bluuebunny/crossref_metadata_2025 huggingface dataset:
The hydrological response of the combination between LID and underground integrated pip corridors based on SUSTAIN
Authors: Li Shanshan , Wang Zhaoli , Liu Qing'e
Published: March 2020

With the global climate change and the rapid expansion of urban land use, urban storms and floods have occurred frequently. The state has gradually attached importance to the unified construction of low-impact development facilities (LID) and underground integrated pipe corridors (GL), which makes sponge city both beautiful and practical. In order to study the urban hydrological response of the combination between LID and underground integrated pip corridors (LID_GL), the Yangmei River Basin, a pilot area of ​​Guangzhou's integrated pipe corridors, was taken as an example to evaluate and compare the hydrological response of traditional development, GL, LID, GL_LID scenarios. The results show that:

(1) The traditional development scenario is verified by the measured rainfall of “2018.06.08”. The simulation results are consistent with the areas where are liable to waterlogging under the actual circumstance, which proves that the SWMM model is suitable for the hydrological response evaluation of LID_GL scenario in the Yangmei River Basin.

(2) The SUSTAIN model can realize the optimized layout of LID, but the simulation accuracy needs to be improved. On the contrary, the SWMM model cannot realize the LID optimized layout, but the simulation accuracy of urban hydrological response is high. To Combine their advantages, the LID optimized layout schemes calculated by SUSTAIN model are input into SWMM model for hydrological simulation. The results show that this method can avoid the situation that the evaluation results are irrational due to improper layout of LID.

(3) The overflow reduction in the LID_GL scenario is best, which can exceed 60% under high-return-period rainfall conditions. Its peak outlet flow is lower than GL scenario and the peak appearance time is also delayed.

The above research results can provide reference and theoretical support for the unified construction of LID and underground integrated pip corridors (LID_GL) in the future.
Study on Countermeasures System of Ecological Flow Guarantee in Weihe River Basin
Authors: Zhang Xinhai
Published: March 2020

Ensuring the ecological flow of the Weihe River is a basic requirement for strengthening water resources management and ecological protection and restoration in Weihe River Basin and is of great significance for ensuring the safety of water resources and ecological safety in Weihe River Basin. This study selects three major control cross-sections of Beidao, Linjiacun, and Huaxian for ecological flow protection research. In this paper, the existing results of the main control cross-sections were summarized, the Tennant method and the most withered month average flow method were applied to analyze and calculate the ecological base flow. Then, the flow data from 1980 to 2016 are applied to analyze the degree of ecological flow guarantee. Based on the changes in the Weihe River runoff and the development of water resources, the rationality and accessibility of the ecological flow were demonstrated, and the ecological base flow indicators of Beidao, Linjiacun and Huaxian cross-sections were comprehensively determined to be 2m3/s, 5m3/s, and 12m3/s, respectively. Furthermore, the current status of ecological security in the Weihe River Basin was analyzed in depth. It is clear that there were problems in the Weihe River Basin, such as strong water demand, the high pressure of water uses for life, production and ecology during dry years, difficult guarantee of ecological flow, incomplete ecological flow guarantee working mechanism, etc. Based on the analysis, the suggestions were proposed from the perspectives of enhancing the organization and leadership, intensifying the unified allocation of water resources in the Weihe River, strengthening the capacity of water regime monitoring, establishing an early warning system for ecological flow, strictly controlling water withdrawal, and reinforcing supervision and assessment. Then the countermeasure system of ecological flow guarantee was established.
Impact of Langmuir Turbulence on the Ocean Upper Mixed Layer in a 3D Coupled Regional Model of the South China Sea
Authors: Yu Chengcheng , Song Jingbao , Li Shuang
Published: March 2020

Langmuir turbulence (LT) can have a significant impact on the ocean mixing in the ocean surface boundary layer. In this study, using the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COWAST) modeling system, a 3D wave-current coupled regional model of the South China Sea (SCS) was developed. And the second-moment closure model developed recently by Harcourt, which includes the effects of LT, was introduced into the circulation model to investigate its influence on the coupled models’ performance. Comparisons between the model results with and without LT effects and between the model results and the observations are analyzed. Overall, with the LT effects, the simulated results are more consistent with the observations. When the LT effects are not considered, the mean annual deviation between the model simulated sea surface temperature (SST) and the observed data in the SCS is 1.09℃, as the LT effects introduced, the mean annual SST deviation decrease to -0.06℃ and the deviation almost disappear. Compared with the huge improvement in SST simulation, the introduction of LT has less influence on the simulation of the upper mixing layer depth (MLD). Nevertheless, the model results have also been improved to some extent, with the model performance is improved by 12.7%. Moreover, the eastern and southern parts of the SCS show a more pronounced amelioration than other regions. From the intercomparisons among the experiments, it is also found that the LT exerts more significant impacts on both SST and MLD during spring and summer.
Targeted geoengineering as an ethical response to climate risk
Authors: Moore John
Published: March 2020

