bluuebunny/crossref_metadata_2025 huggingface dataset:
Unusual old water ages of an Alpine karst spring (Central Eastern Alps): Hydrogeology, isotopes (18O/2H, 3H, 3He, 14C) and tracer gas analyses (CFC-11,-12,-113, SF6)
Authors: Kralik Martin , Zwack Thomas , Stumpp Christine
Published: March 2021

Aim of the study was to delineate an appropriate wide-ranging drinking water protection zone for the tapped main Walchhof spring, which is part of the public water supply of the small city of Radstadt in the region of Salzburg, Austria. The immediate hydrographic catchment area of the spring was geological mapped, various electric conductivity measurements at the river Taurach and its tributaries were carried out to detect potential high mineralised (SO4) karst water influx and fluorescence tracer tests were performed on the adjacent hydrographic catchment area above the tapped main spring. The Walchhof springs discharge approximate 500 L/s in a complex central-alpine setting within a tectonic window structure built of the Radstadt nappe with permeable carbonate rocks overthrusted by the Schladming-Seckau nappe with mostly non-permeable phyllite rocks. To identify the mean altitude of the catchment area and the Mean Residence Time (MRT) of the spring waters a combination of isotopes 2H/18O, 3H/3He, 13C/14C and tracer gases (CFC, SF6) was analysed. The 2H/18O-isotopes were analysed on weekly samples during 2019. 3H/3He, 13C/14C and (CFC, SF6) were sampled twice in April and October 2019.  The results indicate a wide-ranging hydrogeological catchment area (max. 90km2) at a mean altitude of 2000 ± 200 m and a mixture of old (10-20 yrs) and very old (several thousand years) waters. However, heavy rainfall and snow melt events can add (< 10%) very young water (MRT: days-weeks) to the tapped main Walchhof spring. The combination of these methods allows to reduce the wide-ranging drinking water protection zone mainly to the immediate hydrographic catchment area.
Atmospheric Gravity Waves in ADM-Aeolus Wind Lidar Observations
Authors: Banyard Timothy , Wright Corwin , Hindley Neil , Halloran Gemma , Krisch Isabell , Kaifler Bernd , Hoffmann Lars
Published: March 2021

As the first Doppler wind lidar in space, ADM-Aeolus provides us with a unique opportunity to study the propagation of gravity waves (GWs) from the surface to the tropopause and UTLS. Existing space-based measurements of GWs in this altitude range are spatially limited and, where available, use temperature as a proxy for wind perturbations. Thus, space-borne wind lidars such as Aeolus have the potential to transform our understanding of these critically-important dynamical processes. Here, we present the first observations of GWs in Aeolus data. We analyse a case study of a large orographic GW over the Southern Andes in July 2019 which is clearly visible in the horizontal wind. This example demonstrates the capability of Aeolus to measure the phase structure of GWs from near the surface up into the stratosphere. We validate these results against temperature-based observations from the AIRS nadir sounder and CORAL lidar, and also against ERA5 wind and temperature. There is close agreement in phase structure between Aeolus and the validation datasets, and with a near-identical observed vertical wavelength and spatial location. This case study suggests that data from Aeolus, and similar next-generation space-borne wind lidars, could play a critical role in constraining future model GW parameterisations, with the potential to significantly broaden our understanding of atmospheric dynamics.
Exploring de formation of the Arsia Mons Elongated Cloud on Mars
Authors: Hernandez-Bernal Jorge , Sánchez-Lavega Agustín , Del Río-Gaztelurrutia Teresa
Published: March 2021

In a recent work (Hernández-Bernal et al. 2020) we reported the existence and properties of the AMEC (Arsia Mons Elongated Cloud). This cloud appears every martian year around the southern solstice following a quick daily cycle, it expands up to 1800 km after sunrise and disappears before noon. While in the previous work we made an extensive observational study, a number of questions remain unsolved, including the specific specific set of atmospheric conditions that originates this particular cloud at this moment of the year, and why other near volcanoes do not exhibit analogous clouds. In this work we explore, based on models, the physical conditions of the atmosphere around Arsia Mons, such as temperature gradients, winds, and water vapor distribution, as a first step to try to understand this particular cloud.

References:

Hernández-Bernal, J., Sánchez-Lavega, A., Río-Gaztelurrutia, T. D., Ravanis, E., Cardesín-Moinelo, A., Connour, K., ... & Hauber, E. An Extremely Elongated Cloud over Arsia Mons Volcano on Mars: I. Life Cycle. Journal of Geophysical Research: Planets, DOI: 10.1029/2020JE006517
Nondestructive data analysis for pavement profile evaluation
Authors: Plati Christina , Gkyrtis Konstantinos , Loizos Andreas
Published: March 2021

Highway pavements serve the need for safe transportation of human being and freights, so their condition deserves continuous monitoring and assessment. However, pavements are most often monitored in terms of their surface performance evaluation. Either with or without surface distresses, excessive pavement unevenness and/or texture loss may lead to a reduced road users’ satisfaction. Most often, the pavement surface condition is sensed through laser profilers that operate at traffic speeds. Once detected through the stand-alone use of laser profilers, pavement roughness along a pavement surface may be of major concern for the related agencies, since the root causes of roughness issues are in most cases unknown.

