bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards an IAG combined global GNSS velocity field
Authors: Santamaría Alvaro , Rietbroek Roelof , Frederikse Thomas , Rebischung Paul , Legrand Juliette
Published: March 2022

GNSS velocities estimated by different analysts can significantly differ due to the choices made concerning the GNSS data processing (corrections applied and noise level of the series), the completeness of the series, the removed position discontinuities and the alignment to a terrestrial reference frame. The position discontinuities that populate the GNSS time series have probably the biggest impact on the error or dispersion of the velocity estimates at the same sites. Even when using exactly the same position series, different analysts may provide different velocity estimates and uncertainties mainly due to the choice of removing different position discontinuities.

The IAG Joint Working Group 3.2 (2019 – 2023) aims at providing a global combined GNSS velocity field that takes into account the repeatability, the alignment and the relative weighting of the velocity estimates by different groups. We expect that this IAG’s unified GNSS velocity field will be useful for the scientific community inside, but especially outside, the geodetic community in areas such as tectonics, sea-level change and GIA modeling among others.

In this contribution, we present the current status of the global combined velocity field, aligned to the recently released ITRF2020, and based on the velocity fields provided by several other groups.
A new K-ε  turbulence parameterization  for mesoscale meteorological models
Authors: Zonato Andrea , Martilli Alberto , Jimenez Pedro A. , Dudhia Jimy , Zardi Dino , Giovannini Lorenzo
Published: March 2022

A new one-dimensional 1.5-order planetary boundary layer (PBL) scheme, based on the K-ε turbulence closure applied to the Reynolds-averaged-Navier-Stokes (RANS) equations, is developed and implemented within the Weather Research and Forecasting (WRF) model. The new scheme includes an analytic solution of the coupled equations of the turbulent kinetic energy and of the dissipation rate. Different versions of the PBL scheme are proposed, with increasing levels of complexity, including a model for the calculation of the Prandtl number, a correction to the dissipation rate equation, and a prognostic equation for the temperature variance. Five different idealized cases are investigated: four of them explore convective conditions, and they differ in initial thermal stratification and terrain complexity, while one simulates the very stable boundary layer case known as GABLS. For each case study, an ensemble of different Large Eddy Simulations (LES), has been taken as reference for the comparison with the novel PBL schemes and other state-of-the-art 1- and 1.5-order turbulence closures. Results show that the new PBL K-ε  scheme brings improvements in all the cases tested in this study. Specifically, the largest enhancements are brought by the turbulence closure including a prognostic equation for the temperature variance. Moreover, the largest benefits are obtained for the idealized cases simulating a typical thermal circulation within a two-dimensional valley. This suggests that the use of prognostic equations for the dissipation rate and temperature variance, which take into account their transport and history, is particularly important with increasing complexity of PBL dynamics.
Equatorial waves on the β-plane in the presence of a uniform zonal flow: Beyond the Doppler shift
Authors: De-Leon Yair , Paldor Nathan , Garfinkel Chaim I.
Published: March 2022

Numerical solutions of the eigenvalue equation associated with zonally propagating waves of the Linearized Rotating Shallow Water Equations are derived in a channel on the equatorial β-plane in the presence of a uniform mean zonal flow. The meridionally varying mean height field is in geostrophic balance with the prescribed mean zonal flow. In addition to the trivial Doppler shift of the free waves’ phase speeds, the mean state causes the dispersion curves of each of the free Rossby and Poincaré waves to coalesce in pairs of modes when the zonal wavenumber increases. For large zonal wavenumber or large mean flow, the latitudinal variation of the waves’ amplitudes differs from that of free waves i.e., Hermite Functions (in wide channels) and Harmonic Functions (in narrow channels) do not describe the amplitude structure. For large mean speed and for large zonal wavenumber the eigenvalue problem loses its Sturm-Liouville structure and the eigenfunctions have multiple extrema between successive zeros of the function itself. In contrast to free Kelvin waves, in the presence of a mean flow the meridional velocity component of these waves does not vanish identically. For zonal stratospheric winds of order 20 m s-1 and for gravity wave speed of order 25 m s-1 the phase speed with mean wind can be twice that of the classical theory with no mean zonal wind.
The atmospheric response to the Weddell Sea Polynya
Authors: Ayres Holly , Ferreira David
Published: March 2022

The Weddell Sea Polynya is a large opening within the sea ice cover of the Weddell sea sector, typically found sitting over the Maud Rise in its largest occurrences. It has been a rare event in the satellite period, appearing throughout the 1970s and again in 2016/17. Many mechanisms have been suggested to cause the onset of the Weddell Sea Polynya, from deep convection of the ocean and upwelling at the Maud Rise, in addition to increased cyclone activity and the influence of atmospheric rivers. It is thought that with increasing atmospheric greenhouse gasses, the Weddell Sea Polynya will be even less frequent, due to an intensification of the haline stratification within the polynya region. The opening of the polynya creates an ocean to air heat flux in the cooler months, with the potential to influence atmospheric dynamics. The atmospheric response to the polynya and regional ice loss may be observed locally within the low-pressure region of the Weddell Sea or further afield climate. Here, we use high and low resolution AGCM experiments with the HadGEM3 UK Met Office model, alongside PRIMAVERA high-resolution analysis of the polynya, to evaluate the atmospheric response to the polynya and associated features, in addition to the role of model resolution in resolving the polynya and its associated features.
Experimental constraints on low temperature dehydration induced by mineral reactions in calcite-bearing ophicarbonates
Authors: Eberhard Lisa , Plümper Oliver , Frost Daniel J.
Published: March 2022

