bluuebunny/crossref_metadata_2025 huggingface dataset:
Postprocessing of precipitation forecasts over India with Quantile Mapping  and Ensemble Model Output Statistics
Authors: Widmann Martin , Angus Michael , Orr Andrew , Leckebusch Gregor
Published: March 2022

Accurate predictions of heavy precipitation in India are vital for impact-orientated forecasting, and an essential requirement for mitigating the impact of damaging flood events. Operational forecasts from non-convection-permitting models can have large biases in the intensities of heavy precipitation, and while convection-permitting models can perform better, their operational use over large areas is not yet feasible. Statistical postprocessing can reduce these biases for relatively little computational cost, but few studies have focused on postprocessing forecasts of monsoonal rainfall.

As part of the UK Weather and Climate Science for Service Partnership India (WCSSP India), the HEavy Precipitation Forecast Postprocessing over India (HEPPI) project has evaluated and compared two popular postprocessing methods: Univariate Quantile Mapping (UQM) and Ensemble Model Output Statistics (EMOS). The project focuses on the suitability of the methods for postprocessing heavy rainfall in India. Both methods are applied to daily precipitation in the National Centre for Medium Range Weather Forecasting (NCMWF) 12km forecast for the 2018 and 2019 monsoon seasons. The evaluation is based on day 1 forecasts and fitting the methods individually for each location.

UQM leads by construction to precipitation distributions close to the observed ones, while EMOS optimises the spread of the postprocessed ensemble without guaranteeing realistic rainfall distributions, and it is not a priori clear which method is better suited for practical applications. The methods are therefore compared with respect to several aspects: local distributions, representation of temporal variability using the Continuous Ranked Probability Score, ensemble spread using Rank Histograms, and exceedance of heavy precipitation thresholds using Brier Scores, Reliability Diagrams, and Receiver Operating Characteristics curves.

EMOS performs not only best, as expected, with respect to correcting under- or overdispersive ensembles, but also with respect to scores for temporal variability, both for the whole range of rainfall values and specifically for heavy rainfall. UQM performs best, as expected, with respect to the local precipitation distributions. The ROC results are inconclusive and location dependent, although both postprocessing methods consistently outperform the raw forecast. These findings are independent of the choice of gridded precipitation data sets used for model fitting and validation.

We recommend EMOS for operational application, as from a user perspective a good performance in forecasting values at a given time, in particular heavy precipitation events, can be expected to be more important than achieving a close match between the forecasted and observed local precipitation distributions.

 
Repeated vertical relative gravity measurements in a well shaft for monitoring water storage changes in the vadose zone
Authors: Reich Marvin , Schröder Stephan , Morgner Markus , Günther Knut , Thoss Heiko , Güntner Andreas
Published: March 2022

The vadose zone plays a key-role for a comprehensive understanding of hydrological states and processes at the interfaces of atmosphere, soil, vegetation and groundwater. Yet it is the most difficult hydrological compartment to observe water storage and fluxes due to limited accessibility and high heterogeneity. Terrestrial gravimetry represents a potentially useful monitoring method for this compartment. Its non-invasive and integrative nature provides many advantages compared to traditional hydrological field methods. Nevertheless, these benefits go along with some methodological downsides: vadose zone water storage changes, for instance, can only be disentangled from integrative measurements if all undesired signal components are known. This can be a challenge in particular for observations with a single gravimeter. However, using two gravimeters may open up new possibilities as the undesired signal components may cancel out when calculating the differences of the gravity observations of both devices. The latter approach was applied in the presented study.

We carried out monthly relative gravity campaigns in the TERENO Observatory (Mueritz National Park, North-East Germany) using 2 Scintrex CG-6 gravimeters (#58, #69). On this site, we have an iGrav (#33) continuously operating since end of 2017. In May of 2019 we started with the monthly campaigns in an about 170 years old water well shaft, located at a distance of about 50 m from the iGrav. This well shaft has a diameter of roughly 2 m and a total depth of 13 m. The groundwater table is one to two meters below the well bottom and continuously monitored. During the campaigns in each month, we performed repeated gravity measurements on 3 pillars: one next to the iGrav, one next to the well shaft on the terrain surface and one on the bottom of the well shaft. This monthly data is compared and chronologically connected to the continuous recordings of the iGrav. Differences of the CG-6 gravity measurements between top and bottom of the well provide a unique dataset for describing the water storage variations in the vadose zone of 13 m thickness. Additionally, we set these observations into the context of meteorological and near-surface soil moisture time series monitored at the site.
Influence of landscape transience on plant biodiversity patterns in the Hengduan Mountains, China
Authors: Gelwick Katrina , Chang Yaquan , Willett Sean , Pellissier Loïc , Zimmermann Niklaus , Wang Zhiheng
Published: March 2022

Mountainous regions are some of the most biologically diverse places on Earth and have exceptionally high rates of endemism. Global biodiversity studies indicate that mountain biodiversity is only partially controlled by global climate drivers and is primarily the result of topographic relief, which amplifies habitat complexity by generating temperature and precipitation gradients. However, climate and relief alone do not fully explain observed patterns of species richness in mountainous regions.