IPCC targets 1.5C or 2C global temperature rises relative to pre-industrial as the rises required to prevent significant damage. Politicians have paid lip-service to these with international commitments such as the Paris Accord, but the fact remains that these commitments are not sufficient to meet these targets. Indeed, it is almost impossible to do so. Cooling the earth by stratospheric aerosol injection geoengineering has been proposed as a possible way of avoiding crossing the IPCC 2C threshold. But there are numerous issues related to ethics, equity, and economics when dealing with global control of climate that make such deployment extremely difficult. An alternative would be to tackle the impacts of climate change piecemeal. To that end solutions to cryosphere risks have been proposed (to preserve sea ice, permafrost and ice sheets), and these are very much easier to deal with ethically and from governance perspectives. Furthermore, they are providing much needed hope and opportunities to buy-in to the issue for young people. The opportunities to move the discussion forward by emphasizing the moral opportunities to help the South, unborn generations and other species can be readily grasped by these kinds of interventions.
Estimation of the hourly snowmelt based on the heat balance method using the Japan Meteorological Agency observation data alone and application for analyzing groundwater level fluctuation in a landslide site
Authors: Matsunaga Takamasa , Katsura Shin'ya
Published: March 2020

 The heat balance method has often been used for calculating the snowmelt for the purpose of estimating watershed water resources in the form of snow in winter and analyzing snowmelt runoff. Because the method requires many weather elements, some of which are not observed frequently (e.g., longwave radiation), methods of estimating such less frequently observed weather elements from more frequently observed ones have also been proposed. However, few previous studies have developed a method of estimating the hourly snowmelt based on the heat balance method using the frequently observed weather elements alone and applied for analyzing the hourly groundwater level fluctuation in a landslide site in snow-covered area. In this study, we developed a model of estimating the hourly snowmelt based on the heat balance method using the Japan Meteorological Agency observation data, the most commonly available weather data in Japan, alone, (i.e., temperature, precipitation, wind speed, sunshine duration, atmospheric pressure, and vapor pressure), and applied the model to a past landslide site with deep sliding surface (approximately 20 m) in snow-covered area in Hokkaido, Northern Japan. Moreover, we applied the functional models based on the antecedent precipitation index calculated using (the meltwater and/or rainwater) instead of the rainfall to reproduce the hourly groundwater level fluctuation observed in the site. The results showed good agreement between the observed and calculated snowmelt and groundwater level. The models proposed and used in this study are useful for estimating the hourly snowmelt and analyzing groundwater level fluctuation in a landslide sites in snow-covered area, and should be tested for other landslide sites to further verify the applicability.
Integration of geodetic observations and geological models for investigating the permanent component of land subsidence in the Po Delta (northern Italy)
Authors: Vitagliano Eleonora , Di Maio Rosa , D'Ambrogi Chiara , Calcaterra Domenico , Fiaschi Simone , Floris Mario
Published: March 2020

Defining land subsidence causes is not an easy task, because ground lowering is a complex phenomenon due to the contribution of different physical processes related to natural contest and to anthropic actions. Indeed, such processes, which are characterized by a specific origin and may act in different spatial and temporal intervals, can overlap giving rise to a single surface land deformation, observable through conventional and innovative monitoring techniques (i.e. high-precision levelling, InSAR and GNSS). Of course, discriminating the individual causes is fundamental for reducing environmental and social harms, especially in deltas and coastal areas, where land sinking, coupled with climatic effects, can induce massive flooding. The present work concerns an application of a multi-component and multi-source approach, recently proposed by some of the authors for studying land subsidence in deltas. Such a methodology is aimed at understanding the processes causing both periodic and permanent components of the vertical land movement and at retrieving more accurate subsidence rates. It consists of three steps, respectively involving: a component recognition phase, based on statistical and spectral analyses of geodetic time series; a source (or physical process) selection phase, based on the comparison with data of different nature; a source validation step, where the selected sources are validated through physically-based models. The proposed procedure has been applied to the permanent component of subsidence in the Po Delta (northern Italy), an area historically affected by land subsidence and influenced by climatic changes, where continuous GNSS data and differential InSAR-derived time series were simultaneously acquired from 2012 to 2017. In particular, the exponential relation found between the mean SAR-derived LOS velocity and the thickness of the Late Holocene prograding deposits, pointed out the key role of the sedimentary compaction process with respect to the spatial distribution of the subsidence rates and confirmed the importance, already highlighted by other authors, of the consolidation of the shallower strata. In order to validate the consolidation process and to quantify also the deeper contributions of tectonics- and isostasy-depending mechanisms, 2D geological models have been constructed along two west-east sections across the central part of the Delta. Finally, the computed subsidence rates have been compared with the geodetic velocities estimated in Taglio di Po and Porto Tolle villages (Rovigo, northern Italy), clarifying the contribution of each geological mechanism to the observed delta subsidence.
Shear localization during magma ascent: results from quasi-2D numerical simulations
Authors: Melnik Oleg , Tsvetkova Yulia
Published: March 2020

