific LC definition within each grid cell. The simulated fluxes improved when a more realistic LC dataset is used except for some LSMs that considered extreme surface parameters for some LC categories (coniferous forest and urban surfaces). Therefore, our findings encourage to check (and improve if needed) the surface representation in the model over the area of analysis, as well as to update surface parameters for some vegetation types.
Implementation of geostatistical models for large spatiotemporal datasets using multi-resolution approximations
Authors: Appel Marius , Pebesma Edzer
Published: March 2021

The multi-resolution approximation approach (MRA) [1] provides an efficient representation of Gaussian processes that scales beyond millions of observations. MRA leaves flexibility in the selection of covariance functions and allows to trade off computation time against prediction performance, depending on the selection of parameters. Recent work [2] has shown how MRA can be used for global spatiotemporal processes by integrating nonstationary covariance functions, where parameters vary over space and/or time following a kernel convolution approach. As such, MRA turns out to be a promising approach for geostatistical modelling of global spatiotemporal datasets, such as those coming from Earth observation satellites.

In this work, we show how MRA can be used for spatiotemporal analysis from a practical perspective. In the first part, we will discuss the influence of parameters (spatiotemporal shape of partitioning regions, the number of basis functions, and the number of partitioning levels) by analyzing a real world dataset. In the second part, we will present and discuss our implementation as an R package stmra[3]. We will demonstrate how traditional models as from the gstat package can be implemented efficiently with MRA, and how non-stationary models can be defined by users in a relatively simple way. 

[1] Katzfuss, M. (2017). A multi-resolution approximation for massive spatial datasets. Journal of the American Statistical Association, 112(517), 201-214

[2] Appel, M., & Pebesma, E. (2020). Spatiotemporal multi-resolution approximations for analyzing global environmental data. Spatial Statistics, 38, 100465.

[3] https://github.com/appelmar/stmra
Temperate-zone reforestation as a tool for local climate adaptation? 
Authors: Novick Kimberly
Published: March 2021

In addition to dramatic reductions to anthropogenic greenhouse gas emissions, most pathways for limiting global warming to less than 2 degrees C rely on managed alterations to the land surface designed to increase land carbon uptake and storage (so-called “natural climate solutions”, or NCS). Reforestation is the NCS with the largest estimated climate mitigation potential, and at least in energy-limited temperate climates, evidence is mounting that transitions from short-stature ecosystems (croplands, grasslands) to forests substantially reduce surface temperature. In this way, reforestation, at least in some places, may also represent a useful tool for local climate adaptation. However, existing work on the topic has tended to focus on how reforestation affects mean annual and seasonal surface temperature, with comparatively less attention paid to the biophysical impacts of reforestation when local cooling would be most beneficial (i.e. at mid-day, and especially droughts and heat waves). Moreover, while surface temperature is a critical driver of ecosystem processes, arguably the near-surface air temperature is the more relevant target for climate adaptation. The duality between reforestation impacts on surface and air temperature has historically been challenging to deconvolve, and thus we do not yet understand the extent to which forest surface cooling extends to the air. In this talk, new strategies are discussed for blending flux tower data and remote sensing observations to uncover the links between reforestation, surface energy balance, and near-surface air temperature dynamics, with a particular emphasis on how plant water use strategies mediate these relationships during summer days and periods of hydrologic stress.  
Developing resilience to hydrologic extremes in irrigated agriculture through risk transfer mechanisms in the context of southeastern Brazil
Authors: Benso Marcos Roberto , Gesualdo Gabriela Chiquito , Mendiondo Eduardo Mario , Ribbe Lars , Nauditt Alexandra
Published: March 2021