Here, we investigate the plant diversity of the Hengduan Mountains of southwest China, the main biodiversity hotspot outside the tropics, to demonstrate that the generation of this hotspot goes beyond habitat complexity. We mapped species richness patterns for seed plants across the entire Hengduan region and compared them to geomorphic characteristics of the landscape calculated using standard methods of digital topographic (DEM) analysis, including elevation and local relief (5 km radius). As we hypothesized, there is a strong, positive correlation between local relief and species richness generally. We also find large spatial anomalies among different families that may be fingerprints of older geologic processes. We hypothesize that other drivers, such as glacier extent, tectonic faults, and river capture, may explain regions of exceptionally high (resp. low) species richness.

To understand which geological events drove seed plant diversification in the Hengduan Mountains, we developed a generalized linear correlation model to determine the component of species richness explained by climate variables. We removed the component of species richness corresponding to contemporary climate and mapped the residuals to determine where climate underpredicts species richness. We correlated this spatial relationship to known geologic events, based on published thermochronological studies, fault displacement history, and glaciations. In particular, this allows the differentiation between diversification in response to late Quaternary climate change and older, tectono-geomorphic events. We examine patterns across different plant families (from lowland to alpine species) and observe similar adaptive patterns in response to landscape transience.
Observations of Blue Corona Discharges in Thunderclouds
Authors: Husbjerg Lasse , Neubert Torsten , Chanrion Olivier , Dimitriadou Krystallia , Stendel Martin , Kaas Eigil , Østgaard Nikolai , Reglero Victor
Published: March 2022

Blue electric streamer discharges in the upper reaches of thunderclouds are observed as flashes in the second positive band of molecular nitrogen at 337.0 nm (blue) with faint emissions from atomic oxygen at 777.4 nm (red), a dominant line of lightning leaders. Using 2.5 years of measurements by the Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station (ISS), we find that their rise time distribution suggests two distinct categories. One includes those with fast rise times less than 30 mus that are relatively unaffected by cloud scattering and emanate from within ~2 km of the cloud tops, and the other those with longer rise times that come from deeper within the clouds. Satellite measurements show that the clouds with blue discharges have an average cloud top temperature ~200 K compared to ~210 K for those of normal lightning, suggesting that blue discharges occur in clouds that reach near the tropopause. The average convective available potential energy (CAPE) determined from ERA5 reanalysis data is ~1550 J/kg for the shallow events and ~1290 J/kg for the deeper events, compared to ~1010 J/kg for regular lightning, suggesting that the discharges favour strong convective environments. This is further indicated by the geographical distribution of blue discharges which show that they occur mainly near mountain ridges or coastlines known for their strongly convective environments.
A new approach for flood risk estimation integrating remote sensing and in-situ data
Authors: Roseto Rodolfo , Capolongo Domenico , Dellino Pierfrancesco
Published: March 2022

A lot of different methods are used to estimate flood risk worldwide. The method that performs better depends on the catchment features and dimension, data time resolution and availability and uncertainty level required. Remote sensing approaches are more and more common, but because of the limited periods covered by time series derived by this new methodology, in-situ data integration is still required. A new methodology is proposed, based on a case-study of different reaches of Basento river, Basilicata (Southern Italy). Starting from hourly rainfall time series (covering not less than 20 years), for each pluviometric station taken into account into the catchment area, Intensity-Duration-Frequency (IDF) curves are computed (fitting a power law), in order to calculate the rainfall maximum at a certain percentile (typically 90° or 95° percentile are used) during the concentration time. Thiessen polygon method is used to divide the catchment area into smaller areas, each one corresponding to a pluviometric station, with the purpose of calculating weighted  rainfall values for each station area. A Digital Terrain Model is used to extract multiple cross sections of the river-bed, spanning different morphologies, from braided to meandering channels. For each cross section, starting from bankful level, it is possible to estimate diverse hydraulic parameters such as river stage, hydraulic radius, section’s surface area (using image analysis) and the mean velocity of the current, using the logarithmic law profile of the turbulent flow. Sediment size analysis is carried out as to estimate the river bed roughness for each cross section. The mean velocity value V can be used to estimate the concentration time t=L/V, where L is equal to the distance between the cross section and the hydraulically further point into the catchment area. The concentration time value t is used into the equation of the IDF curves, in order to link the corresponding rainfall height to the river stage reached at the cross section, eventually to estimate the rainfall value that, if exceeded, can cause flood. A FLO-2D model has been then used to run simulations with the aim to detect flood-prone areas, finding an overall good matching between the values of current mean velocity, discharge and river stage estimated in the cross sections.
The effect of soil structure variability on mixing-limited reactions in the rhizosphere
Authors: Diamantopoulos Efstathios , Vincent Henri Christopher
Published: March 2022