At large crystal contents magma exhibits non-Newtonian behavior, typically shear thinning due to crystal orientation along streamlines. 1D models widely used for extrusive eruption simulations cannot capture efficiently the complexity of cross-conduit variations of the properties of magmas as they assume parabolic velocity profile and averaged properties of magma. Large aspect ratios of volcanic conduits (length/diameter) makes use of fully 2D numerical models computationally expensive and not reliable because of extremely large cross-conduit variation of parameters.

Here we present results of numerical simulations of a quasi-2D model that accounts for magma crystallization with the release of the latent heat, shear thinning rheology, heat transfer and viscous dissipation. Simulated velocity profile is far from parabolic. Shear layers form initially near the wall of the conduit and migrate towards the interior as magma ascends. Shear heating results in significant increases in temperature of the magma in narrow shear bands. There is a drastic difference between the predictions of 1D and quasi-2D models in terms of pressure-discharge rate relations. Lava dome morphology can be strongly affected by the formation of shear zones inside volcanic conduits during magma ascent.
Recent increase in winter hazy days over Central India
Authors: Kanawade Vijay , Thomas Abin , Sarangi Chandan
Published: March 2020

The Indian subcontinent is greatly vulnerable to air pollution, especially during the dry winter season. Here, we use 15 years (2003-2017) of satellite and model reanalysis datasets over India and adjoining Seas to estimate the trends in the number of days with high aerosol loading (i.e. hazy days) from October to February. The number of days with high aerosol loading in recent years (2013-2017) is increasing at the rate of ~2.6 days/year over Central India, which is surprisingly higher than the more polluted Indo-Gangetic Plain (~1.7 days/year).  Similar increment in absorbing aerosols is also visible in recent years.  As a result, the estimated atmospheric warming over Central India is two-fold higher than that over Indo-Gangetic Plain. This anomalous increase in hazy days over Central India is attributed to a relatively higher increase in biomass burning over this region. The number of days with high aerosol loading in recent years are also higher over the Arabian Seas, which is located downwind to Central India, as compared to the Bay of Bengal. Thus, our findings not only draw attention to deteriorating air quality over Central India but also underlines the significance of enhanced biomass burning activities under recent climate change.
LIFE Nadapta: A regional-scale strategy using soil condition assessment for evaluating climate change vulnerability and adaptation of agriculture in Navarre, Spain
Authors: Virto Inigo , Antón Rodrigo , Arricibita Fco. Javier , Ruiz-Sagaseta Alberto , Enrique Alberto , de Soto Isabel , Orcaray Luis , Zaragüeta Armel
Published: March 2020

The Life Nadapta project (https://lifenadapta.navarra.es/en/inicio) aims to develop a regional-scale integrated strategy for climate change adaptation in the region of Navarre (Spain). This strategy encompasses the most affected economic sectors, including agriculture. Agriculture is highly dependent on climatic conditions, and therefore especially vulnerable to changes in climate. This vulnerability is dependent, among other factors, on soil characteristics and condition. The interaction of this vulnerability with the exposure of agrosystems to climate change impacts (drivers of change) can explain the expected risks associated to these impacts.

Understanding the resilience and possibilities of adaptation of agrosystems requires assessing how they can modulate their vulnerability and/or reduce their exposure. Agricultural management, and in particular, soil organic matter management play a key role in this sense.

In this framework, the project assesses the vulnerability and adaptability of agrosystems in three steps: First, a preliminary diagnosis of soils vulnerability in the territory was conducted, including a division in 12 homogeneous areas and the particular assessment of soil characteristic in each of them. Then, three major strategies of agricultural management aiming to improve the adaptability of agrosystems (namely crop rotations, organic fertilization and conservation agriculture) will be assessed by selecting representative agricultural plots under contrasted management in each of the areas. More than 150 plots will be included in this assessment, that makes a regional network for monitoring. That for, a specific sampling design was developed to effectively reflect the variability and different soil characteristics, and ant the same time, grant homogeneous paired comparisons.  As the three strategies are known to have a potential to increase soil organic C (SOC) stocks, and to modify other soil parameters such as water retention or erodibility, the last phase consists in assessing SOC and other indicators of soil condition, under the light of the projected climate change scenarios and identified impacts in the region.