Excessive unevenness might sometimes be interrelated with structural issues within one or more pavement layers or even issues within the pavement foundation support. Traditionally, coring and boreholes are considered suitable to detect the condition of pavement surface layers and pavement substructure respectively. However, these processes are destructive and time-consuming. On the contrary, Non-Destructive Testing

(NDT) can be alternatively used to rapidly evaluate potential structural problems at areas with roughness issues and identify areas for further investigation. A popular method to assess the pavement structural integrity is the use of nondestructive deflectometric tests, including the Falling Weight Deflectometer (FWD). This kind of testing outperforms the traditional approach; thus it is both desirable and practical.

On these grounds, related research is pursued towards integrating pavement profile and deflectometric data in order to further evaluate indications of increased pavement roughness. In particular, Long Term Pavement Performance (LTPP) data including deflectometric and pavement profile data is used. Additional sensing data through geophysical inspections with the Ground Penetrating Radar (GRP) is used to assist the overall pavement assessment. The study demonstrates the power of pavement sensing data in order to provide the related agencies with cost-effective and reliable evaluation methods and approaches.
Optimal choice of the number and configuration of VLBI Global Observing System in India
Authors: Singh Shivangi , Goyal Ropesh , Balasubramanian Nagarajan , Devaraju Balaji , Dikshit Onkar
Published: March 2021

The need of the geodetic VLBI stations in South Asia region has been discussed and suggested for decades to have a uniform global VLBI network and relatively more accurate realisation of ITRF. With the recent initiative of National Centre for Geodesy, India, setting up of a few VLBI stations in the country is being proposed. India spans from latitude 8.4º N to 37.6º N and longitude 68.7º E to 97.25º E and encompasses a diversified topography with a plethora of geodynamical activities. Along with contributions to the international geodetic campaigns, we would like to choose the locations of these VGOS stations so that these can be an aid to the Indian geodetic infrastructure along with several other studies of national importance. For multitude of reasons, the prospective sites for establishing VGOS stations in India are: 1) IIST Ponmudi campus, 2) Mt. Abu Observatory, PRL, 3) IIT Kanpur and 4) NE-SAC, Shillong. The approximate longitudinal extent of 20º and latitudinal extent of 18º between these prospective sites are worth exploiting for determining the angle of the Earth rotation (dUT1) and polar motion, respectively. In this study, we present the comparison results of the solutions with and without additional VGOS station in India. For this, we first generated an optimised schedule for a classical VGOS/R1 session, using VieVS, with existing stations using the comparatively more important optimisation criteria (duration, sky-coverage, number of observations and idle time) and corresponding weight factors. The simulation result of the best schedule is kept as our reference solution. With respect to this reference network, we further generated optimised schedules by including the prospective stations from India (different combinations of the four proposed stations). We present our analysis due to change in network geometry, and therefore, we compare the variations in the repeatability values of the estimated EOPs with the addition of VGOS station(s) in India.
Combining Distributed Acoustic Sensing and Beamforming in a Volcanic Environment on Mount Meager, British Columbia.
Authors: Klaasen Sara , Paitz Patrick , Dettmer Jan , Fichtner Andreas
Published: March 2021

We present one of the first applications of Distributed Acoustic Sensing (DAS) in a volcanic environment. The goals are twofold: First, we want to examine the feasibility of DAS in such a remote and extreme environment, and second, we search for active volcanic signals of Mount Meager in British Columbia (Canada). 

The Mount Meager massif is an active volcanic complex that is estimated to have the largest geothermal potential in Canada and caused its largest recorded landslide in 2010. We installed a 3-km long fibre-optic cable at 2000 m elevation that crosses the ridge of Mount Meager and traverses the uppermost part of a glacier, yielding continuous measurements from 19 September to 17 October 2019.

We identify ~30 low-frequency (0.01-1 Hz) and 3000 high-frequency (5-45 Hz) events. The low-frequency events are not correlated with microseismic ocean or atmospheric noise sources and volcanic tremor remains a plausible origin. The frequency-power distribution of the high-frequency events indicates a natural origin, and beamforming on these events reveals distinct event clusters, predominantly in the direction of the main peaks of the volcanic complex. Numerical examples show that we can apply conventional beamforming to the data, and that the results are improved by taking the signal-to-noise ratio of individual channels into account.