Soils are characterized by structural components on multiple spatial scales, originating from soil formation processes, soil-plant interactions, microbial activity and management operations. This leads to local heterogeneities for almost all measurements of physical, chemical and biological state variables. As a result, biochemical reactions are highly variable in space and in time, since they are mainly allowed/controlled by mixing processes bringing together reactants in soils, e.g., nutrients to the vicinity of enzyme or biomass. Studying biochemical reaction in real-world soil-plant-atmosphere systems is very difficult and the true underlying structures can never be absolutely known. For this, it is appealing to employ synthetic experiments to examine how spatial heterogeneity of soils affects the biochemical reactions under realistic boundary conditions. In this work, we present a theoretical approach to assess how the spatial variability of soil structure at the pedon scale affects macroscopic reaction rates. In the new approach, we utilize a reactive Lagrangian algorithm for explicitly modelling chemical reactions in the unsaturated zone under different forcings. The results show that apparent reaction rates are a function of the assumed heterogeneity and of the boundary conditions. We illustrate that the use of average macroscopic reaction rates, that are widely used in many agriculture, environmental and geoengineering models is at least questionable.
Paleostress and paleoburial history of a post-rift, supra-salt, carbonate reservoir offshore Congo (Atlantic): Insights from calcite twinning and stylolite roughness paleopiezometry.
Authors: Zeboudj Anies , Bah Boubacar , Lacombe Olivier , Beaudoin Nicolas E. , Gout Claude , Godeau Nicolas , Girard Jean-Pierre
Published: March 2022

Our understanding of the temporal variation of past stress in the crust is usually pictured in relation to tectonic contexts, where it helps decipher the evolution of deformation of rocks at different scales. The paucity of paleostress reconstructions in passive margins makes the knowledge of the origin of stress and of its evolution very incomplete, especially in poorly accessible offshore parts. Moreover, in salt-rich passive margins like the offshore Congo margin, one may question whether the state of stress in supra-salt formations is mainly controlled by salt tectonics, since the salt usually acts as a decoupling level that prevents the transmission and record of far-field crustal stresses. This study focuses on the analysis of an offshore wellbore core of the Albian, post-rift carbonates of the Sendji Fm that directly overlies the salt of the Aptian Loeme Fm in the Lower Congo Basin. Paleopiezometry based on stylolite roughness and mechanical twins in calcite was combined with fracture analysis, laser U-Pb dating of calcite cement, and burial modeling to unravel the tectonic and burial evolution of the Sendji Fm over time. The results of bedding-parallel stylolite roughness inversion constrain the range of depth over which the Sendji Fm strata deformed under a vertical principal stress s1 to 650-2800 m (median ~1100m). Projection of this depth range onto the Sendji burial model derived from TemisFlow™ basin modelling indicates that pressure solution was active from 105 to 12 Ma. Inversion of calcite mechanical twins measured within the early diagenetic cement (U-Pb age = 100 +/- 1Ma) yields two main states of stress: (1) an extensional stress regime with a horizontal σ3 trending ~E-W associated with sub-perpendicular N-S compression, and (2) a strike-slip stress regime with a horizontal σ1 trending ~E-W (changing from pure E-W compression to N-S extension through stress permutations). We interpret the former state of stress as local and related to the complex geometric interactions between moving halokinetic normal faults, while the latter presumably reflects the push effect of the Atlantic ridge, which prevailed from 12 Ma until present-day. Our results highlight that the stress history of the studied part of the offshore Lower Congo Basin passive margin has first been mainly dominated by burial and local normal faulting related to late Cretaceous to Miocene post-rift salt tectonics, then by a regional stress presumably originated from the far-field ridge push from ~12Ma onwards, which would indicate some mechanical re-coupling between the crust and the sedimentary cover during the Miocene.

Keywords: stress, paleopiezometry, calcite twins, stylolites, passive margin, salt.
Identifying patterns of teleconnections, a curvature-based network analysis
Authors: Schlör Jakob , Strnad Felix M. , Fröhlich Christian , Goswami Bedartha
Published: March 2022

Representing spatio-temporal climate variables as complex networks allows uncovering nontrivial structure in the data. Although various tools for detecting communities in climate networks have been used to group nodes (spatial locations) with similar climatic conditions, we are often interested in identifying important links between communities. Of particular interest are methods to detect teleconnections, i.e. links over large spatial distances mitigated by atmospheric processes.