Preliminary results show differences in vulnerability for the selected areas, and different responses of SOC and other soil indicators to the strategies tested, depending on the natural characteristics of the soils and the historical land-use in the territory.
Seismic imaging of the deep crustal structure beneath Eastern Ghats Mobile Belt (India): Crustal growth in the context of assembly of Rodinia and Gondwana supercontinents
Authors: Singh Arun , Singh Chandrani
Published: March 2020

We present the first high resolution seismic images illuminating the hitherto-elusive crustal architecture beneath the Eastern Ghats Mobile Belt (EGMB) using teleseismic receiver functions. Data were collected using 27 broadband seismic stations operated in a continuous mode covering two distinct seismic profiles (~550 km long) during 2015–2018. Several interesting observations and inferences are made through analysis of the receiver functions such as (a) a very thick crust (>40 km) with oppositely dipping Moho beneath the EGMB and Archean Bastar Craton, (b) EGMB formed from amalgamation of different crustal domains thrust over one another possibly during the Pan-African orogeny, (c) the Archean Bastar Craton crust extends (~75 km) eastward beneath the EGMB, from its surficial geological boundary, (d) there is a sharp contrast in the crustal structure (with ~20 km Moho offset) at the contact between the Rengali Province and Singhbhum Craton which does not support southward growth of the Singhbhum Craton through accretion, (e) anorthosite complexes may possibly be created by rising diapirs channeled through the weak zones in the crust, from the magma chambers developed by melting of frontal portion of the underthrusting lower crust. We report a significant change in the crustal architecture just east of the most elevated topography observed along the profile covering the Bastar Craton and the EGMB. It requires further careful petrological investigations to ascertain the relationship of high elevation and its linkages with the deep crust, forming a separate domain. Our results do not support or discard a Grenvillian age (~1 Ga) docking of the EGMB with Proto-India, though it is preferred to explain the present day crustal features with intense Pan-African (0.5–0.6 Ga) reorganization.
Optimizing COSMO_REA6 reanalysis radiation flux for a high resolution coastal ocean model
Authors: Vodopivec Martin , Ličer Matjaž
Published: March 2020

When modelling coastal areas in high spatial resolution, it is also essential to obtain atmospheric forcing with suitably fine grid. The complex coastline and coastal orography exert strong influence on atmospheric fields, wind in particular, and the east Adriatic coast with numerous islands and coastal mountain ridges is a fine example. We decided to use a high resolution COSMO atmospheric reanalysis for our long term ROMS_AGRIF hindcasts, but in our initial experiments we found out that the atmospheric model significantly underestimates the short wave flux over the Mediterranean Sea, probably due to overestimation of high clouds formation and erroneous sea surface temperature used as a boundary condition. We explore different atmospheric models and different combinations of fluxes - direct, diffuse and clear sky solar radiation and combinations of fluxes from different atmospheric models (eg. ERA5). We compare them with solar irradiance observations at a coastal meteorological station and run year-long simulations to compare model sea surface temperature (SST) with satellite observations obtained from Coprenicus Marine Environment Monitoring Service.
Windows of Opportunity in Decadal Predictions of North Atlantic SST
Authors: Mignot Juliette , Borchert Leonard , Menary Matthew , Swingedouw Didier , Sgubin Giovanni , Yeager Stephen
Published: March 2020

The skill of decadal predictions in the North Atlantic region changed over time in the 20th century. Recent work based on a single model argued that times of high skill – so-called windows of opportunity – could be identified for average North Atlantic SST by knowing the strength of meridional ocean heat transport in the subpolar North Atlantic at the start of a prediction.

Here, we verify these previous findings for the period 1970-2015 in several prediction systems of the Decadal Climate Prediction Project (DCPP) based on models used in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We find windows of opportunity for decadal predictions of average North Atlantic SST in all examined prediction systems. The timing of these windows of opportunity generally agrees with the published estimate, indicating their robustness around the end of the twentieth century.

Decadal SST prediction skill in the North Atlantic Subpolar Gyre (SPG) shows much less consistent windows of opportunity between prediction systems than average North Atlantic SST. We explore model differences that explain these inconsistencies, discussing the spatial and temporal representation of North Atlantic ocean circulation and heat redistribution in the different prediction systems. We then show that connecting windows of opportunity to observable climatic variables such as sea surface height anomalies in the subpolar North Atlantic can constrain future skill estimates.
Estimation of Extreme Rainfall in South Africa and Development of Methods to Account for Non-stationary Climate Data
Authors: Johnson Katelyn , Smithers Jeff
Published: March 2020