The increased data quantity of DAS can outweigh the limitations due to the lower quality of individual channels in these hazardous and remote environments. We conclude that DAS is a promising tool in this setting that warrants further development.
Modelling multi-fissure zones above buried rock ridges in subsiding basins
Authors: yueting Li , Teatini Pietro , Ye Shujun , Franceschini Andrea , Frigo Matteo , Zoccarato Claudia
Published: March 2021

Aseismic earth fissures due to the excessive groundwater exploitation have caused seriously damage in many subsiding sedimentary basins worldwide. Generally, multiple fissures almost parallel to each other with equal distances are prone to develop where a compacting aquifer system overlies impermeable and/or incompressible ridges. Here, an advanced finite-element interface-elements modelling approach is employed to understand this process within unfaulted sedimentary sequences. A simplified geological setting is initially used to investigate the effect of the ridge slope on ruptures behaviors. Then, we reproduce the case of Guangming village, China. In both the proposed scenarios, the model simulates the occurrence of multi-fissures that initiate at land surface and propagate downward, as observed in the sites. The earth fissures are formed as a result of the combination of tensile stress (bending condition) and shear stress (shearing conditions) accumulation around and above the tip and the slopes of the ridge, respectively. The numerical outcomes indicate that the steeper ridge results in higher magnitude stress accumulation above the ridge tip which favors the formation of fissures with significant opening and small or null offset, but at expense of the reduction in stress accumulation area and fissure distribution. In Guangming case, the outcomes show that two ruptures started sliding and only one year later a central fissure opened and propagated down to 15-30 m depth. The simulated maximum opening and sliding of the central and side fissures, respectively, approximate 30 cm, which are almost in agreement with the observations. The numerical results prove that the proposed modeling approach is an effective way to predict and analyze multi-fissure onset and development in subsiding basins.
Deployment, calibration, and efficiency of SHUD model in cold and arid watersheds
Authors: Shu Lele , Chen Hao , Meng Xianhong
Published: March 2021

The hydrologic model is ideal for experimenting and understanding the water movement and storage in a watershed from the upper mountain to the river outlet. Nevertheless, the model's performance, suitability, and data availability are the primary challenge for a modeler. This study introduces the Simulator for Hydrologic Unstructured Domains (SHUD), a surface-subsurface integrated hydrological model using the semi-discrete Finite Volume Method. Though the SHUD applies a fine time-step (in minutes) and flexible spatial domain decomposition (m to km) to simulate the fully coupled surface-subsurface hydrology, the model can solve the watershed-scale problem efficiently and dependably. Plenty of applications in the USA proved the SHUD model's performance and suitability in the humid and data-rich watersheds.  

In this research, we demonstrate the SHUD model deployment in two data-scarce watersheds in the northwest of China with global datasets, validate the simulations against local observational data, and assess the SHUD model's efficiency and suitability.  The one is the Upstream Heihe River (UHR), which is a typical semi-arid mountainous watershed.  The other is Yellow River Source (YRS), the upstream of Yellow River, contributing more than 50% of total discharge. The results, figures, and analysis based on SHUD simulations under global datasets highlight the model's suitability and efficiency in data-limited watersheds, even ungaged ones. The SHUD model is a useful modeling platform for hydrology and water-related coupling studies.
Identifying multi-day to sub-daily supraglacial lake change in Greenland from Sentinel 2 and Landsat 8 imagery using Google Earth Engine
Authors: Li Qiao , Lea James , Brough Stephen
Published: March 2021

Supraglacial lakes (SGLs) are a major component of Greenland’s surface hydrology and mass balance. Monitoring their evolution at multi-day to sub-daily timescales has traditionally been performed by relatively low-resolution sensors such as MODIS Terra, though opportunities exist for using higher spatial resolution sensors at high latitudes.

In this study, we take advantage of frequent orbital crossovers of Sentinel 2 and Landsat 8 imagery at high latitudes to monitor lakes at multi-day to sub-day temporal resolution, and spatial resolutions up to/over an order of magnitude higher than MODIS Terra (10 m to 30 m, compared to ~250 m for MODIS Terra). Through leveraging the cloud computing resources of Google Earth Engine (GEE), we have developed a workflow to track the evolution of lakes for all available Sentinel 2 and Landsat 8 images over a melt season.

Our workflow builds on the approach of Moussavi et al. (2020) that was developed for Antarctica, implementing it within GEE to explore its sensitivity and suitability for application to the catchment of the North East Greenland Ice Stream (NEGIS) for the 2019 melt season. To improve the efficiency of analysis, we analyse 282 large lakes (>0.125 km^2) that were previously identified through analysis of MODIS Terra imagery. All lake outlines are appended with image ID and lake area metadata to facilitate subsequent analysis, and allow each lake outline to be traced back to the original image that it was derived from. Our approach is able to monitor lake growth and drainage at unprecedented spatial and temporal resolutions over a large area, allowing the widespread characterization of seasonal lake evolution.
Innovative software solutions for subsea positionings
Authors: Morvan Pierre-Yves , Bagot Gary
Published: March 2021

Improving operational efficiency is a recurring challenge for subsea operations. Throughout the life of a field, from construction up to decommissioning, several subsea vehicles will be deployed to cover various tasks to perform underwater observations. An ROV or AUV assigned to a specific task will require multiple positioning sensors (LBL, USBL, INS…) to complete its mission. Defining the “good enough” subsea positioning strategy, i.e. to ensure a minimum accuracy without compromise on safety, can be a complex exercise. For instance, an overestimation of the LBL transponders required will directly induce vessel time and finally costly operations. On the other hand, a certain level of positioning redundancy may be requested for a vehicle operating close to a subsea asset in production.