It is generally accepted that subduction zones are important sites for element recycling into the Earth’s mantle. This does in particular also include carbon, which is transported in the form of organic carbon and carbonates. While organic carbon is expected to effectively fix carbon in the slab, carbonates are often entitled as an important CO2 source for arc magmatism. The exact composition of the total subducted carbon load, in terms of oxidised and reduced carbon material, changes between different slabs and consequently the total released carbon varies significantly among suduction zones. An important mechanism for carbon release is the dissolution of carbonates in aqueous fluids. Ophicarbonates, containing both serpentine and carbonate minerals, are thus of special interest: The fluid released through serpentine dehydration reactions interacts with carbonates and causes the release of carbon. However, to better constrain the carbon release it is essential to understand the release of fluid in carbonated systems.

In this study we present a detailed experimental analysis on the effect of carbonates on the fluid release from serpentinites. We performed multi-anvil experiments on model ophicarbonates. Our starting material was a mixture between natural antigorite and Ca-carbonate and/or graphite. We also conducted thermodynamic calculations on various serpentinite-carbonate systems. Our experimental results show that serpentine dehydrates at temperatures <600 °C at 2.5 GPa, which is lower with respect to uncarbonated serpentinites. For a serpentinite with 20 wt% CaCO3 the dehydration of serpentine thus takes place at 50 - 60 km depth. In the absence of CaCO3 the fluid is released at 60 - 70 km depth. In cold subduction zones this shift in dehydration depth is even more extreme: In a carbonated system the serpentine was found to dehydrate at 80 - 110 km depth, in comparison to 110 - 130 km depth in the uncarbonated system. We found that this shift is mainly due to Ca-Mg exchange reactions between the carbonate and silicate fraction. The experimental run products show distinct dehydration mineralogy, forming Ca-silicates and Mg-bearing carbonates. In combination with mass balance calculations we show that the total carbonate-fraction does not decrease over the whole experimental temperature range. In conclusion, serpentinites with a high Ca-carbonate content are expected to dehydrate earlier in the subduction zones, whereas the carbon remains in the slab. The presence of Ca-carbonate thus has the potential to prevent subduction of water into deeper levels of the Earth’s mantle.
Diurnal anisotropy of polar neutron monitors, Dome C looks poleward
Authors: Gil Agnieszka , Mishev Alexander , Poluianov Stepan , Usoskin Ilya
Published: March 2022

Galactic cosmic rays (GCR) show a small local anisotropy detected as a diurnal variability of neutron monitor (NM) count rates. As the asymptotic directions of different NMs are diverse, the capability of the GCR diurnal variation observation is also various. Here we present that the Dome C (DOMC) NM is barely sensitive to the diurnal variation. Its amplitude is very small, 0.03%, in comparison to other polar NMs, for which the diurnal variability amplitudes vary from 0.16 to 0.4%. This fact is associated to the narrow asymptotic-direction cone of DOMC NM looking almost to the South pole with geographic latitude above 75o. Thus, DOMC NM is the only existing NM accepting cosmic-ray particles from the off-equatorial region, which makes this station a unique detector.
Compound flooding due to interaction of waves and river discharge at Breede Estuary, South Africa
Authors: Kupfer Sunna , Santamaria-Aguilar Sara , van Niekerk Lara , Lück-Vogel Melanie , Vafeidis Athanasios T.
Published: March 2022

Recent studies on compound flooding have considered the interaction of storm surge and fluvial or pluvial flood drivers, whereas the contribution of waves to compound flooding has so far been neglected. In this study, we assess compound flooding from waves, tides and river discharge at Breede Estuary, South Africa, using a hydrodynamic model. We estimate the contribution of extreme waves to compound flooding by analysing the driver interactions and by quantifying changes in flood characteristics. We further consider the effect of waves on flood timing and compare results of compound flood scenarios to scenarios in which single drivers are omitted. We find that flood characteristics are more sensitive to river discharge than to waves, particularly when the latter only coincide with high spring tides. When interacting with river discharge, however, the contribution of waves is high, causing larger flood extents and higher water depths. With more extreme waves, flooding can begin up to 12 hours earlier. Our findings provide insights on the magnitude and timing of compound flooding in an open South African estuary and demonstrate the need to account for the effects of waves during compound flooding in future flood impact assessments of similar coastal settings with similar wave climates.
Mode-2 internal waves and inter-mode resonance in late winter lakes
Authors: Stastna Marek
Published: March 2022