The estimation of design rainfalls and design floods are required by engineers and hydrologists to design and quantify the risk of failure of hydraulic structures. Extreme design rainfall quantities such as high-return period rainfalls and the probable maximum precipitation (PMP) are needed to design high-hazard hydraulic structures. In South Africa, previous design rainfall estimates have been produced up to the 200 year return period. PMP estimates were last determined nearly 50 years ago based on only 30 years of data. Most studies on extreme rainfall reported are based on frequency analysis assuming stationary conditions. Previous studies in South Africa have assumed a stationary climate. However, the assumption of a stationary climate in rainfall and flood frequency analysis has been challenged owing to evidence of climate change. Recent literature indicates that the magnitude and frequency of extreme rainfall events has been changing and this is likely to continue in future. Hence, methods to account for trends in extreme rainfall events in a changing environment need to be developed. In addition, the concept of PMP, particularly as used for the design and safety evaluation of large dams in South Africa, is being challenged with the recommendation that high-return period design rainfalls be used in these assessments. The aims of this study are: (i) to estimate extreme design rainfall values, with a focus on return periods greater than 200 years, (ii) to update PMP estimates using updated data and modernised methods, and (iii) to account for non-stationary climate data in the estimation of these extreme rainfall events in South Africa. Frequency analysis using LH-moments, which more accurately fit the upper tail of distributions, have been used to estimate high-return period design rainfalls. Regular L-moments are shown to overestimate the extreme rainfall quantities when compared to LH-moments by giving undue favour to outliers. PMP estimates have been determined using a storm maximisation and transposition approach. Radial Basis Functions (RFBs) have been used to transpose PMP estimates to ungauged locations, producing PMPs for the entire country. Approximately 80 % of the new PMPs are greater than the previous estimates. This is probably due to the many limitations of the old approach and differences used in the new approach, indicating that the new approach undertaken in this study may provide improved estimates. The PMP represents the upper limit of extreme rainfall, however, comparisons of high-return period rainfalls to the PMP show that the PMP is sometimes exceeded by the high-return period rainfalls. To develop methods to estimate extreme design rainfall events in a non-stationary climate, this study explores the impacts of climate drivers, such as the Southern Oscillation Index (SOI), and changes in atmospheric variables, such as dew point temperature, on high-return period rainfalls and the PMP.
The relationship between ionospheric parameters and solar proxies is changing – when?
Authors: Laštovička Jan
Published: March 2020

The relationship between ionospheric parameters and solar activity proxies has broadly been assumed to be stable. However, using data of foF2 from three European stations and foE from two European stations we show that this assumption is not correct. In more recent years the dependence of ionospheric parameters on solar proxies is steeper than in the past. The change is between 1994 and 1997 for foF2 and after 2000 for foE. Also the relationships among solar proxies have changed, which might indicate some solar changes perhaps responsible for the observed changes of the relationship between ionospheric parameters and solar proxies with implications to trend and climatological studies, and modeling.

 
Mineralogical composition of solonetzic complex with unexpressed micro-relief in the northern part of the caspian lowland.
Authors: Churilin Nikita , Lebedeva Marina , Varlamov Evgheni
Published: March 2020

Chestnut soils are an obligatory component of solonetz complexes in the northern part of the Caspian lowland, differ from solonetzes by the morphological properties of the horizons, although these soils are usually located at a distance of several meters.

For the chestnut soil we can see the following vegetation: forbs-fescue-feather association with spirea, sometimes with a thin moss cover. Above the solonetz dominates Kochia prostrata and Artemisia pauciflora with Myosúrus sp. and rare Poa sp. curtains.

The aim of the study is to identify the mineralogical composition of clay fraction (<1 μm) of chestnut soil and to compare it with the mineralogical composition of the solonetz in the area with unexpressed microrelief.

To separate soil fractions <1 μm samples were rubbed into a thick paste and sedimented. Oriented preparations of fractions were examined by XRD method.

The balance of the mineral phases of clay in soils and parent rocks is the same - mixed-layered minerals prevail over illite. An exception is only the upper horizons of the compared soils, in which the content of illite prevails over mixed-layer minerals. In this case, the thickness of the surface horizons differs more significantly (5 times) than the difference in the content of illite in the clay fraction of the solonetz in SEL (0-5 cm) horizon. This soils are also have certain features of similarity in the crystallochemical shape: the imperfection of the kaolinite structure and the superdispersed shape of the mixed-layer phase at the surface horizons, as well as the appearance of individual smectite and chlorite packets in the mixed-layer phase in the lower horizons (BC and C).