To ease the design and monitoring of a subsea vehicle navigation, iXblue has developed an integrated solution. Not only has the company broadened its product range with the new intelligent Canopus LBL Transponder and the new generation Ramses transceiver, but with Delph Subsea Positioning Software, iXblue now provides a complete integrated solution for subsea positioning that goes a step further by bringing significant efficiency. Divided in 4 modules (LBL Array Planning, Navigation Simulation, Operations, DelphINS) with an intuitive user interface, Delph Subsea Positioning (DSP) is an integrated software suite for the preparation, the operation and the post-processing of iXblue positioning devices (USBL, LBL and INS).
Multi-temporal analysis of optical remote sensing for time-series displacement of gravitational mass movements, Sattelkar, Obersulzbach Valley, Austria
Authors: Hermle Doris , Gaeta Michele , Keuschnig Markus , Mazzanti Paolo , Krautblatter Michael
Published: March 2021

Remote sensing for natural hazard assessment and applications offers data on even vast areas, often difficult and dangerous to access. Today, satellite data providers such as PlanetLabs Inc. and the European Copernicus program provide a sub-weekly acquisition frequency of high resolution multispectral imagery. The availability of this high temporal data density suggests that the detection of short-term changes is possible; however, limitations of this data regarding qualitative, spatiotemporal reliability for the early warning of gravitational mass movements have not been analysed and extensively tested.

This study analyses the effective detection and monitoring potential of PlanetScope Ortho Tiles (3.125 m, daily revisit rate) and Sentinel-2 (10 m, 5-day revisit) satellite imagery between 2018 and 2020. These results are compared to high accuracy UAS orthoimages (0.16 m, 5 acquisitions from 2018-2020). The analysis is conducted based on digital image correlation (DIC) using COSI-Corr (Caltech), a well-established software and the newly developed IRIS (NHAZCA). The mass wasting processes in a steep, glacially-eroded, high alpine cirque, Sattelkar (2’130-2’730 m asl), Austria, are investigated. It is surrounded by a headwall of granitic gneiss with a cirque infill characterised by massive volumes of glacial and periglacial debris including rockfall deposits. Since 2003 the dynamics of these processes have been increased, and between 2012-2015 rates up to 30 m/a were observed.

Similar results are returned by the two software tools regarding hot-spot detection and signal-to-noise ratio; nonetheless IRIS results in an overall better detection, including a more delimitable ground motion area, with its iterative reference and secondary image combination. This analysis is supported by field investigations as well as clearly demarcated DIC-results from UAS imagery. Here, COSI-Corr shows limitations in the form of decorrelation and ambiguous velocity vectors due to high ground motion and surface changes for very high resolution of this input data. In contrast, IRIS performs better returning more coherent displacement rates. The results of both DIC tools for satellite images are affected by spatial resolution, data quality and imprecise image co-registration.

Knowledge of data potential and applicability is of high importance for a reliable and precise detection of gravitational mass movements. UAS data provides trustworthy, relative ground motion rates for moderate velocities and thus the possibility to draw conclusions regarding landslide processes. In contrast satellite data returns results which cannot always be clearly delimited due to spatial resolution, precision, and accuracy. Nevertheless, iterative calculations by IRIS improve the validity of the results.
Benefits of ice-ocean coupling for medium-range forecasts in polar and sub-polar regions
Authors: Day Jonathan , Keeley Sarah , Mogensen Kristian , Tietsche Steffen , Magnusson Linus
Published: March 2021

Dynamic sea ice and ocean have long been recognised as an important components in the Earth System Models used to generate climate change projections and more recently seasonal forecasts. However, the benefit of forecasts on the timescales of days to weeks has received less attention. Until recently it was assumed that sea-ice-ocean fields change so slowly that it is acceptable to keep them fixed in short and medium-range forecasts. However, at the ice edge the presence of sea ice dramatically influences surface fluxes, particularly when the overlying atmosphere is much colder than the open ocean so errors in the position of the sea ice, caused by simply persisting this field, have the potential to degrade atmospheric skill. To address this and similar issues, the European Centre for Medium-range Weather Forecasts (ECMWF) recently took the pioneering step of coupling a dynamic–thermodynamic sea ice-ocean model to the Integrated Forecast System, developing the first coupled medium-range forecasting system. This was a major step towards making ECMWF’s forecasts seamless across all timescales.