In late winter/early spring temperate and northern lakes often experience a so-called weak, inverse stratification.  This occurs since: i) fresh water experiences a maximum density at around four degrees Centigrade, ii) the lake is iced over and thus mechanically isolated from the overlying atmosphere, iii) the increasing solar insolation heats the water column according to the Beer-Lambert-Bouguer law; thereby producing a region of instability that mixes a portion of the water column.  This classical scenario fits some lakes, but the small density differences due to the thermal forcing also imply that very small amounts of dissolved salts could create a more complex, combined solute-thermal stratification.  We explore the behaviour of nonlinear internal waves for one such measured stratification. For mode-1 we find well defined internal solitary waves. For mode-2 the coupling between pycnoclines is weaker leading to a more complex dynamics that we quantify in detail. 
Preliminary airborne geophysical surveys over the Bou Azzer-El Graara inlier (Central Anti-Atlas, Morocco): implications for geodynamic model of the Anti-Atlas Pan-African belt
Authors: Ilmen Saïd , Anzar Fouzia , Soulaimani Abderrahmane , Jaffal Mohamed , Bajddi Amine , Maacha Lhou , Baidada Bouchra
Published: March 2022

The Anti-Atlas orogenic belt, located at the northwestern edge of West African Craton, hosts several Proterozoic antiformal inliers (Boutonnières) which crops out under a thick Paleozoic Cover. In its central part, along the Anti-Atlas Major Fault, the Siroua and Bou Azzer-El Graara inliers exhibit Neoproterozoic ophiolitic suture which subduction settings is still under debate. In the last two decades, huge scientific publications were done in this area, mainly focused on the structural, petrological and geochronological issues. Three broad tectonothermal events were recognized in the Pan-African cycle. The Tonian–Cryogenian period ends with the obduction of supra-subduction ophiolite and oceanic arc material at ca. 640 Ma. The Early Ediacaran period was marked by the development and subsequent closure of a wide marginal basin next to a likely Andean-type arc (Saghro Group). The Late Ediacaran period is recorded by subaerial molasse deposits associated with post-collisional high-K calc-alkaline to shoshonitic magmatism (Ouarzazate Group).This project aims to use the magnetic and electromagnetic data of the Bou Azzer-El Graara inlier, and to integrate their interpretations in the geodynamic model of the Anti-Atlas Pan-African belt. The preliminary interpretations of the available aeromagnetic data show high-level magnetic signature at the western part of the Bou Azzer inlier, while it is missing in the east of the CAMP Foum Zguid dyke. From the Bou Ofroukh at the western tip of the inlier to the Ait Abdellah village, the strength of the magnetic signal is related to the wide exposure of the ultramafic rocks along the Anti-Atlas Major Fault. A weakness of the magnetic signal is observed in the area situated between Bou Azzer and Aghbar mines. This weakness was interpreted as being due to the deeply buried serpentinites under the Ediacaran volcano-sedimentary sequence. However, filed maps and magnetic signature indicate the absence of magnetic signal and the ultramafic rocks at the eastern domain of the Bou Azzer-El Graara inlier from the Foum Zguid dyke eastward. Several pending questions should be emphasized on the structural framework and continuity of the Anti-Atlas Major Fault and the role played by this inherited NE-SW Fracture infilled by Lower Liassic dolerite during the Pangea breakup.
Fifty years long soil development due to seasonal water-saturation under hydric conditions
Authors: Szalai Zoltán , Ringer Marianna , Sipos Péter , Németh Tibor , Pekker Péter , Jakab Gergely
Published: March 2022

Pedogenesis is considered a long-term environmental process; however, it can be accelerated by periodic water saturation (hydric conditions). The exact nature and effectiveness of hydric conditions in the intensification of soil development are not clear yet. Our understanding of the timescales of the mineralogical changes occurring in soils is limited; however, the timeframe of soil organic matter accumulation is broadly known. Here, we described soil development over a period of 50 years.

The studied soils Calcaric Mollic Gleysol (Endoarenic, Epiloamic, Hyperhumic) and a Calcaric Calcic Histic Gleysol (Endoarenic, Epiloamic) are located in a swampy meadow in Hungary, Central Europe. The start of the soil formation process is well documented here; the parent material was deposited during a major flood event in 1963. Therefore, the examined soil profile represents development over the last 50 years. We also studied the parent material of an adjacent dune as a reference. We used a CN elemental analyser to determine soil organic carbon and total bound nitrogen content. Selective extractions were also used to determine amorphous and crystalline Fe and Mn content alongside X-ray phase analysis (XRD) and transmission electron microscopy (TEM) for mineralogical analysis, X-ray fluorescence spectroscopy (XRF) for elemental analysis, and laser diffraction for particle size analysis of the bulk soil samples. Simple chemical tests were also performed in the field. Redox potential (Eh) and pH were measured by a field monitoring station.