We propose to use a recently developed network measure based on Ricci-curvature to visualize teleconnections in climate networks. Ricci-curvature allows to distinguish between- and within-community links in networks. Applied to networks constructed from surface temperature anomalies we show that Ricci-curvature separates spatial scales. We use Ricci-curvature to study differences in global teleconnection patterns of different types of El Niño events, namely the Eastern Pacific (EP) and Central Pacific (CP) types. Our method reveals a global picture of teleconnection patterns, showing confinement of teleconnections to the tropics under EP conditions but showing teleconnections to the tropics, Northern and Southern Hemisphere under CP conditions. The obtained teleconnections corroborate previously reported impacts of EP and CP.
Our results suggest that Ricci-curvature is a promising visual-analytics-tool to study the topology of climate systems with potential applications across observational and model data.
Drivers of Antarctic sea-ice advance date
Authors: Himmich Kenza , Vancoppenolle Martin , Madec Gurvan , Sallee Jean-Baptiste , De Lavergne Casimir , Lebrun Marion , Holland Paul
Published: March 2022

Sea-ice advance is a key moment to the Antarctic climate and ecosystem. Over the last 4 decades, sea-ice advance has been occurring earlier in the Weddell and Ross Seas and later west of the Antarctic Peninsula and in the Amundsen Sea. However, not much is known on the drivers of the observed changes nor on the physical processes determining the date of advance in the Southern Ocean. To progress understanding, we investigate the respective roles of ocean-sea ice processes in controlling the timing of sea-ice advance using observational and reanalysis data. Based on the satellite-based sea-ice concentration budget at the time of advance, we identify two regions with distinct processes. In the outermost ice-covered region, a few degrees of latitude within the winter ice-edge, no ice growth is observed and the ice advance date can only occur by transport of ice from higher latitudes. This is consistent with above freezing reanalysis sea surface temperature (SST) at the time of sea-ice advance. Elsewhere in the seasonal ice zone, ice import is a minor contributor to the sea-ice concentration budget hence sea-ice advance must be due to freezing only. In situ hydrographic observations show that the date of advance is more strongly linked to the seasonal maximum of the mixed layer heat content (MLH) than to the seasonal maximum SST — which reflects that the need for the full mixed layer to approach freezing before sea ice can appear. The relationship is stronger in regions with no contribution of sea-ice transport. Based on these considerations, we suggest that upper ocean hydrographic properties and sea ice drift are key features to determine the timing of sea-ice advance.
Electron Dynamics in a Chorus Wave Field Generated from Particle-in-Cell Simulations
Authors: An Zeyu , Wu Yifan , Tao Xin
Published: March 2022

How to properly describe resonant interactions between electrons and quasi-coherent chorus waves is still an open question. Previous studies have progressed from modeling chorus as a single wave to considering effects such as amplitude modulation or phase decoherence in wave particle resonance. However, incorporating realistic features of chorus waves in test particle calculations has always been a challenging but critically important step to evaluate their nonlinear effects. In this work, we use a chorus wave packet generated by a particle-in-cell simulation in test-particle simulations. The used chorus wave naturally has features including amplitude modulation, phase decoherence and dynamic evolution during propagation. Our results suggest that, while being latitudinal dependent, realistic features of chorus generally lead to significant suppression of nonlinear effects. This result should be important to understand phase space transport of electrons due to interactions with chorus waves.
Spatio-temporal communities in networks of extreme rainfall events of the South Asian Monsoon
Authors: Strnad Felix , Goswami Bedartha
Published: March 2022

Climate networks have recently helped to unravel spatial patterns of extreme rainfall events (EREs). However, EREs remain challenging to analyse due to their inherent stochasticty involved in their local distribution and intensity. Here, we present a principled approach to identify regions of similar ERE dynamics with the idea that this will help developing ERE prediction schemes in a later study.
We use a probabilistic approach to quantify community structures and estimating the structural uncertainties involved in the community detection process. First, we use time-delayed event synchronization to construct a network of ERE teleconnections. Using a Bayesian hierarchical community detection algorithm based on the Stochastic Block Model (SBM) enables us to estimate the likelihood that spatial locations belong to the same community via a point-wise spatial density analysis.
We apply our method to the South Asian Monsoon system and reveal a latitudinal band-like structure of synchronous EREs, whose occurrence is consistent with the onset and withdrawal of the monsoon season. Moreover, we demonstrate that exceptionally strong synchronization is observed when a fast developing low pressure system over the South China Sea occurs, as demonstrated by climatologies of days with maximum synchronization. 
An analogue based forecasting system for Mediterranean marine litter concentration
Authors: Jordà Gabriel , Soto-Navarro Javier
Published: March 2022

The pollution of the seas and oceans due to plastic waste has become one of the environmental problems that generate the most concern, both for the scientific community and for society as a whole. In that framework, marine litter (ML) forecasting systems are potentially a powerful tool for an efficient management of ML, to optimize the removal strategies  and/or to better characterize the ML distribution. ML forecasting systems are typically based on explicit numerical models which simulate ocean currents and, afterwards, the advection and diffusion of passive particles in the ocean that mimic the evolution of ML. This approach is considered to be the most accurate one, at least as accurate as the quality of the forcing and the initial conditions are. However the downside is that this approach involves a high technical complexity and computational cost. In order to overcome those limitations we propose to explore a new approach implementing a fast and light forecasting system based on the analogue downscaling method. The main idea is to use statistical properties of the ML concentration fields, and the relationship between those fields and the state of the atmosphere to produce ML forecasts from atmospheric forecasts, which are readily available by several meteorological services. As this is a new approach never tested before for ML concentration forecasts, the first step will be to run several tests to fine-tune the methodology and to characterize its limits of validity.