In the last decades, we have witnessed increasing losses on crop yield due to an increase in magnitude and frequency of hydrological extremes such as droughts and floods. These hazards promote systematic and regressive impacts on the economy and human behavior. Risk transfer mechanisms are key to cope with the economic impacts of these events, therefore safeguarding income to farmers and building resilience to the overall sector. The index-based insurance establishes an index that can be monitored in real or near-real-time, which is associated with losses to a specific agent. While the manifestation of the causality hazard to exposure and exposure to damage and its mathematical representation in cash flow equations is a hard task, incorporating an objective and transparent index adds up a new challenge to this modeling framework. Moreover, past events that have been used as the main guide to evaluating expected losses given risk can no longer offer an accurate risk estimation due to environmental changes. This work aims to tackle the hydrologic extremes risk transfer modeling in irrigated agriculture to obtain optimized premium values and parameters of an insurance fund for irrigated agriculture in Southeastern Brazil. This study will be developed in the Piracicaba, Jundiaí, and Capivari river basin, also known as PCJ catchment in the states of São Paulo and Minas Gerais, Brazil. The region, with approximately 5 million inhabitants, is considered one of the most important in Brazil due to its economic development, which represents about 7% of the National Gross Domestic Product (GDP). The Hydrologic Risk Transfer Model of the Hydraulic and Sanitation department of the University of São Paulo (MTRH-SHS) will be used to obtain optimized premium values. The main index variable is streamflow fitted to extreme value theory distribution for low and high flows. To evaluate climate change and land-use change scenarios, Regional Climate Models (RCMs) and land use projections will be related to streamflow in a hierarchical Bayesian framework. Synthetic data will be then simulated according to scenarios previously defined in a Monte Carlo approach. The hazard-damage function will be obtained by total crop yield and revenue per municipality, then the relationship between the index and expected losses is determined in an empirical equation. Finally, a cash flow computation is run with synthetic data obtaining optimized premiums in a way to minimize fund storage values. We expect to provide further evidence of the feasibility of actuarially fair premium values for the agents in the sector considering global phenomena of climate change and land-use change. Results will support climate change adaptation plans and policy as well as contribute to methods for estimating risk in a changing environment.
Advantages of calibrating a daily rainfall-runoff model to monthly streamflow data
Authors: Lerat Julien , Thyer Mark , McInerney David , Kavetski Dmitri
Published: March 2021

Development of robust approaches for calibrating daily rainfall-runoff models to monthly streamflow data enable modelling platforms that operate at daily time step to be applied in practical situations. Here precipitation is available at the daily scale, but observed streamflow is available only at the monthly scale (e.g. predicting inflows into large dams). This study compares the performance of the daily GR4J hydrological model when calibrated against (1) daily and (2) monthly streamflow data. The performance comparison relies on a wide range of metrics and is undertaken for 508 Australian catchments. Two evaluation periods (1975–1992 and 1992–2015) and four objective functions (including sum-of-squared-errors of Box-Cox transformed streamflow and the Kling-Gupta efficiency) were tested.

Monthly calibration performs similar to or better than daily calibration in most sites and both periods in terms of bias and fit of the flow duration curve. This result remains the same when the flow duration curve is computed at the daily time step, which constitutes a significant finding of this study.

However, the performance of monthly calibration is worse than daily calibration for daily pattern metrics such as Nash-Sutcliffe efficiency in most sites and both periods. Significant improvement can be achieved if the flow-timing parameter of GR4J is regionalised, effectively reducing the number of calibrated parameters. Similar results are obtained for other pattern metrics and all objective functions.

These findings suggest that monthly calibration of rainfall-runoff models using daily-rainfall and monthly-streamflow data is a viable alternative to daily calibration when no daily streamflow data are available.
Detecting anthropogenic effects on the record-warm northwestern Pacific sea surface temperature in August 2020
Authors: Hayashi Michiya , Shiogama Hideo , Emori Seita , Ogura Tomoo , Hirota Nagio
Published: March 2021

August 2020 set a new record high sea surface temperature (SST) in the northwestern Pacific (NWPac; 120°E–180°E, 20°N–35°N). This anomalous condition potentially intensified tropical cyclones such as Typhoon Haishen, causing severe damage to the Korean Peninsula and Japan. Although the NWPac Ocean has gradually warmed due to human-induced greenhouse gas emissions since the mid‐20th century, the extent to which anthropogenic climate changes increase the occurrence likelihood of such regionally unprecedented warm SSTs is unclear yet. Here we analyzed the historical and SSP2-4.5 scenario simulations of CMIP6 and DAMIP as well as observational datasets. Our results show that owing to historical anthropogenic forcing, the occurrence probability of the 2020 record-warm NWPac SST is increased from once-in-1000 years to about once-in-15 years in 2001-2020. As warming caused by greenhouse gases was largely canceled by aerosol cooling, anthropogenic effects on the NWPac SST were not distinguishable from internal variability in the 20th century. The SSP2-4.5 scenario simulations also indicate that the 2020 record-warm SST is becoming a new normal climate condition of August by 2031–2050, or once the global air temperature above preindustrial level exceeds 1.5°C.
Development of in situ measurement of solid-state deformation in a large anvil press utilizing a piezoelectric crystal
Authors: Dolinschi Jonathan , Frost Dan
Published: March 2021