Fifty years under hydric conditions resulted in rapid vertical differentiation within the soil profile, including remarkable soil organic matter enrichment in the topsoil and the formation of smectite and Fe accumulation in the zone of groundwater fluctuation. A high proportion of amorphous and colloidal phases indicated that very intense processes had taken place in the most intensive redox oscillation zone. The presence of more crystalline goethite in the bulk soil reflects frequent Eh changes associated with chemical or microbial processes. In contrast, the presence of amorphous ferrihydrite indicates the effect of plant roots. Permanently reductive and alkaline subsoil conditions also facilitated intense carbonate precipitation.

The presentation is based on Szalai et al. 2021 GEODERMA https://doi.org/10.1016/j.geoderma.2021.115328 and Ringer et al. 2021. HUNGEOBULL https://doi.org/10.15201/hungeobull.70.4.6.

The research was supported by the Eotvos Lorand Research Network (SA41/2021) and the Hungarian Scientific Research Fund (K123953).
Quantifying land-surface albedo feedback using Dansgaard-Oeschger events
Authors: Liu Mengmeng , Prentice Iain Colin , Harrison Sandy P.
Published: March 2022

Land-surface shortwave albedo is an important quantity in the energy budget of the Earth. Remotely sensed snow cover, maximum tree height and maximum fractional absorbed photosynthetically active radiation (fAPAR) explain 87% of the variation in present-day annual mean land surface albedo (weighted by the seasonal cycle of shortwave radiation) in a generalized linear model. We can therefore apply this model during Dansgaard-Oeschger (D-O) warming events during the last glacial period. We have already used these repeated, rapid (50–200 year), near-global climate-change events to provide new quantifications of Earth system feedbacks involving atmospheric CO2, CH4 and N2O. We now reconstruct maximum tree height and maximum fAPAR based on a new global compilation of pollen data covering the relevant time interval, combined with snow cover changes during simulated D-O events, in order to reconstruct global changes in radiative forcing due to changes in vegetation and snow cover – and thereby quantify the global land-surface albedo feedback.
High return level estimates of daily ERA-5 precipitation in Europe estimated using regionalized extreme value distributions
Authors: Rivoire Pauline , Le Gall Philomène , Favre Anne-Catherine , Martius Olivia , Naveau Philippe
Published: March 2022

We provide return level estimates of seasonal daily precipitation for Europe derived from the ERA-5 reanalysis data. This information is needed for a number of hydrological planning purposes (protective infrastructure, dams, retention basins) but is also an area of interest when considering climate change and associated changes in extreme precipitation and associated impacts. The large data set size, over 20'000 land grid points, makes the inference of pointwise return levels onerous. One major goal of statistical climatology is to summarize complex spatio-temporal variations of climatic variables and their extremes using a small number of statistical parameters. Regional Frequency Analysis addresses this challenge by defining homogeneous regions consisting of points with similar distributions of extremes (up to a normalizing factor) and developing so-called regional models, i.e. models that require few parameters. We apply a recently developed method to cluster precipitation data in space and fit a regional model to continent-wide precipitation data with the following objectives: i) come up with a "cooking recipe" of how to efficiently upscale the method to handle a continental-size data set (including discussion of limitations and practical challenges and a github repository: https://github.com/PhilomeneLeGall/RFA_regional_EGPDk ), ii) illustrate the gain in reducing the number of parameters in the statistical model by the new method, iii) and produce seasonal return-level estimates for precipitation in Europe using both estimates based on the new pooled method for land areas. The homogeneous regions that we identify depend on the local orography. We compare them to homogeneous regions identified in previous works that focused on the national scale. An assessment of local and regional models indicates that a relatively parsimonious model with only a spatially varying scale parameter can compete very well against complex models.
The potential role of wind-blown dust emissions in PM pollution over non-arid areas: a modeling study over Central Europe
Authors: Liaskoni Marina , Bartik Lukas , Huszar Peter
Published: March 2022

 

Wind-blown dust, emitted from the surface of the earth to the atmosphere as a result of the disintegration of material due to wind drag, can have a significant impact on the atmospheric concentration of PM levels, not only over arid, deserted areas, where their emission occurs, but due to long-range transport over distant areas too. Considering the increasing potential of longer dry periods between days with precipitation in a warming climate, one can expect however, that such emissions could be occasionally considerable also over non-arid areas, like Europe.

