bluuebunny/crossref_metadata_2025 huggingface dataset:
Gridding of high-frequency radar velocities using the Data-Interpolation Variational Analysis in n dimensions (DIVAnd)
Authors: Troupin Charles , Barth Alexander , Alba Marco , Novellino Antonio
Published: March 2022

The main goal of this work is to present the design and the implementation of a procedure for the reconstruction of surface velocity fields in different coastal regions of Europe, by applying advanced spatio-temporal interpolation techniques on high-frequency radar (HFR) radial velocities.

The method allows us to take additional constraints such as the boundary constraint (impermeability of the coastline), low divergence, or Coriolis effect. The procedure is applied to different coastal regions and the files obtained from the EMODnet Physics Thredds server. The follows steps:

Specification of the region of interest (rectangular bounding box, in the form), based on the coverage of the different radials.

Preparation of a high-resolution bathymetry for the region.

Setting of the period of interest (initial and final dates).

Setting of the analysis parameters: correlation length (longitude, latitude and possibly time), noise-to-signal ratio, relative importance of the constraint (divergence, boundary, Coriolis).

Specification of the metadata in the netCDF files.

Run of the interpolation.

Writing the netCDF files storing the results.

This procedure was applied to the Gulf of Manfredonia (Adriatic coast of Italy), the Gulf of Trieste (north of the Adriatic Sea), the Gulf of Naples (south-western coast of Italy) and the Gran Canaria island (Atlantic Ocean). 

The different parameters are optimised using a cross-validation technique: 

The radial velocities from one of the antennas are discarded.

The velocity field is reconstructed using the radial velocities from the remaining sites.

The velocity field is interpolated at the location of the discarded measurements and projected on the radial direction.

The RMS difference between the original (discarded) radial and the radial obtained in the previous step is computed.

The outputs (gridded fields) are provided as netCDF files following the Climate and Forecast (CF) conventions and the recommendation of the EuroGOOS HFR Task Team.

For the validation and intercomparison, different approaches are used: in the Gulf of Manfredonia, high-resolution satellite images of chlorophyll concentrations are used to derive the currents with the outputs of the HFR gridded fields; for the Gran Canaria system, we compared the velocity with the outputs of the IBI model (Atlantic-iberian Biscay Irish- Ocean Physics Analysis And Forecast, product IBI_ANALYSISFORECAST_PHY_005_001), provided by the Copernicus Marine Environment Monitoring Service.
Multidecadal Marine Heat Wave Variability in the Mediterranean
Authors: Licer Matjaz , Zunino Serena , Canu Donata
Published: March 2022

Marine heatwaves (MHW) have emerged as critical factors driving shifts and negative impacts on marine ecosystems and to ecosystem services. MHW frequency and severity is expected to increase in response to climate change and there is a need to assess the effect of past MHW on marine ecosystems in order to better understand future trends and impacts.

The aim of this work is provide a long term downscaled analysis of the Mediterranean MHW and cold spells (MCS) at 0.05° spatial resolution, and to further focus this analysis to four specific domains (Northern Adriatic, Ligurian Sea, Gulf of Lion, Catalan Sea) and 43 coastal locations in the Mediterranean basin. This analysis can be used to explore the links with other environmental and ecological data. 

Multidecadal L4-gridded satellite SST measurements are used to analyze statistical properties of MHW and MCS in the Mediterranean basin from 1989 until present. Methodology from Hobday et al. (2016, 2018) is used for the analysis. For each of the locations, cumulative MHW and MCS intensities are aggregated by year. All locations indicate a steep rise of MHW cumulative intensity and a sharp decline of MCS. Generalized extreme value analysis is performed to estimate multidecadal variability of SST anomaly return periods. Results show that at all locations a given return period gets associated with more and more extreme SST anomalies as time progresses.
Methodologies for the characterisation of spatially distributed hydrological events: the Italian case study.
Authors: Borre Alessandro , Viglione Alberto , Gabellani Simone , Ghizzoni Tatiana
Published: March 2022

Evaluating historical extreme flood events is fundamental due to their socioeconomic impacts. In this context, the spatial distribution of the event has a key role and the univariate approach, based on the analysis of local flood frequency on a single site, is not the proper one.