Our results show that the analog-based forecast method presented here has potential to become a suitable cost effective forecasting method for ML concentration. The quality of the forecasts depends on the region of application: the larger the region of application the better, as we get better results for the whole Mediterranean or for the East/West basins than in smaller local areas. The method struggles to capture the extreme values as it produces smooth spatio-temporal patterns of ML concentration. Therefore, in locations or regions where short intense events or small scale features dominate the variability, the method performs worse. On the other hand, if instead of the time variability, what are aimed at are the spatial structures, the method shows high skills.
Imaging the uppermost layers of the Eifel volcanic system (Germany) using ambient microseismic noise
Authors: Barrière Julien , Oth Adrien
Published: March 2022

The Eifel region is a large volcanic system in the middle of European continent. From the Eifel teleseismic tomography experiment (8 months in 1997-1998), a mantle plume beneath the volcanic fields (down to 400 km depth) has been identified and further confirmed by receiver function and teleseismic surface wave dispersion analyses. A study in 2020 using dense geodetic observations leads to the conclusion that the Eifel region experiences a pronounced uplift encompassing the neighbouring countries Netherlands, Belgium, Luxembourg and France, which is attributed to the same buoyant mantle plume.

A detailed focus on the uppermost 30 km above the Moho has been missing until recently. However, a noteworthy recent seismological investigation showed the evidence of a deep magmatic recharge beneath the Laacher See Volcano in East Eifel between 2013 and 2018. Located at depth roughly between 40 and 10 km, low-frequency seismic swarms, which are typical of volcanic environment, convey the presence of magma movements and potential storage zones in the crust.  

The present study aims to bring additional information on this shallow active magmatic system using an Ambient Noise Tomography (ANT). Thanks to theoretical and technical developments over the two last decades, this approach has been increasingly popular for imaging Earth structure worldwide at different scales. We use here ambient noise data from archives of the 1997-1998 Eifel experiment and more recent (2019-2020) continuous seismic record. The group velocity dispersion of Rayleigh waves are estimated between station pairs from Noise Cross-correlation Functions (NCF) covering the secondary microseismic frequency band, which allows to sample the uppermost 10-20 km of the crust. Our contribution includes a complete description of the ANT/NCF processing (e.g., directivity of the noise sources, sensitivity tests) in order to better constrain the velocity anomalies observed in the Eifel region and around.
Thermo-rock: influence of temperature on rock slope properties
Authors: Racek Ondřej , Blahůt Jan
Published: March 2022

Thermo-rock: influence of temperature on rock slope properties

Rock slope stability is closely linked with the mechanical properties of the rock slope mass. These properties are influenced by numerous factors including meteorological, thermal and hydrogeological. Even short-term temperature cycles caused by direct sunlight, together with water saturation cycles can change mechanical properties of rock slope surficial zone. To partially quantify these influences, we have carried out short-term experiments at a former quarry test site. Geotechnical instrumentation of partial blocks with crack meters, surface and microcracks deformation monitoring using strain gauges, geophysical ERT monitoring, subsurface temperature and humidity monitoring, and  IR camera surface temperature sensing were used during 24-hour monitoring campaigns. Additionally, surface hardness was repeatedly measured using Schmidthammer. Before and after monitoring campaigns, rock mass samples from different depths were collected, to perform basic geomechanical tests. Using these complex data, the influence of short-term temperature changes on the rock slope surficial layer properties were estimated.
Characterization and permanent monitoring of the hydraulically active zones of a deep geothermal reservoir using a fiber-optic monitoring system in a production well in the Bavarian Molasse Basin
Authors: Schölderle Felix , Pfrang Daniela , Meinecke Michael , Dirner Sebastian , Zosseder Kai
Published: March 2022

Interpretation and monitoring of hydraulically active zones in hydro-geothermal wells is critical for assessing the hydraulics of a reservoir and for understanding sustainable reservoir management. For this purpose, flowmeter runs are often performed during injection at the end of short-term pumping tests after the well is completed. Because conventional well designs do not allow direct monitoring in the reservoir once the well is in operation, it is often not clear whether the flowmeter's interpreted injection zones reflect subsequent production zones.

To gain insight into the long-term hydraulic and thermal behavior of geothermal wells in operation, a fiber-optic monitoring system was installed down to 3683 m MD of a geothermal production well in 2019 and below the electric submersible pump into the reservoir in 2021. The well is part of the Schäftlarnstraße geothermal site in Munich, Southern Germany, where six doublets develop the deep hydrothermal Upper Jurassic “Malm” reservoir of the Northern Alpine Foreland Basin. The fiber-optic monitoring system is the first of its kind installed permanently in a geothermal production well. It allows monitoring of temperature (distributed temperature sensing, DTS) and acoustic/strain (distributed acoustic sensing, DAS) continuously in space and time and of pressure and temperature at a fiber-optic gauge located at top of the reservoir at 2748 m MD.