The work was supported by RFBR 18-016-00129-а.
Which Processes could define Temperature Limits on the Outer Surface of a Container in a Disposal Facility ?
Authors: Bracke Guido , Hartwig-Thurat Eva , Larue Jürgen , Meleshyn Artur , Weyand Torben , Kock Ingo
Published: March 2020

When the recommencement of the search for and selection of a site for a disposal facility for HLRW in Germany was stipulated by the Site Selection Act (StandAG 2017) in 2017, a precautionary temperature limit of 100 °C on the outer surface of the containers with high-level radioactive waste in the disposal facility section was set. This precautionary temperature limit shall be applied in preliminary safety analyses provided that the “maximum physically possible temperatures” in the respective host rocks have not yet been determined due to pending research. Therefore, this issue is addressed and discussed in this paper, contributing to “pending research” by a review of the literature.

This presentation briefly discusses a few examples of thermohydraulical, mechanical, chemical and biological processes in a disposal facility, because temperature limits are derived based on safety impacts regarding THMCB-processes. The temperature-dependent processes have been extracted from databases for features, events and processes (FEP-databases). Furthermore, it is dicussed if the feasibility to retrieve and recover HLRW is hampered at high temperatures.

It is concluded that a design temperature concerning single components of a disposal facility for the preservation of their features can be derived when a safety concept is established. However, the interactions of all relevant processes in a disposal concept must be considered to determine a specific temperature limit for the outer surface of the containers. Therefore, applicable temperature limits may vary for particular safety and disposal concepts in the following host rocks: rock salt, clay stone and crystalline rock.

Technical solutions for retrieval and design options for recovery seem to be viable up to temperatures of 200 °C with different, sometimes severe, downsides according to expert judgement.

It is summarized that emperature limits regarding the outer surface of the containers can be derived specifically for each safety concept and design of the disposal facility in a host rock. General temperature limits without reference to specific safety concepts or the particular design of the disposal facility may narrow down the possibilities for optimisation of the disposal facility and could adversely affect the site selection process in finding the best suitable site.
Computational Fluid Dynamics modelling of sedimentation on Mars
Authors: Kuhn Nikolaus J. , Trudu Federica
Published: March 2020

Gravity affects sedimentation of particles suspended in water and gases in two ways: directly by the gravitational force that pulls a particle towards the surface and indirectly by the flow conditions of water or gas around the particles. The latter create a drag which is affected by the settling velocity. Consequently, drag coefficients observed on Earth sand-sized particles cannot be used on Mars because they are likely to overestimate the drag generated by the turbulent flow around the particle on Earth may shift into a more laminar state that generates lower drag. The effect of gravity on settling velocity is not linearly related to particle size, which may affect the sorting of the sand grains deposited from running water.  Experiments carried out during parabolic flights at reduced gravity indicate that the potential error in particle settling and sorting is significant, i.e. leading to wrong interpretations of the flow velocities at the time of deposition. This in turn has implications for reconstruction of Martian environmental conditions from rock textures determined from close-up imagery. This study uses computational fluid dynamics (CFD) modelling to independently assess the effect of gravity on sediment settling velocities and sediment sorting. The CFD modelling also offers a wide capability for reconstruction sedimentation on Mars and thus supports the reconstruction of it’s environmental past, as well as the search for traces of life. 
Surface wind flow modelling on Mars using Computational Fluid Dynamics
Authors: Love Richard , Jackson Derek. W. T. , Cooper J. Andrew G. , Avouac Jean-Philippe , Smyth Thomas A. G. , Michaels Timothy I.
Published: March 2020

Wind flows on Mars are the dominant contemporary force driving sediment transport and associated morphological change on the planet’s dune fields. To fully understand the atmospheric – surface interactions occurring on the dunes, investigations need to be conducted at appropriate length scales (at or below that of any landform features being examined).

The spatial resolution of Martian Global Circulation Models (GCMs) is too low to adequately understand atmospheric-surface processes. Nevertheless, they can be utilised to establish initial state and boundary conditions for finer-scale simulations. Mesoscale atmospheric models have been used before to understand forcing and modification of entire dune fields. However, their resolution is still too coarse to fully understand interactions between the boundary layer and the surface. This study aims to examine and improve our understanding of local-scale processes using microscale (e.g., 1.5m cell spacing) airflow modelling to better investigate localised topographic effects on wind velocity and associated aeolian geomorphology.