 

Here we provide a model based estimate of the regional impact of PM emissions from wind erosion (wind-blown dust - WBD) on urban and rural PM levels for a central European domain using a well-established wind-blown dust module (called ‘‘WBDUST’’) for the 2007-2016 period. As driving meteorological data, we used WRF simulations. WBD emissions were implemented into the CAMx chemistry transport model and we performed simulations with and without these emissions. Our results showed that both urban and rural PM levels are significantly increased if wind-blown dust is considered. The effects of the mineral content of WBD on ion chemistry and consequent effects on aerosol components (secondary (in-)organic aerosol) are analyzed too.
Coverage of in situ climatological observations in the world's mountains
Authors: Thornton James , Pepin Nicolas , Shahgedanova Maria , Adler Carolina
Published: March 2022

Many mountainous environments and ecosystems around the world are responding rapidly to ongoing climate change. Long-term climatological time-series from such regions are crucial for developing improving understanding of the underlying mechanisms responsible for such changes, and generating more reliable future impact projections for environmental managers and other decision makers. Whilst it is already established that high elevation regions tend to be comparatively under-sampled, detailed spatial and other patterns in the coverage of mountain climatological data have not yet been comprehensively assessed on a global basis. To begin to address this deficiency, we analyse the coverage of records associated with the mountainous subset of the Global Historical Climatological Network-Daily (GHCNd) inventory with respect to space, time, and elevation. Three key climate-related variables – air temperature, precipitation, and snow depth – are considered across 292 named mountain ranges. To characterise data coverage relative to topographic, hydrological, and socio-economic factors, several additional datasets were introduced. Spatial mountain data coverage is highly uneven, and there are several mountain ranges whose elevational range is severely under-sampled by GHCNd stations. Crucially, the three "Water Tower Units" previously identified as having the greatest hydrological importance to society appear to have extremely low station densities. Mountain station density is weakly related to the human population or economic output of the corresponding downstream catchments. A script we developed enables detailed assessments of record temporal coverage and measurement quality information. This contribution should help international authorities and more regional stakeholders to identify areas, variables, and other aspects that should be prioritised for investment in infrastructure and capacity. Finally, the transparent and reproducible approach taken throughout will enable the work to be rapidly repeated for subsequent versions of GHCNd, and may furthermore enable similar analyses to be efficiently conducted on other spatial reporting boundaries and/or environmental monitoring station networks. 
Integrated time-lapse geophysical imaging and remote-sensing study of the antropoghenic triggering of the landslides
Authors: Marciniak Artur , Majdański Mariusz , Kowalczyk Sebastian , Górszczyk Andrzej , Gajek Wojciech , Oryński Szymon , Stan-Kłeczek Iwona
Published: March 2022

In recent years, rapid climatic changes and their impact is widely visible and recognizable around the world. One of the effects of global warming is reduced snow cover in high-mountain areas. Such a situation leads to the case, where retaining snow cover suitable for the skiing activities is crucial. As a solution, heavy artificial snow with high water content is used. To prolongate the skiing season additional snow is produced and stored as a thick cover on the hillsides.  Such a heavy load leads to a situation, where slow-developing landslides with a tendency for rapid movements can occur. Such a situation can be potentially dangerous not only for the infrastructure but also for the humans themselves. Such a situation was observed in a study site in Cisiec (Silesian Voivodeship, Southern Poland), we're slowly developing landslide strongly affected the infrastructure on a small skiing resort. For a fuller understanding of the problem, precise geophysical imaging is required to distinguish of main triggering factors, as well as the anthropogenic impact on the landslide itself. In the presented study, the authors propose an integrated geophysical approach utilizing imaging techniques such as seismic reflection imaging and tomography, seismological monitoring, Electrical resistivity tomography (ERT), Audio-Magnetotellurics (AMT), laser scanning and photogrammetry for the monitoring time evolution of anthropogenically developed landslide. The integration of the results allows for obtaining a more certain image of the subsurface and its time evolution necessary for the studied problem. By using the uncertainty driven approach, where data is correlated with preserved information about its uncertainty, multiple interpretation mistakes can be solved. As a result, the authors were able to estimate the seasonal evolution of the landslide in relationship to the anthropogenic load on the hillside.

This research was funded by the National Science Centre, Poland (NCN) Grant 2020/37/N/ST10/01486.
Resolving the Influence of Ice Stream Instability on Postglacial Relative Sea-Level Histories: the case of the St Lawrence River Channel Ice Stream
Authors: Peltier Richard , Li Tanghua , Stuhnne Gordan , Velay-Vitow Jesse , Vacchi Matteo , Englehart Simon , Horton Benjamin
Published: March 2022

A challenge to understanding Late Quaternary glaciation history is the mechanism(s) responsible for the asymmetry in an individual glaciation cycle between the slow pace of glaciation and the more rapid pace of deglaciation (e.g., Broecker and Van Donk, 1970). It is increasingly clear that a major contributor to the rate of global deglaciation is the instability of marine terminating ice streams. Recent analyses by Velay-Vitow et al. (2020) suggest that these instabilities were often triggered by ocean tides of anomalously high amplitude. Examples include the Hudson Strait Ice Stream responsible for Heinrich Event 1 (H1) and the Amundsen Gulf Ice Stream. Here, we analyse the instability of the Laurentian Channel and St Lawrence River Channel ice stream system. Our analysis begins with the recognition of highly significant misfits of up to 60 m at ~9,000 calendar years ago between deglacial relative sea-level histories inferred by Vacchi et al. (2018) at sites along the St Lawrence River Channel and those predicted by the ICE-6G_C (VM5a) and ICE-7G_NA (VM7) models of the Glacial Isostatic Adjustment process. We suggest that these disagreements between models and data may be due to the St Lawrence River Channel ice stream becoming unstable during the deglaciation of the Laurentide Ice Sheet (LIS) due to the hypothesized tidal mechanism for ice stream destabilization. We investigate a sequence of scenarios designed to provide a best estimate of the timing of this event. Since this ice stream penetrated deeply into the interior of the LIS and was connected to the Laurentian Channel ice stream, the instability of the latter was required in order for destabilization of the St Lawrence River channel ice stream to be possible. We explore the consistency of the implied sequence of events with the observational constraints.
Enhance pluvial flood risk assessment using spatio-temporal machine learning models
Authors: Critto Andrea , Zanetti Marco , Allegri Elena , Sperotto Anna , Torresan Silvia
Published: March 2022