Using DTS technology, the temperature inside the borehole was monitored when the wells at the geothermal site started production. The recorded data were used to analyze the temperature signature at the hydraulically active zones known from previous hydraulically injection tests (flowmeter and temperature monitoring during cold-water injection).

The results show that both hydraulics and production temperature are dominated by an active, karstified zone in the uppermost part of the reservoir of the monitored well. The production of another well of the three doublets geothermal site also strongly affects the temperature distribution in the monitored well. We highlight the importance of continuous monitoring and show the benefit of the permanent fiber-optic monitoring system for sustainable reservoir management.
The Kalmag and ArchKalmag14K geomagnetic field models: their derivation principle, properties and availability
Authors: Baerenzung Julien , Schanner Maximilian Arthus , Korte Monika , Saynisch Jan , Holschneider Matthias
Published: March 2022

The recent Kalmag and archaeomagnetic ArchKalmag14K models together represent the global geomagnetic field model evolution over the past 14000 years and resolve temporal scales of the order of a month over the last 122 years. They are obtained through the sequential assimilation of archeomagnetic and volcanic data, and survey, observatory and satellite data, respectively. Both these models provide full posterior information about the core field, and in the case of Kalmag also about other magnetic sources such as the lithospheric or some tidal fields. These models are made accessible online through different physical and statistical quantities associated with them. In this presentation, we will detail our modeling strategy, the type of results we are getting with it, and how the community can access and use our models by an online interface at https://ionocovar.agnld.uni-potsdam.de/Kalmag/ and https://ionocovar.agnld.uni-potsdam.de/Kalmag/Archeo/.
Observations and unstructured-grid simulations of tidally-generated eddies in a complex coastal environment
Authors: Espenes Håvard , Nøst Ole Anders , Isachsen Pål Erik
Published: March 2022

The Norwegian coastline is made up of a multitude of long and narrow fjords and straits. The near-shore flow here is severely restricted by the complex geometry, with subsequent consequences for the net transport and dispersion of biogeochemical material through the coastal zone.

One possibly important transport mechanism in such complex environments is non-linear pumping by vortex dipoles, generated by tidal currents through fjord and strait openings. Previous laboratory studies have demonstrated the transport capacity of such structures. And recent modelling studies have shown that the laboratory results should be relevant for coastal scale applications, also along the Norwegian coast. But there are still few observational studies of their existence and transport efficiency.

Recent mooring observations from Tromsø, Northern Norway, shows intermittent velocity maxima downstream of a tidally-dominated constriction. We reproduced similar signals using a high-resolution setup of the unstructured-grid ocean model FVCOM. The model shows that the velocity extrema occur when dipole vortices shed away from the constriction and propagate downstream to the mooring locations. We hypothesize that such dipoles develop when the constriction geometry allows for flow separation on both sides of the constriction, and that the dipoles leave the constriction when the dipole-generated sea surface depression is strong enough to break the adverse pressure gradient conditions required to achieve flow separation. The frequency of dipole formation - and velocity extrema - then depends on the forcing strength and constriction geometry.
Exploring spatiotemporal dynamics of soil moisture: three model conceptualizations in a subarctic catchment
Authors: Nousu Jari-Pekka , Leppä Kersti , Marttila Hannu , Ala-aho Pertti , Aurela Mika , Lohila Annalea , Launiainen Samuli
Published: March 2022

Surface soil parameters, especially soil moisture has a key role in soil nutrient cycling, greenhouse gas emissions, vegetation water use as well as energy and water exchanges between land and the atmosphere. In this study, we model soil moisture with three different model conceptualizations developed in Spatial Forest Hydrology model (SpaFHy) in a subarctic Pallas catchment in Northern Finland, covered by coniferous forests and peatlands. The model versions differ in how the groundwater flow is treated, which is shown to have a clear impact on the spatiotemporal soil moisture dynamics within the catchment. The conceptualizations range from i) neglecting groundwater storage, to ii) TOPMODEL approach, and to iii) spatially distributed groundwater flow model. By comparing these scenarios, we are able to assess when and where solving the 2D ground water flow is prerequisite for accurate predictions of soil moisture, and in which conditions soil moisture variability is driven more by local processes. The model results are compared against continuous point-scale measurements, and spatially against distributed measurement campaigns conducted in the study area. In addition, we compare the spatiotemporal soil moisture simulations with novel SAR-based soil moisture maps. SAR signal is well suited to estimate topsoil moisture thanks to its high sensitivity to water. However, different topographic and vegetation settings create challenges for SAR signals to capture the properties of soil, and thus, SAR soil moisture estimates have not been as widely used in forested areas. Remote sensing products such as SAR-based soil moisture maps possess a major potential to further develop spatially distributed land surface and hydrological models.
Wave-like structures prior to very recent southeastern Mediterranean earthquakes as recorded by a VLF/LF radio receiver in Athens (Greece)
Authors: Politis Dimitrios Z. , Potirakis Stelios M. , Biswas Sagardweep , Sasmal Sudipta , Hayakawa Masashi
Published: March 2022