In situ measurement of solid-state deformation in a large volume press has historically required use of neutron and x-ray scattering facilities. The lack of widespread availability of these facilities has limited the abilities of researchers to measure in situ deformations on a regular basis. We have developed an assembly that utilizes a piezoelectric crystal within a typical large volume press assembly in a 6-axis press at pressures up to 5 GPa. The basic design of the assembly can be applied to multiple assembly sizes for a wide range of possible pressures. The piezoelectric crystal is a round disk, <1 mm in diameter, that is sputter coated with Au. Copper wires are placed through drilled holes in the side of the assembly, one connected to each side of the disk. The crystal generates a voltage across the two faces when a deviatoric stress is applied that is measured and plotted in real-time during the experiments. The voltage is then used to calculate strain and strain-rate in uniaxial compression. Using the known equation of state of the piezoelectric crystal, such as quartz or gallium orthophosphate, the stresses responsible for the strain can be calculated. Thus, we can measure the stress and strain regime of simple deformation within an assembly in situ in real-time during the deformation. We have measured strain-rates as low as 10-7 s-1 over a greater than 30-minute timescale. The total strain on the assembly can be measured by the total distance advanced by the press piston, which must be accommodated. Comparing the differences in strain accommodated by the piezoelectric crystal between separate experiments allows us to infer the strain accommodated by the sample under investigation.

Current limitations in measuring lower strain-rates are charge-leakage around the piezoelectric crystal causing a voltage drift during measurements and limitations in high-temperature experiments due to phase transitions during heating in the piezoelectric crystals to phases that are not piezoelectric. Future work will concentrate on finding a suitable, high-resistance material to place around the piezoelectric crystal to limit charge leakage and designing the assembly such that the piezoelectric crystal experiences lower temperature during heating than the sample to avoid phase transitions in the crystal.
Antarctic Sedimentary Basins: defining crucial constraints on ice-sheet and solid-earth dynamic interactions
Authors: Aitken Alan , Li Lu , Kulessa Bernd , Jordan Thomas , Whittaker Joanne , Anandakrishnan Sridhar , Greenbaum Jamin , Schroeder Dustin , Whitehouse Philippa , Eisen Olaf , Siegert Martin
Published: March 2021

Subglacial and ice-sheet marginal sedimentary basins have very different physical properties to crystalline bedrock and, therefore, form distinct conditions that influence the flow of ice above. Sedimentary rocks are particularly soft and erodible, and therefore capable of sustaining layers of subglacial till that may deform to facilitate fast ice flow downstream. Furthermore, sedimentary rocks are relatively permeable and thus allow for enhanced fluid flux, with associated impacts on ice-sheet dynamics, including feedbacks with subglacial hydrologic systems and transport of heat to the ice-sheet bed. Despite the importance for ice-sheet dynamics there is, at present, no comprehensive record of sedimentary basins in the Antarctic continent, limiting our capacity to investigate these influences. Here we develop the first version of an Antarctic-wide spatial database of sedimentary basins, their geometries and physical attributes. We emphasise the definition of in-situ and undeformed basins that retain their primary characteristics, including relative weakness and high permeability, and therefore are more likely to influence ice sheet dynamics. We define the likely extents and nature of sedimentary basins, considering a range of geological and geophysical data, including: outcrop observations, gravity and magnetic data, radio-echo sounding data and passive and active-source seismic data. Our interpretation also involves derivative products from these data, including analyses guided by machine learning. The database includes for each basin its defining characteristics in the source datasets, and interpreted information on likely basin age, sedimentary thickness, surface morphology and tectonic type. The database is constructed in ESRI geodatabase format and is suitable for incorporation in multifaceted data-interpretation and modelling procedures. It can be readily updated given new information. We define extensive basins in both East and West Antarctica, including major regions in the Ross and Weddell Sea embayments and the Amundsen Sea region of West Antarctica, and the Wilkes, Aurora and Recovery subglacial basins of East Antarctica. The compilation includes smaller basins within crystalline-bedrock dominated areas such as the Transantarctic Mountains, the Antarctic Peninsula and Dronning Maud Land. The distribution of sedimentary basins reveals the combined influence of the tectonic and glacial history of Antarctica on the current and future configuration of the Antarctic Ice Sheet and highlights areas in which the presence of dynamically-evolving subglacial till layers and the exchange of groundwater and heat with the ice sheet bed  are more likely, contributing to dynamic behaviour of the Antarctic Ice Sheet.  
Formation of Cyprus Lows within Red-Sea Trough
Authors: Etkin Adi , Ziv Baruch , Saaroni Hadas , Harpaz Tzvi
Published: March 2021