For this reason, in the recent past, an increasing amount of research has focused on the regional characterization of flood events, trying to describe their temporal and spatial distribution. The main objective of this work is the comparison of two different methods widely used for the selection and characterization of spatially distributed flood events for risk assessment purposes. Both methods were applied to the Italian territory and compared in terms of parameters used, results obtained, and technical analogies and differences. 

The two methodologies reveal similar results, comparable with a list of extreme events produced as a collection of historical flood reports. The results show that floods co-occurring in several basins are unevenly distributed, with a higher number of selected events occurred in Northern and Central Italy, where the largest Italian basins are located.
Belowground networking: Biogeography of EcM fungi and species variation at different woodland ages
Authors: Azevedo Olivia , van der Linde Sietse , Park Kirsty , Ashwood Frank , Fuentes-Montemayor Elisa , Wilson Clare , Watts Kevin , Vanguelova Elena
Published: March 2022

Ectomycorrhizae (EcM) are evolved mutualistic associations between soil fungi and plant roots. It has been shown that there can be species-specific differences in the ability to colonise roots. Colo­nised roots have increased longevity, greater resistance to pathogens, toxic elements in the soil and extreme con­ditions of temperature, acidity and moisture.

EcM inocula are an essential resource in forest management. Nevertheless, measures being implemented worldwide to promote forest cover recovery to reduce atmospheric CO2 levels can cause ecological shifts. Shifts to ecological communities take place as species become more or less abundant, are wiped out or colonise new habitats. However, these changes may not be captured by metrics focusing on species richness alone.

The lack of direct evidence of large-scale EcM temporal change in fungal community structure or function over time - commonly used in animal and plant research - is a basic, structural knowledge gap. Understanding temporal changes in community composition, whether via species losses and gains, or alterations to relative abundance and dominance is therefore essential to fathom the performance of terrestrial ecosystems, in particular the soil environment and its functions.

This study will characterise EcM fungi in woodland sites of varying ages. This study uses a space-for-time approach, benefiting from a collection of sites part of a wider study on the biodiversity responses to woodland planting.
Accumulation and alignment of elongated gyrotactic swimmers in turbulence
Authors: Jiang Linfeng , Liu Zehua , Sun Chao
Published: March 2022

Understanding the dynamics and transport of elongated gyrotactic swimmers in a flow is essential for the ecology of aquatic plankton. We study their dynamics in turbulence, whose orientation is governed by gravitational torque and local fluid velocity gradient. The gyrotaxis strength is measured by the ratio of the Kolmogorov time scale to the reorientation time scale due to gravity, and a large value of this ratio means the gyrotaxis is strong. By means of direct numerical simulations, we investigate the effects of swimming velocity and gyrotactic stability on spatial accumulation and alignment. Three-dimensional Voronoi analysis is used to study the spatial distribution and time evolution of the particle concentration. We study spatial distribution by examing the overall preferential sampling and where clusters and voids (subsets of particles that have small and large Voronoi volumes respectively) form. Compared with the ensemble particles, the preferential sampling of clusters and voids is found to be more pronounced. The clustering of fast swimmers lasts much longer than slower swimmers when the gyrotaxis is strong and intermediate, but an opposite trend emerges when the gyrotaxis is weak. In addition, we study the preferential alignment with the Lagrangian stretching direction, with which passive slender rods have been known to align. We show that the Lagrangian alignment is reduced by the swimming velocity when the gyrotaxis is weak, while the Lagrangian alignment is enhanced for the regime in which gyrotaxis is strong.
Estimation of simulation parameters for steady and transient 3D flow modeling at watershed scale
Authors: Latour Gillien , Horgue Pierre , Renard François , Guibert Romain , Debenest Gérald
Published: March 2022