In this study we assess the benefits of including coupled sea-ice ocean processes in the medium-range by comparing set of ten-day forecasts with and without dynamic ice-ocean coupling, focussing on forecast performance at the edge of the sea ice and in the surrounding region. We demonstrate that dynamic coupling improves forecasts of the sea ice edge at all leadtimes. Further, the skill gained is larger during periods when the ice edge is advancing or retreating rapidly. We will also explore whether dynamic coupling has an impact on forecast skill in atmospheric parameters downstream of the ice edge.  
A dynamic rhizosphere interplay between tree roots and soil bacteria under drought stress
Authors: Oppenheimer-Shaanan Yaarao , Jakoby Gilad , Starr Maya Laurenci , Karliner Romiel , Eilon Gal , Itkin Maxim , Malitsky Sergey , Klein Tamir
Published: March 2021

Root exudates are thought to play an important role in plant-microbial interactions. In return, soil bacteria can increase the bioavailability of soil minerals, which is typically decreasing in situations such as drought. Here we describe an exudate-driven microbial priming on Cupressus saplings grown outside in forest soil in custom-made rhizotron boxes. A 1-month imposed drought and inoculations with Bacillus subtilis and Pseudomonas stutzeri, bacteria species forest soil isolation, were applied in a factorial design. We revealed that both bacteria associated with Cupressus roots and were more abundant in rhizosphere than in bulk soil. Moreover, root exudation rate increased in inoculated trees under drought with >100 first identified metabolites from Cupressus roots. Among these metabolites, phenolic acid compounds, quinate, and others, were used as carbon and nitrogen sources by both bacterial species. Furthermore, soil phosphorous bioavailability was maintained only in inoculated trees, where a drought-induced decrease in leaf phosphorus and iron was prevented. We provide evidence that changes in exudation rate and composition under drought and bacteria inoculation, support the idea of root recruitment of beneficial bacteria. In turn, trees secreted further carbon source to the rhizosphere and hosted more bacteria, benefited from improved nutrition.
A Bayesian Framework for Aftershock Forecasting and Testing
Authors: Shcherbakov Robert
Published: March 2021

Earthquakes trigger subsequent earthquakes. They form clusters and swarms in space and in time. This is a direct manifestation of the non-Poisson behavior in the occurrence of earthquakes, where earthquake magnitudes and time intervals between successive events are not independent and are influenced by past seismicity. As a result, the distribution of the number of earthquakes is no longer strictly Poisson and the statistics of the largest events deviate from the GEV distribution. In statistical seismology, the occurrence of earthquakes is typically approximated by a stochastic marked point process. Among different models, the ETAS model is the most successful in reproducing several key aspects of seismicity. Recent analysis suggests that the ETAS model generates sequences of events which are not Poisson. This becomes important when the ETAS based models are used for earthquake forecasting (Shcherbakov et al., Nature Comms., 2019). In this work, I consider the Bayesian framework combined with the ETAS model to constrain the magnitudes of the largest expected aftershocks during a future forecasting time interval. This includes the MCMC sampling of the posterior distribution of the ETAS parameters and computation of the Bayesian predictive distribution for the magnitudes of the largest expected events. To validate the forecasts, the statistical tests developed by the CSEP are reformulated for the Bayesian framework. In addition, I define and compute the Bayesian p-value to evaluate the consistency of the forecasted extreme earthquakes during each forecasting time interval. The Bayesian p-value gives the probability that the largest forecasted earthquake can be more extreme than the observed one. The suggested approach is applied to the recent 2019 Ridgecrest earthquake sequence to forecast retrospectively the occurrence of the largest aftershocks (Shcherbakov, JGR, 2021). The results indicate that the Bayesian approach combined with the ETAS model outperformed the approach based on the Poisson assumption, which uses the extreme value distribution and the Omori law.
Statistical analysis of mesoscale eddies and their effects on chlorophyll-a concentration in the Indo Pacific warm pool
Authors: Long Shuang , Dong Qing , Song Wanjiao
Published: March 2021

As one of the most significant physical processes in the ocean, mesoscale eddies play an import role in the local distributions of temperature, salinity, ocean current field and ecosystem through vertical mixing and horizontal advection. In addition, mass transport is importantly affected by the propagation of mesoscale eddies. Researches on the characteristics of mesoscale eddies and their effects on chlorophyll-a concentration in the Indo Pacific Warm Pool (20°S~20°N，60°E~170°W), the key area influencing the global climate change, help to further understand the bio-physical coupling processes in this domain. Using the remote sensing data from 1998 to 2018, combined with singular value decomposition, correlation analysis and other statistical methods, we have studied the distribution characteristics of mesoscale eddies with lifetime exceeding 4 weeks and the correlation with chlorophyll-a concentration in the Indo Pacific Warm Pool. The short-lived mesoscale eddies account for more than 70.0% and most of mesoscale eddies are nonlinear and propagate west. The seasonal numbers of mesoscale eddies vary insignificantly in the whole domain and plenty of the eddies generate in sea domains of 5°S~20°S and 5°N~20°N. The number of mesoscale eddies has little effect on chlorophyll-a concentration and the correlation between the kinetic energy of mesoscale eddies and chlorophyll-a concentration show both positive and negative.
Interspecific soil water partitioning as a driver of increased productivity in a diverse mixed Mediterranean forest
Authors: Rog Ido , Tague Christina , Jakoby Gilad , Megidish Shacham , Yaakobi Assaf , Wagner Yael , Klein Tamir
Published: March 2021