Extreme weather events (e.g., heavy rainfall) are natural hazards that pose increasing threats to many sectors and across sub-regions worldwide (IPCC, 2014), exposing people and assets to damaging effects. In order to predict pluvial flood risks under different spatio-temporal conditions, three generalized Machine Learning models were developed and applied to the Metropolitan City of Venice: Logistic Regression, Neural Networks and Random Forest. The models considered 60 historical pluvial flood events, occurred in the timeframe 1995-2020. The historical events helped to identify and prioritize sub-areas that are more likely to be affected by pluvial flood risk due to heavy precipitation. In addition, while developing the model, 13 triggering factors have been selected and assessed: aspect, curvature, distance to river, distance to road, distance to sea, elevation, land use, NDVI, permeability, precipitation, slope, soil and texture. A forward features selection method was applied to understand which features better face spatio-temporal overfitting in pluvial flood prediction based on AUC score. Results of the analysis showed that the most accurate models were obtained with the Logistic Regression approach, which was used to provide pluvial flood risk maps for each of the 60 major historical events occurred in the case study area. The model showed high accuracy and most of the occured events in the Metropolitan City of Venice have been properly predicted, demostrating that Machine Learning could substantially improve and speed up disaster risk assessment and mapping helping in overcoming most common bottlenecks of physically-based simulations such as the computational complexity and the need of large datasets of high-resolution information.
Extreme magnetopause locations and their sources
Authors: Nemecek Zdenek , Safrankova Jana , Grygorov Kostiantyn , Pi Gilbert , Aghabozorgi Nafchi Maryam , Nemec Frantisek , Simunek Jiri
Published: March 2022

Comparison of observed magnetopause locations with model predictions can serve as a proof of our understanding of the interaction between solar wind and Earth magnetic field. Since the corresponding upstream conditions are usually derived from observation at L1, our knowledge on solar wind propagation and evolution on short scales are tested as well. We have collected about 40 000 of magnetopause crossings observed by THEMIS spacecraft in course of 2007–2019 years and compared the observed magnetopause position with prediction of several empirical magnetopause models using OMNI upstream parameters (mostly derived from ACE observations) and Wind magnetic field and plasma measurements propagated by our two-step propagation routine. The difference between observed and predicted magnetopause radial distance, Robs – Rmod was used for quantification of the model-observation agreement. We have found that the distribution of Robs – Rmod can be well fitted by the Gaussian distribution with FWHM ≈1.2 Re for all models and both upstream monitors. Nevertheless, the tails of the distributions are enhanced for all models and Robs – Rmod larger than 2 Re are rather frequent. A detailed analysis of such events leads to suggestions for improvement of investigated models or for a building of a new empirical model of the equatorial magnetopause.
Assimilating cloud-affected visible & infrared satellite observations in idealized simulations
Authors: Kugler Lukas , Pierotti Nicola , Serafin Stefano , Weissmann Martin
Published: March 2022

Although cloud-affected satellite observations provide a promising source of information for convective-scale NWP, they are still rarely used in operational assimilation systems. This reveals that we do not fully understand the challenges involved in their assimilation as e.g. observation operator non-linearity, the non-linear evolution of clouds and unresolved scales of the model forecast. To mitigate these issues, we test various approaches for the assimilation of cloud-affected satellite observations in idealized simulations, i.e. within an observing system simulations experiments (OSSE) framework. We apply superobbing and thinning to visible and infrared observations, assimilate cloud-cover instead of radiance observations and study their effect on nonlinearity, aiming to linearize the relationship between observation and state variables and thus improve the assimilation procedure. We assimilate deep-convective systems in a 2-km Weather Research and Forecasting (WRF) model using the Data Assimilation Research Testbed's (DART) Ensemble Adjustment Kalman Filter with its novel interface to the radiative transfer model RTTOV. The latter includes MFASIS, a recently developed computationally efficient observation operator for satellite reflectances in the visible range.
Saturn ring structure inferred from comparison of Cassini observations with laboratory simulations
Authors: Nouzak Libor , Pavlu Jiri , Vaverka Jakub , Safrankova Jana , Nemecek Zdenek , Pisa David , Shen Mitchell , Sternovsky Zoltan , Ye Shengyi
Published: March 2022

Cassini spacecraft investigated the Saturn environment more than 13 years. In course of this long period, the RPWS (Radio Plasma Wave Science) experiment not only mapped electric fields in the Saturn’s magnetosphere but also registered a large number of sharp spiky signals caused by hypervelocity dust impacts within Saturn rings. We have identified more than 140 000 such waveforms recorded by electric antennas with 10 or 80 kHz cadence in a close proximity of the ring mid-plane (up to 0.2 Rs). Among them, shapes and amplitudes of more than 100 000 non-saturated impacts were corrected on the Cassini WBR (Wide Band Receiver) transfer function.