Unsaturated water flows at watershed scale or Darcy-scale are generally described by the Richardson-Richards equation. This equation is highly non-linear and simulation domains are limited by computational costs. The porousMultiphaseFoam toolbox is a Finite Volume tool capable of modeling multiphase flows in porous media, including the solving of the Richardson-Richards equation. As it has been developed using the OpenFOAM environment, the software is natively fully parallelized and can be used on super computers. By using experimental data from real site with geographical informations and piezometrics values, an iterative algorithm is set up to solve an inverse problem in order to evaluate an adequate permeability field. This procedure is initially implemented using simplified aquifer model with a 2D saturated modeling approach. A similar procedure using a full 3D model of the actual site is performed (handling both saturated and unsaturated area). The results are compared between the two approaches (2D and 3D) for steady simulations and new post-processing tools are also introduced to spatialize the error between the two models and define the areas for which the behaviour of the models is different. In a second part, an optimization of the Van Genuchten parameters is performed to reproduce transient experimental data. The 3D numerical results at the watershed scale are also compared to the reference simulations using a 1D unsaturated + 2D satured modeling approach.
Exploring cirrus cloud microphysical properties using explainable machine learning 
Authors: Jeggle Kai , Neubauer David , Camps-Valls Gustau , Binder Hanin , Sprenger Michael , Lohmann Ulrike
Published: March 2022

Cirrus cloud microphysics and their interactions with aerosols remain one of the largest uncertainties in global climate models and climate change projections. The uncertainty originates from the high spatio-temporal variability and their non-linear dependence on meteorological drivers like temperature, updraft velocities, and aerosol environment. We combine ten years of CALIPSO/CloudSat satellite observations of cirrus clouds with ERA5 and MERRA-2 reanalysis data of meteorological and aerosol variables to create a spatial data cube. Lagrangian back trajectories are calculated for each cirrus cloud observation to add a temporal dimension to the data cube. We then train a gradient boosted tree machine learning (ML) model to predict vertically resolved cirrus cloud microphysical properties (i.e. observed ice crystal number concentration and ice water content). The explainable machine learning method of SHAP values is applied to assess the impact of individual cirrus drivers as well as combinations of drivers on cirrus cloud microphysical properties in varying meteorological conditions. In addition, we analyze how the impact of the drivers differs regionally, vertically, and temporally.

We find that the tree-based ML model is able to create a good mapping between cirrus drivers and microphysical properties (R² ~0.75) and the SHAP value analysis provides detailed insights in how different drivers impact the prediction of the microphysical cirrus cloud properties. These findings can be used to improve global climate model parameterizations of cirrus cloud formation in future works. Our approach is a good example for exploring unsolved scientific questions using explainable machine learning and feeding back insights to the domain science.
Reconciling South Asian Monsoon Rainfall and Wind Histories
Authors: Sarr Anta-Clarisse , Donnadieu Yannick , Bolton Clara , Ladant Jean-Baptiste , Licht Alexis , Fluteau Frédéric , Laugié Marie , Tardif Delphine , Dupont-Nivet Guillaume
Published: March 2022

Cenozoic evolution of South Asian Monsoon and mechanisms driving changes recorded in the geological record remain highly debated. An intensification of monsoonal rainfall recorded in sediment archives from the earliest Miocene (23-20 million years ago, Ma) is generally attributed to Himalayan uplift. However, Indian Ocean paleorecords place the onset of strong monsoons around 13 Ma, linked to strengthening of the Somali Jet that forces Arabian Sea upwelling.  In this contribution we reconcile these divergent records using Ocean-Atmosphere and ocean biogeochemistry models. Our results show that factors forcing monsoon circulation versus rainfall are decoupled and diachronous : Asian topography predominantly controlled early Miocene rainfall patterns, with limited impact on ocean-atmosphere circulation. Yet the uplift of East African and Middle Eastern topography played a pivotal role in the establishment of modern Somali Jet structure above the western Indian Ocean, while strong upwelling initiate in response to the emergence of the Arabian Peninsula. Our results emphasize a polygenetic history of the South Asian Monsoon with multiple paleogeographic controls: although elevated rainfall seasonality was likely a persistent feature since the India-Asia collision in the Paleogene, the modern-like monsoonal atmospheric circulation was only reached recently, in the late Neogene.
Mesoscale organisation transition during the 2nd Feb EUREC4A case study simulated by a high-resolution weather model
Authors: Saffin Leo , Marsham John , Blyth Alan , Parker Doug
Published: March 2022