The Red-Sea Trough (RST) is a lower-level trough extending from the tropical low-pressure to the Levant. Its annual occurrence is 20%, between October and May, producing mostly dry weather, but occasionally active and causing local showers and floods. During winter the dominant synoptic system over the Levant is the Cyprus low (CL). Previous studies showed that some CLs form within pre-existing RSTs, through a tropical-extratropical interaction.

This study is the first comprehensive climatological framework of such formation events, analyzing occurrence, seasonality and the resulting rainfall in Israel. The study looked at events of new CLs formed within the domain 31°-35°N, 30°-36°E while a RST was detected within 24 hours before the event. We used the 6-hourly ERA-Interim database, with 0.75°×0.75° resolution, during 1979-2017, and identified 104 formation events, which constitute 10% of the CLs. Most events occurred during fall and early winter, as the case for the RST. Eighty-four percent of them formed during the evening or the night, and almost two thirds of the CLs disappeared temporarily at noon and regenerated afterwards. This is attributed to the sea/land diurnal oscillation. Most of the CLs that formed were found shallow with little rain, but occasionally became major storms, like "Alexa", which caused extreme snowing in Jerusalem, in December 2013.

The evolution scenarios leading to formation events were divided into four clusters, according to the synoptic situation at the 500-hPa geopotential height. The first one is characterized by a closed cyclone approaching from the southwest, often connected to active RSTs, such as the event that occurred in 2-4 November 1994. In the second, a trough is deepening from the northern sector, possibly a polar intrusion, like the "Alexa" storm. In the third, the most populated cluster, a trough is approaching from the west. A separate cluster contains four events with no upper-level support.
Research on the single-host parallel computing with the local time step scheme for modeling of hydro-sediment-morphodynamic processes
Authors: Zhao Zixiong , Hu Peng , Li Wei , Cao Zhixian , He Zhiguo
Published: March 2021

In recent decades, computational hydraulics and sediment modelling have a great development due to compute technology. Applying a finite-volume Godunov-type hydrodynamic shallow water model with hydro-sediment-morphodynamic processes, this work demonstrates and analysis the ability of single-host parallel computing technology with algorithmic acceleration technology. This model is implemented for high-performance computing using the NVIDIA’s Compute Unified Device Architecture (CUDA) programming framework, using a domain decomposition technique and across multiple cores through an efficient implementation of the Open Multi-Processing (Open MP) architecture, and using an algorithmic acceleration technology named local time stepping scheme (LTS), which is capable of obtain much efficiency improvement via different time step sizes for different grid sizes. The model is applied for three cases, through which we compare the effectiveness of CPU, Open MP, Open MP+LTS, CUDA, and CUDA+LTS, demonstrating high computational performance across CUDA+LTS which can lead to speedups of 40 times with respect to CPU and high-precision results across CUDA +LTS.