Our laboratory experiment with the 1:20 reduced model of Cassini positioned in the test chamber of the dust accelerator allowed us to determine dependences of the signal shape and amplitude on the dust parameters (velocity and mass) and spacecraft potential. We apply these results on calculations of the mass and size distributions of dust particles detected by the electric field antennas within the Saturn ring system. The core of the paper is devoted to relation between dust characteristics (determined from impact signals and local plasma parameters) and ring mass profiles at distances ranging from 2 to 60 Rs from the surface.
Uncertainty in projected changes in precipitation minus evaporation: Dominant role of dynamic circulation changes and weak role for thermodynamic changes
Authors: Elbaum Eilat , Garfinkel Chaim I. , Adam Ori , Morin Efrat , Rostkier-Edelstein Dorita , Dayan Uri
Published: March 2022

End of century projections from Coupled Model Intercomparison Project (CMIP) models show a decrease in precipitation over subtropical oceans that often extends into surrounding land areas, but with substantial intermodel spread. Changes in precipitation are controlled by both thermodynamical and dynamical processes, though the importance of these processes for regional scales and for intermodel spread is not well understood. The contribution of dynamic and thermodynamic processes to the model spread in regional precipitation minus evaporation (P-E) is computed for 48 CMIP models. The intermodel spread is dominated essentially everywhere by the change of the dynamic term, including in most regions where thermodynamic changes dominate the multi-model mean response. The dominant role of dynamic changes is insensitive to zonal averaging which removes any influence of stationary wave changes, and is also evident in subtropical oceanic regions. Relatedly, intermodel spread in P-E is generally unrelated to climate sensitivity.
BEST-WR for the hydraulic characterization of hydrophilic and water-repellent soils
Authors: Di Prima Simone , Stewart Ryan D. , Abou Najm Majdi R. , Ribeiro Roder Ludmila , Giadrossich Filippo , Angulo-Jaramillo Rafael , Yilmaz Deniz , Roggero Pier Paolo , Pirastru Mario , Lassabatere Laurent
Published: March 2022

Water-repellent soils usually experience water flow impedance during the early stage of a wetting process followed by progressive increase of infiltration rate. Current infiltration models are not formulated to describe this peculiar process. Similarly, simplified methods of soil hydraulic characterization (e.g., BEST) are not equipped to handle water-repellent soils. Here, we present an adaptation of the BEST method, named BEST-WR, for the hydraulic characterization of soils at any stage of water-repellency. We modified the Haverkamp explicit transient infiltration model, included in BEST for modeling infiltration data, by embedding a scaling factor describing the rate of attenuation of infiltration rate due to water repellency. The new model was validated using analytically generated data, involving soils with different texture and a dataset that included data from 60 single-ring infiltration tests. The scaling factor was used as a new index to assess soil water repellency in a Mediterranean wooded grassland, where the scattered evergreen oak trees induced more noticeable water repellency under the canopies as compared to the open spaces. The new index produced results in line with those obtained using the water drop penetration time test, which is one of the most widely test applied for quantifying soil water repellency persistence. Finally, we used BEST-WR to determine the hydraulic characteristic curves under both hydrophilic and hydrophobic conditions.
Seasonal Tropical Cyclone Forecasts for the Middle America
Authors: Vargas Hernandez Felipe , Dominguez Sarmiento Christian
Published: March 2022