A VLF (10 – 47.5 kHz) radio receiver with call sign UWA has recently been installed at the University of West Attica in Athens (Greece) and is continuously monitoring the lower ionosphere by means of the receptions from many transmitters, in order to identify any possible pre-seismic signatures or other precursors associated with extreme geophysical and space phenomena. In this study, we examine the case of three very recent strong mainshocks with magnitude Mw ≥ 5.5 that happened in September and October of 2021 in the southeastern Mediterranean. The VLF data used in this work correspond to the recordings of one specific transmitter with the call sign “ISR” which is located in Negev (Israel). The borders of the 5th Fresnel zone of the corresponding sub-ionospheric propagation path (ISR-UWA) are close in distance with the epicenters of the two earthquakes (EQ), while the third one is located within the 5th Fresnel zone of the specific path. In this work, we computed the morlet wavelet scalogram of the nighttime amplitude signal in order to check for any embedded wave-like structures, which would indicate the existence of Atmospheric Gravity Waves (AGW) before each one of the examined EQs. In our investigation, we also checked for any other global extreme phenomena, such as geomagnetic storms and solar flares, which may have occurred close in time with the examined EQs and could have a contaminating impact on the obtained results. Our results revealed wave-like structures in the amplitude of the signal a few days before the occurrence of these three EQs.
Assessing co-benefits of urban greening coupled with rainwater harvesting management under current and future climates across USA cities
Authors: Zhang Ziyan , Paschalis Athanasios , Mijic Ana , Dobson Barnaby , Butler Adrian
Published: March 2022

Globally, urban areas will face multiple water-related challenges in the near future. The main challenges are intensified droughts leading to water scarcity, increased flood risk due to extreme rainfall intensification, increased total water demand due to an increasing urban population, amplified urban heat island intensities due to urban sprawl, and reduction in urban carbon sink due to plant water stress. Urban greening is an excellent option for mitigating flood risk and excess urban heat. Meanwhile, rainwater harvesting (RWH) systems can cope with water supply needs and urban water management. In this study, we investigated how urban greening and RWH can work together to mitigate the aforementioned risks. We evaluate the joined-up management approach under climate projections for 30 cities in the USA spanning a variety of climates, population densities and urban landscapes. By incorporating a new RWH module in the urban ecohydrological model UT&C and flexible operational rules of reusing harvested water for domestic use and urban green space irrigation, we tested 4 intervention approaches: control, RWH installation, urban greening supported by RWH, and urban greening supported by traditional irrigation (i.e., supplying via mains water). Each intervention approach was evaluated using our adapted version of UT&C and forced by the last generation convection-permitting model simulations of current (2001-2011) and end-of-century (RCP8.5) climate from Weather Research and Forecasting (WRF). The volume of RWH is assumed to be 2000L per household for all cities. Results showed that neither urban greening nor RWH could contribute significantly to reducing the expected increase in canyon temperature, because of the strong change in background climate (i.e., increases in average atmospheric temperature). However, RWH alone can sufficiently reduce the intensifying surface flood risk and effectively enhance water conservation, and urban greening can significantly increase the carbon sink of cities especially in dry regions, and if supported by traditional irrigation. Those results vary with the background climate: the benefits of urban greening, either supported by RWH or traditional irrigation, on canyon temperature reduction and carbon sink improvement increased with average air temperature and decreased with wetness index respectively; the benefits of RWH on runoff reduction and water conservation are both positively dependent on local annual precipitation.
Spatio-temporal Graph Neural Networks for Ionospheric TEC Prediction Using Global Navigation Satellite System Observables
Authors: Kaselimi Maria , Gikas Vassilis , Doulamis Nikolaos , Doulamis Anastasios , Delikaraoglou Demitris
Published: March 2022

Precise modeling of the ionospheric Total Electron Content (TEC) is critical for reliable and accurate GNSS applications. TEC is the integral of the location-dependent electron density along the signal path and is a crucial parameter that is often used to describe ionospheric variability, as it is strongly affected by solar activity. TEC is highly depended on local time (temporal variability), latitude, longitude (spatial variability), solar and geomagnetic conditions. The propagation of the signals from GNSS (Global Navigation Satellite System) satellites throughout the ionosphere is strongly influenced by temporal changes and ionospheric regular or irregular variations. Here, we propose a deep learning architecture for the prediction of the vertical total electron content (VTEC) of the ionosphere based on GNSS data. 