It has been assumed that mixing of species with high physiological diversity reduces competition over water and light resources, compared to single-species forests. Although several mechanisms to explain this observation have been proposed, empiric evidence is lacking. Here we studied water-use dynamics at a monthly resolution for two years in five key tree species in a mature, mixed, evergreen, Mediterranean forest. Root distribution was measured with DNA barcoding and soil cores. Measurements at the tree-scale were up-scaled using an ecosystem model of coupled water, carbon and energy fluxes (Regional Hydro Ecologic Simulation System, RHESSys). Tree species showed contrasting water-use patterns, with year-round activity in angiosperms, and mostly wet season-activity in gymnosperms. Water-use patterns matched the rooting patterns, with the deep- and shallow-rooted Ceratonia and Cupressus, showing year-round and seasonal behaviors, respectively. RHESSys simulations captured well the species-specific behaviors in the mixed forest, and were further applied to simulate monocultures of each of the species, which proved less productive than the mixed forest. Our results provide evidence for niche partitioning of the soil water resource among co-habiting tree species. This partitioning is driven by spatiotemporal species differences in rooting depth and eco-physiology, and facilitates the higher productivity of the mixed forest.
MOPGA/Improving Air Quality in West Africa: Low-cost sensors as a solution to improve the understanding of spatial and temporal variability in urban air pollution
Authors: Bahino Julien , Giordano Michael , Yoboué Véronique , Ochou Arsène , Galy-Lacaux Corinne , Liousse Cathy , Amegah Kofi , Hugues Allison , Nimo James , Beekmann Matthias , Subramanian Ramachandran
Published: March 2021

This study was carried out within the framework of the Improving Air Quality in West Africa (IAQWA) project funded by the Make Our Planet Great Again (MOPGA) program. In recent years, West African countries have experienced an economic upturn driven by GDP growth of nearly 3.7% in 2019 (AfDB, 2020). This economic boom is mainly felt in the cities where it promotes the construction of highway infrastructure, real estate development, and industry. All these activities are sources of air pollution. Unfortunately, there is almost no air quality monitoring in these cities partly due to the high cost of monitoring instruments. Low-cost air quality monitoring instruments can help improve the spatial and temporal resolution of measurements at relatively lower cost. However, the installation of these instruments in West African environments characterized by high relative humidity requires their calibration through collocation with reference instruments. The IAQWA project aims to improve our understanding of air pollutants such as fine particulate matter mass (PM2.5), ozone (O3), nitrogen oxides (NOx), sulfur dioxide (SO2), and carbon monoxide (CO) in Abidjan and Accra, two major West African capitals, through the deployment of Real-time Affordable Multi-Pollutant (RAMP) monitors.

Since February 2020, five RAMPs have been installed and are operating continuously at various sites in Abidjan and Lamto in Cote d'Ivoire, and four RAMPs have been operating in Accra, Ghana. Some of the RAMPs have been collocated with PM and/or NOx reference instruments. At other sites the RAMPs have been collocated with INDAAF passive samplers and passive aerosol collectors. These collocations have allowed for the development of calibration models for these low-cost sensors. The performance of these calibration models is presented here along with the diurnal and seasonal variations of air pollution at the different sites in Abidjan and Accra. These results will eventually be used to improve our understanding of the drivers of air pollution in these major West African cities, which is essential to choosing sustainable development pathways in the future.
Upscaled shallow water modeling with SW2D-Lemon for urban flood simulation
Authors: Caldas Steinstraesser Joao Guilherme , Delenne Carole , Finaud-Guyot Pascal , Guinot Vincent , Kahn Casapia Joseph Luis , Rousseau Antoine
Published: March 2021

We present a new multi-OS platform named SW2D-LEMON (SW2D for Shallow Water 2D) developed by the LEMON research team in Montpellier.

SW2D-LEMON is a multi-model software focusing on shallow water-based models. It includes an unprecedented collection of upscaled (porosity) models used for shallow water equations and transport-reaction processes. Porosity models are obtained by averaging the two-dimensional shallow water equations over large areas containing both a water and a solid phase. The size of a computational cell can be increased by a factor 10 to 50 compared to a 2D shallow water model, with CPU times reduced by 2 to 3 orders of magnitude. Applications include urban flood simulations as well as flows over complex topography. Besides the standard shallow water equations (the default model), several porosity models are included in the platform: (i) Single Porosity, (ii) Dual Integral Porosity, (iii) Depth-dependent Porosity. Various flow processes (friction, head losses, wind, momentum diffusion, precipitation/infiltration) can be included in a modular way by activating specific execution flags.