KEY WORDS: Hydro-sediment-morphological modeling; local time step; Open MP; CUDA.
Simulation Study of the Wind Dynamics over Mont Tai during the Transition Periods
Authors: Tsai Iheng , Zhang Meigen
Published: March 2021

Tai-An city located near the southern foothill of Mont Tai (117.105 °E, 36.256 °N, 1526 m a.s.l.) is known for severe ozone air pollution, frequent nocturnal surface ozone enhancement events, and especially the non-negligible contribution of ozone region transport, owing to diurnal thermally driven circulations induced by steep conical isolated topography. Therefore, In this study, mesoscale wind and temperature structure around Mont Tai region in summer 2018 is predicted by the Regional Atmospheric Modeling System (RAMS). After rigorous model validation, viz. the De Ridder's interpolation technique within the roughness sublayer and the statistical performance metrics, objectively ensuring the credibility of the simulation results, the a priori selection of Valley-wind days identifies are expected to be dominated by the thermally driven flow. We focus on the wind dynamic in the morning and evening transition periods on the valley-wind days. RAMS model not only reproduced the temporal sequence of the flow reversal between different above-ground heights, various local aspects and upstream/downstream positions but also captured the majority of energy transfer mechanisms during transition periods. Besides, we developed the code simulation of direct shortwave radiation included the topographic shadowing effect to repair RAMS missing module.
Detecting evapotranspiration biases in reanalyses and regional climate modeling
Authors: Dan Jingyu , Gao Yanhong
Published: March 2021

As the highest plateau in the world, the Tibetan Plateau (TP) exerts great impacts on regional and global climate and water cycle through interactions between land and free atmosphere. Terrestrial evapotranspiration is a critical component of the Earth's water cycle. To better understand the heterogeneity of the evapotranspiration over the Tibetan Plateau and its influences, we conducted a whole year dynamical downscale modelling (DDM) with the horizontal resolution at 28km and a convection permitting modelling (CPM) at 4km for 2014. DDM and CPM simulation results are compared with an satellite retrieving dataset, which is referred as OBS in the following, the global land surface data assimilation system (GLDAS) and two commonly used reanalyses ERA-Interim and ERA5, as well. The annual and seasonal means and seasonal variabilities are inter-compared. The evapotranspiration over ten dominant land use types are investigated based on six datasets. Differences with the satellite dataset are illustrated and relationships with soil moisture and temperature, precipitation and radiation are explored. The followings are obtained. GLDAS generally reproduces magnitude and pattern of the OBS; reanalyses overestimate, DDM and CPM underestimate compared to the OBS and GLDAS.

The overestimations in reanalyses occur in the monsoon season and the underestimations in DDM and CPM occur in the non-monsoon season. Large evapotranspiration biases exist over the vegetated ground which exert large impacts on the TP-average biases for growing season.
Numerical simulation of fluid injection in faulted and fractured rocks based on a fully-coupled hydro-mechanical model
Authors: Qinghua Lei , Tsang Chin-Fu
Published: March 2021

We present a fully-coupled hydro-mechanical simulation of fluid injection-induced activation of pre-existing discontinuities, propagation of new damages, development of seismic activities, and alteration of network connectivity in naturally faulted and fractured rocks, which are represented using the discrete fracture network approach. We use the finite element method to compute the multiphysical fields including stress, strain, damage, displacement, and pressure by solving governing and constitutive equations of coupled solid and fluid domains. Essential hydro-mechanical coupling mechanisms are honoured such as pore pressure-induced shear slip of natural discontinuities, poro-elastic response of rock matrix, and stress-dependent permeability/storativity of both fractures and rocks. We use the numerical model developed to investigate the hydro-mechanical behaviour of deeply buried fractured rocks and fault zones in response to high-pressure fluid injection, with a specific focus on the system either below or above the percolation threshold. We observe a strong control of fracture network connectivity on the damage emergence, seismicity occurrence and connectivity change in the rock mass subject to hydraulic stimulation. We highlight the strong poro-elastic effect that tends to drive heterogeneous connectivity evolution of fracture systems during fluid injection. The results of our research and insights obtained have important implications for injection-related geoengineering activities such as the development of enhanced geothermal systems and extraction of hydrocarbon resources.
How detailed do cloud microphysics need to be in climate models?
Authors: Proske Ulrike , Ferrachat Sylvaine , Neubauer David , Lohmann Ulrike
Published: March 2021

Clouds are of major importance for the climate system, but the radiative forcing resulting from their interaction with aerosols remains uncertain. To improve the representation of clouds in climate models, the parameterisations of cloud microphysical processes (CMPs) have become increasingly detailed. However, more detailed climate models do not necessarily result in improved accuracy for estimates of radiative forcing (Knutti and Sedláček, 2013; Carslaw et al., 2018). On the contrary, simpler formulations are cheaper, sufficient for some applications, and allow for an easier understanding of the respective process' effect in the model.