Toward these aims, this study will simulate microscale wind flow using computational fluid dynamics software (OpenFOAM) at a series of sites containing a variety of topographies and wind regimes. A Mars GCM will provide input for baseline mesoscale modelling runs, the output of which will then be used as input for microscale airflow modelling. The sites used for the study will have excellent orbital, or preferentially, in situ data coverage. Detailed HiRISE imagery will provide high-resolution Digital Terrain Models (DTMs) which will be used by the OpenFOAM simulations. Results from model simulations will be evaluated/validated using both in situ data and geomorphic analysis of imagery.
Permeability models for carbonate fault cores
Authors: Agosta Fabrizio
Published: March 2020

The present contribution focuses on carbonates fault cores exposed in central and southern Italy, which crosscut Mesozoic limestones and dolostones, pertain to 10’s of m- to 100’s of m-throw extensional fault zones, and include two main domains named as inner and outer fault cores, respectively. The inner fault cores are made up of main slip surfaces (MSS), matrix-supported cataclasites, and fault breccia. Cement-supported cataclasites, if present in the limestone-hosted fault cores, localize around the MSS. The outer fault cores mainly include grain-supported cataclasites, subsidiary slip surfaces, and lithons of fragmented host rocks. In order to assess the fluid flow properties of the carbonate fault cores, the results of microstructural, petrophysical, and ultrasonic studies are first presented, and then discussed in terms of pore type, geometry, textural anisotropy, and poro-perm relationships. Overall, the documented pore distribution is mainly function of both deformation micro-mechanisms and diagenetic processes, which took place in the carbonate fault cores during faulting and fault rock exhumation from depth. In the limestone-hosted fault cores, the experimental results show that the cross-fault fluid flow properties are affected by the the irregular geometry of the cement fronts. These fronts, which depart from the MSS, are due to calcite precipitation in vadose environments from meteoric-derived fault fluids. At depths of about 1 km, these fluids merge with the local freshwater aquifers, and cement the whole fault cores. Overall, these fault cores include a stiff pore networks, and are thought to behave like a granular medium. There, it is proposed that the cross-fault permeability can be computed by applying the Kozeny-Carmen correlation. For any given value of effective porosity, the value of permeability is therefore proportional to the average value of the pore throat, which characterize the aperture of capillary tubes with a geometrical tortuosity of ca. 2.5. On the contrary, the dolostone-hosted fault cores include a soft pore network made up of elongated pores, and are thought to behave like an elastic cracked medium. Accordingly, it is proposed that the cross-fault permeability can be computed by following percolation theory by considering the values of dynamic elastic moduli measured during ultrasonic tests at Pc=30 MPa, and almost isotropic fracture networks. Results of this work could be helpful during appraisal and development operations of hydrocarbon reservoirs, for freshwater aquifer protection, and activities of CO2 storage in depleted carbonate reservoirs.
Performance analysis of regional landslide early warning based on soil moisture simulations
Authors: Wicki Adrian , Stähli Manfred
Published: March 2020

In mountainous regions, rainfall-triggered landslides pose a serious risk to people and infrastructure, particularly due to the short time interval between activation and failure and their widespread occurrence. Landslide early warning systems (LEWS) have demonstrated to be a valuable tool to inform decision makers about the imminent landslide danger and to move people or goods at risk to safety. While most operational LEWS are based on empirically derived rainfall exceedance thresholds, recent studies have demonstrated an improvement of the forecast quality after the inclusion of in-situ soil moisture measurements.

The use of in-situ soil moisture sensors bears specific limitations, such as the sensitivity to local conditions, the disturbance of the soil profile during installation, and potential data quality issues and inhomogeneity of long-term measurements. Further, the installation and operation of monitoring networks is laborious and costly. In this respect, making use of modelled soil moisture could efficiently increase information density, and it would further allow to forecast soil moisture dynamics. On the other hand, numerical simulations are restricted by assumptions and simplifications related to the soil hydraulic properties and the water transfer in the soil profile. Ultimately, the question arises how reliable and representative landslide early warnings based on soil moisture simulations are compared to warnings based on measurements.

To answer this, we applied a state-of-the-art one-dimensional heat and mass transfer model (CoupModel, Jansson 2012) to generate time series of soil water content at 35 sites in Switzerland. The same sites and time period (2008-2018) were used in a previous study to compare the temporal variability of in-situ measured soil moisture to the regional landslide activity (currently under review in Landslides). The same statistical framework for soil moisture dynamics analysis, landslide probability modelling and landslide early warning performance analysis was applied to the modelled and the measured soil moisture time series. This allowed to directly compare the forecast skill of modelling-based with measurements-based landslide early warning.