Classical input data are required by SW2D-Lemon software: mesh file (several formats available) with elements having an arbitrary number of edges; geometric and hydraulic parameter fields: bathymetry, porosity, Boussinesq/Coriolis momentum distribution coefficient, friction coefficient fields, etc.; initial and boundary conditions (several types available) and forcings (wind, rainfall).

SW2D can be used in two ways: in command-line mode or via a dedicated graphic user interface (GUI). Both features are available on all Windows, MacOS and Linux operating systems. SW2D is available under three license modes: Academic Research (source code, developer manual and basic configurations are freely available in the framework of a scientific partnership with the LEMON team), Industry and education.

Various real-world test cases will be presented to illustrate the potential of SW2D and the contribution of porosity based models to urban flood modelling:
- Flood simulation on Sacramento city induced by the breach of a dike;- Marine submersion on Valras Plage;- Fast rain flood on the Abidjan Riviera district.
 
Forecasts of tropical cyclones in the Bay of Bengal in a regional convection-permitting atmosphere-ocean coupled model
Authors: Saxby Jennifer , Crook Julia , Birch Cathryn , Holloway Chris , Lewis Huw , Peatman Simon , Schwendike Juliane
Published: March 2021

Tropical cyclones (TCs) forming over the Bay of Bengal can cause devastation when they make landfall in India and Bangladesh; accurate prediction of their track and intensity is essential for disaster management. TC intensity is moderated by heat, momentum and moisture exchanges between the atmosphere and ocean. In recent years there have been significant improvements in the skill of TC forecasts due to the implementation of coupled atmosphere-ocean models and high-resolution models capable of explicitly resolving small-scale physical processes influencing storm development.

 

This study evaluates the representation of six TCs in the Bay of Bengal from 2016 to 2019, using both a Met Office Unified Model atmosphere-only configuration (ATM) with 4.4 km grid spacing, and coupled to a 2.2 km resolution NEMO (Nucleus for European Models of the Ocean) ocean model (CPL). To determine the impact of coupling on wind-driven mixing and ocean-atmosphere heat exchange, forecast sea surface temperature (SST) is compared to observations. The impact of coupling on track position and storm intensity is evaluated using predictions of minimum sea level pressure (MSLP) and 10 m maximum sustained winds (MSW). Representation of TC dynamics is assessed by analysing storm structure, using radius of maximum winds and rain rate asymmetry.

 

Results from the three most intense TC case studies (Fani, Titli, and Vardah) show that SSTs in ATM are too high, while SSTs in CPL are slightly too low, with an overestimation of the cooling response in TC wakes. TC track position errors are small, but intensity error metrics for MSLP and MSW show biases relative to observations. Peak intensity is overestimated for Titli and Vardah in the ATM model configuration; the CPL model configuration generally produces weaker storms than the ATM model configuration. Wind speeds outside the storm centre are high compared to observations, with a greater bias in the ATM model configuration.  Both model configurations produce accurate predictions of radius of maximum winds and rain rate asymmetry, suggesting a good representation of TC dynamics. Much of the variation in rain rate asymmetry in the forecasts can be explained by variations in wind shear.
Impact of surface roughness on dust occurrence frequency over arid regions
Authors: Klose Martina , Pérez García-Pando Carlos , Ginoux Paul , Miller Ron L.
Published: March 2021

Soil dust aerosol created by wind erosion of arid and semi-arid surfaces dominates climate effects over large areas of the Earth. To represent the dust cycle, Global Earth System Models (ESMs) typically prescribe preferential dust sources phenomenologically using empirical source scaling functions. While this approach has helped to compensate for a lack or inaccuracy of soil and surface input data to models, it potentially limits progress in the representation of the global dust cycle, because such strong empirical constraints make models less sensitive to parameters known to affect dust emission, and thus potentially insensitive to changes in climate. Here we investigate the link between surface roughness due to non-erodible elements such as vegetation, pebbles and rocks, and the spatial patterns of dust activity. Using two different satellite-based methods to represent roughness within an atmospheric dust transport model, we evaluate the impact of surface roughness on the spatial distribution of dust optical depth occurrence frequency observed from satellite by both reducing the atmospheric momentum available for particle entrainment and protecting the surface from dust emission. We test the variability of our results across conceptually different parameterizations of dust emission and drag partition. Our results suggest that the spatial patterns of dust activity are largely determined by surface roughness, not only in semi-arid, but also in arid regions, where green vegetation is sparse or absent. 
Potential soil organic carbon sequestration with cover crops in German croplands
Authors: Seitz Daria , Fischer Lisa Mareen , Dechow Rene , Don Axel
Published: March 2021

Cover crops have been suggested to preserve or even increase the soil organic carbon (SOC) stocks in croplands which can contribute to soil fertility and climate change mitigation. Cover crop cultivation increased in most European countries during the last years. However, it remains unquantified how many additional cover crops can be integrated into existing crop rotations. Moreover, there are no realistic quantitative estimates of the SOC sequestration potential of implementing additional cover crops in Germany.