The data used in many deep learning tasks until recently where mostly represented in the Euclidean space. However, geodesy studies data that have an underlying structure that is non-Euclidean space. Geospatial data are large and complex, as in the case of GNSS networks data, and their non- Euclidean nature has imposed significant challenges on the existing machine learning algorithms. The task of VTEC prediction is challenging mainly due to the complex spatiotemporal dependencies and an inherent difficulty in temporal forecasting. Spatial-temporal graph neural networks (STGNNs) aim to learn hidden patterns from spatial-temporal graphs. The key idea of STGNNs is to consider spatial and temporal dependency at the same time. Spatial Dependency: Assuming a network of permanent stations of International GNSS Service (IGS), each station represents a node of the graph, and their Euclidean distance is used to formulate the set of edges of the graph. Thus, we achieve exchange between nodes and their neighbors. Temporal dependency: The graph operates in a dynamic environment. Thus, we leverage the recurrent neural networks (RNNs) to model the temporal dependency. As a result, time series of VTEC data can be predicted to future epochs. Solar and geomagnetic indices are formulated as node attributes and are also present temporal variability.

Topics to be discussed in the study include the design of the graph neural network structure, the training methods exploiting steepest descent algorithms, data analysis, as well as preliminary testing results of the VTEC predictions as compared, with state-of-the-art graph architectures.
Sub-mesoscale evolution of spatial wind gust patterns measured with three Doppler lidars in a triangle configuration
Authors: Steinheuer Julian , Beyrich Frank , Detring Carola , Fiedler Stephanie , Friederichs Petra , Löhnert Ulrich
Published: March 2022

The evolution of wind gusts is difficult to observe as gusts are short-lived and small-scale phenomena. They occur with certain weather configurations (e.g. fronts, cold pools) and may already differ very locally. The question arises if individual gust observations can be taken as representative of their surroundings or if significant differences can already be apparent on the meso-gamma scale (2-20 km). Within the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) different phenomena in the atmospheric boundary layer are studied with a variety of measurement instruments. This involved installing three StreamLine DWL systems from Halo Photonics at a distance of 6 km apart from each other. DWLs allow the retrieval of wind vector profiles and offer an alternative to classic meteorological tower observations, since they can be flexibly deployed at any electrified site. However, short-lived gusts are more difficult to capture than a persistent mean wind. A wind vector has to be obtained from different radial velocity measurements that are made sequentially, which limits the achievable temporal resolution. Therefore, we have developed a new retrieval method for deriving wind measurements that is suitable for different scan configurations and different time resolutions respectively different numbers of radial velocities. A fast continuous scanning mode (CSM), that completes a full observation cycle within 3.4 seconds and measures about eleven radial Doppler velocities is a suitable DWL configuration for deriving wind gusts, as shown by comparisons with measurements of a sonic anemometer at 90.3 m a.g.l. on the meteorological tower in Falkenberg. The fast CSM configuration was operated on the DWLs during the summer months 2021 at the three different sites. Their surrounding area is predominantly flat farmland, minimizing topographic impacts. This set-up allows us to observe the spatial-temporal evolution of gusts at the meso-gamma scale. Examples will be presented that illustrate the variability of wind gusts as observed during FESSTVaL.
Estimation of Non-Linear Water Uptake Parameter using Genetic Algorithm for Sodic Soils
Authors: Goet Gaurav , Sonkar Ickkshaanshu , Hari Prasad Kotnoor
Published: March 2022

In the plant water soil system, water plays a vital part in controlling the plant's growth. The plant fulfils its water demand from the soil water through root uptake. The pattern of water uptake by the plant through roots depends on the root geometry and the root density, which varies non-linearly with the depth. To quantify this non-linearity, it is essential to precisely determine the parameter accounting for this non-linearity in the water uptake. Moreover, it has also been observed in the literature that sodicity alters the root growth and thence the density. The current study is about identifying non-linear root water uptake parameter utilizing the Genetic Algorithm (GA) technique in Sodic soils. Different models have been proposed to predict root water uptake by the plants. The non-Linear nature of root water uptake has been confirmed from previous studies and observations. The non-linear root water uptake model named as O-R (Ojha and Rai, 1996) model combined with soil moisture flow or Richard's equation is developed to determine the pattern of root water uptake by the plants. Non-linear parameter β is incorporated in the O-R model to account for non-linearity in the uptake. In the current study, parameter β is determined through inverse modelling utilizing GA optimization procedure. For parameter optimization, the difference between model-predicted and experimentally observed percentage soil moisture depletion is minimized for soils of different salinity classes. To check the viability of the developed model, the optimization procedure is validated from hypothetically generated percentage soil moisture depletion corresponding to an assumed β value and salt concentration in the soil. This study considers the wheat crop (Triticum) to apply this model and estimate the non-linear root water uptake parameter β. The results obtained show that the linked simulation-optimization model based on GA procedure precisely determines the non-linear root water uptake parameter for the Wheat crop considered. Since Different crops follow different non-linear water uptake patterns and hence, have different values of β. Thus, an accurate estimation of β is necessary to analyze the root water uptake and plan the irrigation scheduling strategies for modern agriculture.