This study aims to gain an understanding which CMP parameterisation complexity is sufficient through simplification. We gradually phase out processes such as riming or aggregation from the global climate model ECHAM-HAM, meaning that the processes are only allowed to exhibit a fraction of their effect on the model state. The shape of the model response as a function of the artificially scaled effect of a given process helps to understand the importance of this process for the model response and its potential for simplification. For example, if partially removing a process induces only minor alterations in the present day climate, this process presents as a good candidate for simplification. This may be then further investigated, for example in terms of computing time.
The resulting sensitivities to CMP complexity are envisioned to guide CMP model simplifications as well as steer research towards those processes where a more accurate representation proves to be necessary.

 

Carslaw, Kenneth, Lindsay Lee, Leighton Regayre, and Jill Johnson (Feb. 2018). “Climate Models Are Uncertain, but We Can Do Something About It”. In: Eos 99. doi: 10.1029/2018EO093757

Knutti, Reto and Jan Sedláček (Apr. 2013). “Robustness and Uncertainties in the New CMIP5 Climate Model Projections”. In: Nature Climate Change 3.4, pp. 369–373. doi: 10.1038/nclimate1716
Recent progress in the study of fine-scale physical-biological coupling in the Mediterranean Sea.
Authors: Tzortzis Roxane , Doglioli Andrea M. , Barrillon Stéphanie , Petrenko Anne A. , d'Ovidio Francesco , Izard Llyod , Thyssen Melilotus , Bhairy Nagib , Pascual Ananda , Barceló-Llull Bàrbara , Cyr Frédéric , Tedetti Marc , Garreau Pierre , Dumas Franck , Bordois Lucie , Comby Caroline , Rousselet Louise , Gregori Gérald
Published: March 2021

The fine scales are defined here as oceanic dynamical features (eddies, fronts and filaments) generally induced by mesoscale interactions and frontogenesis, and often associated with intense vertical exchanges. These processes are characterized by horizontal scales of 1–10 km with a relatively short lifetime of days/weeks to months. This temporal scale is similar to that of many biological processes, such as, phytoplankton growth, suggesting a physical and biological coupling. Numerical simulations and satellite observations have allowed the characterization of this regime highlighting the role played by these fine scales on structuring the phytoplankton community. To better understand this coupling mechanism, physical and biological in situ measurements are necessary. However, the observations of fine scales remains challenging due to the difficulties of sampling at high spatio-temporal frequency (~km ~daily).

Over the past few years, the Mediterranean Sea has become a lab for developing fine scale in situ strategies. Indeed, a series of campaigns using a satellite based adaptative and Lagrangian strategy coupled with a high-resolution physical-biological sampling, have been performed in order to follow and describe fine scale structures. Following this strategy, the PROTEVSMED-SWOT 2018 cruise has been leaded in the South of the Balearic Islands, with a particular attention to correlate the Lagrangian sampling with the temporal phytoplankton growth, in order to reconstruct the phytoplankton diurnal cycle. Multidisciplinary in situ sensors have allowed to identify a frontal area with a dynamic vertical circulation. Furthermore, the presence of two Atlantic waters, at different stages of mixing associated with various abundances of several phytoplankton groups, corroborated that fine scales must be dynamical barriers to transport, as previous modeling studies have proposed. In order to better understand fine scale mechanisms, the Protevs Gibraltar cruise was performed in the Strait of Gibraltar in October 2020. This region of study is characterized by an important exchange of Mediterranean and Atlantic waters, and also by an intense circulation that generates energetic processes, which make it a favorable place for the formation of fine scale structures.

The new knowledge acquired with these studies paves the way to the future BIOSWOT-Med campaign planned for 2022 in the western Mediterranean Sea under the future SWOT satellite crossover tracks.