In this contribution, we will highlight three steps of model applications: First, a straight-forward simulation to all 35 sites without site-specific calibration and using reference soil layering only, to assess the forecast skill as if no prior measurements were available. Second, a model simulation after calibration at each site using the existing soil moisture time series and information on the soil texture to assess the benefit of a thorough calibration process on the forecast skill. Finally, an application of the model to additional sites in Switzerland where no soil moisture measurements are available to assess the effect of increasing the soil moisture information density on the overall forecast skill.
A parameterization of local and remote tidal mixing
Authors: de Lavergne Casimir , Vic Clément , Madec Gurvan , Roquet Fabien , Waterhouse Amy , Whalen Caitlin , Cuypers Yannis , Bouruet-Aubertot Pascale , Hibiya Toshiyuki
Published: March 2020

Vertical mixing is often regarded as the Achilles’ heel of ocean models. In particular, few models include a comprehensive and energy-constrained parameterization of mixing by internal ocean tides. Here, we present an energy-conserving mixing scheme which accounts for the local breaking of high-mode internal tides and the distant dissipation of low-mode internal tides. The scheme relies on four static two-dimensional maps of internal tide dissipation, constructed using mode-by-mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three-dimensional map of dissipation which compares well with available microstructure observations and with upper-ocean finestructure mixing estimates. Implemented in the NEMO global ocean model, the scheme improves the representation of deep water-mass transformation and obviates the need for a constant background diffusivity.
Precise Galileo orbit determination using combined GNSS and SLR observations
Authors: Bury Grzegorz , Sośnica Krzysztof , Zajdel Radosław , Strugarek Dariusz
Published: March 2020

The European navigation system Galileo is on its final stretch to become a fully operational capability (FOC) Global Navigation Satellite System (GNSS). The current constellation consists of 24 healthy satellites decomposed into three Medium Earth Orbits and since late 2016 is considered as an operational system. So far, the official Galileo orbits are provided by the European Space Agency and in the frame of the International GNSS Service (IGS) Multi-GNSS pilot project (MGEX) whose one of the goals is to develop orbit determination strategies for all new emerging navigation satellite systems.

All the Galileo satellites are equipped with Laser Retroreflector Arrays (LRA) for Satellite Laser Ranging (SLR). As a result, a number of Galileo satellites is tracked by laser stations of the International Laser Ranging Service (ILRS). SLR measurements to GNSS, such as Galileo, comprise a valuable tool for the validation of the orbit products as well as for an independent orbit solution based solely on laser ranging data. However, the SLR data may be used together along with the GNSS observations for the determination of the combined GNSS orbit using the two independent space techniques co-located onboard the Galileo satellites. The Galileo orbit determination strategies, as well as the usage of laser ranging to the navigation satellites, is crucial, especially in the light of the discussion concerning possible usability of the Galileo observation in the future realizations of the International Terrestrial Reference Frames.    

In this study, we present results from the precise Galileo orbit determination using the combined GNSS data transmitted by the Galileo satellites and the range measurements performed by the ILRS stations. We test different weighting strategies for GNSS and SLR observations. We test the formal errors of the Keplerian elements which significantly decrease when we apply the same weights for SLR  and GNSS data. However, in such a manner, we deteriorate the internal consistency of the solution, i.e., the orbit misclosures.  

For the solution with optimal weighting strategy, we present results of the quality of Galileo orbit predictions based on the combined solutions, as well as the SLR residuals. The combined GNSS+SLR solution seems to be especially favorable for the Galileo In-Orbit Validation (IOV) satellites, for which the standard deviation (STD) of the SLR residuals decreases by 13% as compared to the microwave solutions, whereas for the Galileo-FOC satellite the improvement of the STD of SLR residuals is at the level of 9%. Finally, we test the impact of adding SLR observations to the LAGEOS satellites which stabilizes the GNSS solutions, especially in terms of the realization of terrestrial reference frame origin. 
Total Column Water Vapour Retrieval from S-5P/TROPOMI in the Visible Blue Spectral Range
Authors: Borger Christian , Beirle Steffen , Dörner Steffen , Sihler Holger , Wagner Thomas
Published: March 2020

Atmospheric water plays a key role for the Earth’s energy budget and temperature distribution via radiative effects (clouds and vapour) and latent heat transport. Thus, the distribution and transport of water vapour are closely linked to atmospheric dynamics on different spatio-temporal scales. In this context, global monitoring of the water vapour distribution is essential for numerical weather prediction, climate modeling and a better understanding of climate feedbacks.

Here, we present a total column water vapour (TCWV) retrieval using the absorption structures of water vapour in the visible blue spectral range. The retrieval consists of the common two-step DOAS approach: first the spectral analysis is performed within a linearized scheme. Then, the retrieved slant column densities are converted to vertical column densities (VCDs) using an iterative scheme for the water vapour a priori profile shape which is based on an empirical parameterization of the water vapour scale height.  

We apply this novel retrieval to measurements of the TROPOspheric Monitoring Instrument (TROPOMI) onboard ESA‘s Sentinel-5P satellite and compare our retrieved H2O VCDs to a variety of different reference data sets. Furthermore we present a detailed characterization of this retrieval including theoretical error estimations for different observation conditions. In addition we investigate the impact of different input data sets (e.g. surface albedo) on the retrieved H2O VCDs.  