Tropical Cyclones (TCs) from the Eastern Pacific (EP) and North Atlantic (NA) Ocean commonly make landfall in the continental landmass of Middle America. These meteorological phenomena not only can cause floods and socioeconomic impacts, but they can also transport such heavy amounts of water that one event refill lakes, rivers, aquifers, and dams up to 100% during periods of prolonged droughts in arid and semiarid regions. This water resource can be used for agricultural and livestock activities, which are essential for Mexico and Central America’s countries. That is why local decision-makers are interested in having seasonal forecasts of tropical cyclone activity for the region. Current seasonal forecasts of tropical cyclone activity only focus on providing a number of TCs for the whole basin. However, local decision makers need information about possible affected regions at least 2 months in advance of the TC season peak (July-August-September for EP and August-September-October for the NA). This work is aimed at exploring a statistical-dynamical method for creating a seasonal forecast of TCs for Middle America.  We track TC-like vortices in five Coupled Global Models:  ECMWF, Météo-France, UKMO, DWD and CMCC during the 1993-2015 period (climatology period) and using two initial conditions: 1st July and 1st August for a three-month forecast. Our preliminary results show that three of the five models have the skill to adequately forecast the standardized track density anomaly and the TC activity per tercile (above-normal, normal, and below-normal) over the EP and NA basins. However, most of the models overestimate the activity. as indicated by the Brier Score (BS) and the Ranked Probability Skill Score (RPSS). Additionally, we present a statistical analysis of the type of tracks that are more important for the region and discuss how these types of tracks can be predicted depending on ENSO phase. We conclude that some models are useful to predict the TC activity 3 months in advance (dynamical approach), which can be combined with a statistical approach to provide more information about the type of TC track and possible affected regions.
An analogue approach to predicting European climate
Authors: Borchert Leonard , Menary Matthew , Mignot Juliette
Published: March 2022

Decadal climate prediction is a scientific endeavour of potentially large societal impacts. Yet such predictions remain challenging, as they predict climate skilfully only under certain circumstances or in specific regions. Moreover, decadal climate prediction simulations rely on dedicated coupled climate model simulations that are particularly expensive. In this study, we build upon earlier research by Menary et al. (2021) in search of a method to make skilful and cheap decadal climate predictions by constructing predictions from existing climate model simulations using the so-called analogue method.

The analogue method draws on the idea that there is decadal memory in the climatic state at the start of a prediction. This method identifies the observed state of the climate system at the start of a prediction and then screens the archive of available model simulations for comparable climatic states. It then selects a number of modelled climate states that are similar to the observed situation, and uses the years after the selected simulated climate states as prediction. Using a simple analogue method based on temperature trends in the North Atlantic basin, Menary et al. (2021) demonstrated skilful prediction of North Atlantic SST on par with dynamical decadal prediction simulations. In this study, we refine the original method by using more sophisticated algorithms to select the analogues, and choosing decadal prediction of seasonal European climate as our target. These new selection algorithms include multivariate regression at different time lags as well as non-linear methods.

 

Menary, MB, J Mignot, J Robson (2021) Skilful decadal predictions of subpolar North Atlantic SSTs using CMIP model-analogues. Environ. Res. Lett. 16 064090. https://doi.org/10.1088/1748-9326/ac06fb
Modelling decisions: a quantification of their influence on model results
Authors: Remmers Janneke , Teuling Ryan , Melsen Lieke
Published: March 2022

Scientific hydrological modellers make multiple decisions during the modelling process, e.g. related to the calibration period and temporal resolution. These decisions affect the model results. Modelling decisions can refer to several steps in the modelling process. In this study, modelling decisions refer to the decisions made during the whole modelling process, beyond the definition of the model structure. This study is based on an analysis of interviews with scientific hydrological modellers, thus taking actual practices into account. Six modelling decisions were identified from the interviews, which are mainly motivated by personal and team experience (calibration method, calibration period, parameters to calibrate, pre-processing of input data, spin-up period, and temporal resolution). Different options for these six decisions, as encountered in the interviews, were implemented and evaluated in a controlled modelling environment, in our case the modular modelling framework Raven, to quantify their impact on model output. The variation in the results is analysed using three hydrological signatures to determine which decisions affect the results and how they affect the results. Each model output is a hypothesis of the reality; it is an interpretation of the real system underpinned by scientific reasoning and/or expert knowledge. Currently, there is a lack of knowledge and understanding about which modelling decisions are taken and why they are taken. Consequently, the influence of modelling decisions is unknown. Quantifying this influence, which was done in this study, can raise awareness among scientists. This study pinpoints what aspects are important to consider in studying modelling decisions, and can be an incentive to clarify and improve modelling procedures.
Occurrence of discontinuities in the total ozone from ERA-5 reanalyse
Authors: Krizan Peter
Published: March 2022

The aim of this presentation is to search for the occurrence of discontinuities in the total ozone data from the ERA-5 reanalyse, with the help of the Pettitt, Buishand and the Standard homogeneity tests.   This occurrence is important for trend analyses, because the presence of discontinuities influences the values of trends and their significance. Discontinuities arise from the changing in the assimilation procedure, introducing new observation to the reanalyse, and changing of data quality. We search for their spatial, temporal and geographical occurrence. There are dates which the occurrence of discontinuities is expected in: 2004- transition from SBUV to EOS Aura data and 2015-  the 4.2 MLS data were started to use instead of version 2.2. We search for discontinuities in the following classes of extremity: 1st, 10th, 25th, 50th,75th,90th and 99th percentile as well as the mean. Generally speaking, the discontinuities are occurred approximately from 30 to 60 % of all grid cells.  The results are slightly test dependent and the Pettitt test is not able to detect the discontinuities in 2015.The best performance in discontinuity detection in this year was obtained for the Standard homogeneity test. Ozone data with high occurrence of the discontinuities is not suitable for trend analyses.   