We analyzed recent German crop rotations obtained from the first German Agricultural Soil Inventory for available cultivation windows (winter fallows) for cover crops, and we simulated the SOC sequestration potential of additional cover crops in the topsoil using a SOC model ensemble consisting of RothC and C-TOOL. In order to estimate a reasonable carbon input via the cover crops’ biomass, we developed a new allometric function which takes the effect of the weather and the seeding date on the development of the biomass into account.

Our study shows that only one third of the cultivation windows are currently used for cultivating cover crops. Thus, the cover crops’ cultivation area could be tripled with additional 2 Mio ha each year. With these additional cover crops, the annual C input could be increased by 12% from 3.68 to 4.13 Mg C ha-1 a-1. Within 50 years, this would result in 35 Tg more SOC in the top 30cm of German croplands which corresponds to 2.6 Tg CO2 equivalents per year. Despite the dry weather conditions, a considerably large increase in SOC can be achieved in the eastern regions of Germany due to a low current cover crop cultivation frequency. However, the limited water availability during the time of cover crop establishment may require undersowing.

We conclude that including cover crops in crop rotations and consequently avoiding bare fallow in winter is a key measure in a climate mitigation strategy for managing cropland soils, and we will discuss the benefits and barriers of growing cover crops in Germany and Europe.
Investigation of European tropospheric ozone trends using multiple satellite records
Authors: Pimlott Matilda , Pope Richard , Chipperfield Martyn , Kerridge Brian , Siddans Richard , Latter Barry
Published: March 2021

Tropospheric ozone is a harmful atmospheric secondary pollutant. It is produced by the oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides (NOx) and sunlight. Tropospheric ozone has been shown to have a negative impact on human health (e.g. acute and chronic respiratory diseases) and a detrimental impact on plant health (i.e. reducing crop yields). Tropospheric ozone is also a short-lived climate forcer. As a secondary pollutant, the complex nature of tropospheric ozone formation highlights the importance of long-term observations needed to monitor and help understand changes in its abundance and spatial distribution.  

Tropospheric ozone has been measured by satellite since the mid-1990s providing a powerful resource, in combination with other observations (e.g. surface, aircraft and ozonesondes), to better understand tropospheric ozone spatial and temporal evolution. However, recent studies e.g. Gaudel et al. (Elem Sci Anth, 6: 39. DOI: https://doi.org/10.1525/elementa.291, 2018), have highlighted substantial inconsistencies in the sign and magnitude of different satellite records both globally and regionally (including Europe). Therefore further study is required to look at these satellite trends in more detail using updated products. It is also important to investigate the causes of these trends to better understand the roles different factors play in affecting European tropospheric ozone abundance and distribution, e.g. precursor gas emissions, meteorology and stratospheric-tropospheric ozone exchange.  

This presentation provides an comprehensive update of European tropospheric and sub-column (~0-6 km) ozone trends from satellite exploiting state-of-the-art records. These include records from the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2), developed by the UK Rutherford Appleton Laboratory (RAL Space), focusing on the recent era (2005-2019).  The trends across both Europe and smaller regions are investigated using a non-linear least squares fit regression model. Modelling studies using the TOMCAT 3-D model will help aid the interpretation of different satellite vertical sensitivities when retrieving ozone in the troposphere on trends and investigate the dominant processes driving them.   
Overview of West Antarctic tectonic evolution from ~500 Ma to the present
Authors: Jordan Tom , Riley Teal , Siddoway Christine
Published: March 2021

West Antarctica developed as the tectonically active margin separating East Antarctica and the Pacific Ocean for almost half a billion years. Its dynamic history of magmatism, continental growth and fragmentation are recorded in sparse outcrops, and revealed by regional geophysical patterns. Compared with East Antarctica, West Antarctica is younger, more tectonically active and has a lower average elevation. We identify three broad physiographic provinces within West Antarctica and present their overlapping and interconnected tectonic and geological history as a framework for future study: 1/ The Weddell Sea region, which lay furthest from the subducting margin, but was most impacted by the Jurassic initiation of Gondwana break-up. 2/ Marie Byrd Land and the West Antarctic rift system which developed as a broad Cretaceous to Cenozoic continental rift system, reworking a former convergent margin. 3/ The Antarctic Peninsula and Thurston Island which preserve an almost complete magmatic arc system. We conclude by briefly discussing the evolution of the West Antarctic system as a whole, and the key questions which need to be addressed in future. One such question is whether West Antarctica is best conceived as an accreted collection of rigid microcontinental blocks (as commonly depicted) or as a plastically deforming and constantly growing melange of continental fragments and juvenile magmatic regions. This distinction is fundamental to understanding the tectonic evolution of young continental lithosphere. Defining the underlying geological template of West Antarctica and constraining its linkages to the dynamics of the overlying ice sheet, which is vulnerable to change due to human activity, is of critical importance.