Tropical shallow convection exhibits strong variations in mesoscale organisation. Bretherton and Blossey (2017) used an LES to show how this convective organisation can be produced due to an advective feedback with mesoscale vertical motion and adjustment to a weak temperature gradient. Narenpitak et al. (2021) used an LES with forcings following a boundary-layer trajectory to simulate a case study from the EUREC4A field campaign where the clouds transition from disorganised small cumulus (sugar) to deeper more organised clouds with large detrainment layers (flowers). The LES produced a transition in cloud organisation and the main driving process was shown to be the advective feedback in mesoscale vertical motion seen in Bretherton and Blossey (2017).For comparison, we have looked at the same case study using high-resolution nested simulations with the Met Office's weather model, the UM. The UM reproduces the transition from sugar to flowers. Consistent with Narenpitak et al. (2021), the UM shows that the transition is associated with an increase in organisation and the mesoscale advective feedback is an important driving process. However, unlike the LES, the UM simulations show that the sugar clouds are already associated with a large amount of organisation. Because the mesoscale organisation is already present in the UM, the advective dispersion of mesoscale aggregation is an important process opposing aggregation during the transition from sugar to flowers, unlike in the LES.
Squall line sensitivity in LES simulations
Authors: Groot Edward , Tost Holger
Published: March 2022

Upper tropospheric (UT) divergence is potentially an important mediator between convective scale error growth and advective/non-linear large scale error growth at jet stream scales (Baumgart et al. 2019). To investigate possible mechanistic links of error growth from small convective scales to the synoptic scales, but also to gain insight in convective processes and their (representation) uncertainty, we have compared UT divergence in an array of idealized LES-simulations of convective systems with different degree of organisation.

Using ensemble and physics perturbations, we have found that isolated convective systems roughly seem to obey the expected near-linear relationship between latent heating and mass divergence, but squall lines are found to be anomalous in this sense. At the same time, large intrinsic variability among squall lines with extremely similar initial conditions and unperturbed physics is explored in much detail. A link between the squall line anomaly and amount recirculated updraft air into the cold pool and its possible role in latent heat consumption is tested. Furthermore, the origin of squall line variability is investigated in depth.
Variability of the air-sea CO2 exchange in the Strait of Gibraltar based on measurements from a VOS line.
Authors: Curbelo Hernández David , Santana Casiano Juana Magdalena , González González Aridane , González Santana David , González Dávila Melchor
Published: March 2022

The spatio-temporal variability of the surface CO2 system and its air-sea fluxes were studied in the Strait of Gibraltar based on high-resolution underway field data collected between February 2019 and March 2021 by a surface ocean observation platform (SOOP) aboard a volunteer observing ship (VOS). The surface CO2 distribution was strongly influenced by the seasonal and spatial variability in the depth of the Atlantic-Mediterranean Interface layer and by upwelling of deep-water drove by the tidal and easterly winds. The variability of the CO2 fugacity (fCO2,sw) and fluxes were mainly driven by temperature despite the significant influence of non-thermal processes in the southernmost part. The thermal to non-thermal effect ratio (T/B) reached higher values values in the northern section (>1.8) compared with the southern section (<1.30) due to the enhancement of biological activity and vertical mixing related to the seasonal wind-induced upwelling along the African coast. The fCO2,sw increased with temperature by 9.02 ± 1.99 µatm ºC (r2=0.86) and 4.51 ± 1.66 µatm ºC (r2=0.48) in the northern and southern sections, respectively. The annual cycle (referenced to 2019) of total inorganic carbon normalized to a constant salinity of 36.7 (NCT) was attended. The net community production processes described 93.5-95.6% of the total NCT change, while the contribution of air-sea exchange and horizontal and vertical advection was found to be minimal (<4.6%). According to the seasonality of air-sea CO2 fluxes, the region behaved as a strong CO2 sink during the cold months and as a weak CO2 source during the warm months. The Strait of Gibraltar acted as annual net CO2 sink, with higher net ingassing along the southern section (-1.01 mol C m-2) compared to the northern section (-0.82 mol C m-2). The calculated average CO2 flux for the entire area was -7.12 Gg CO2 yr-1 (-1.94 Gg C yr-1).

Keywords: Air-sea CO2 fluxes, CO2 system, VOS line, Surface Ocean Observation Platform, Strait of Gibraltar.
Epistemic uncertainty in fault geometry effects earthquake rupture behavior
Authors: Zielke Olaf , Aspiotis Theodoros , Mai Paul Martin
Published: March 2022

It is well established in the seismology community that geometric complexity plays an important role for a fault’s seismotectonic behavior. It affects the initiation, propagation and termination of an earthquake as well as influencing the stress-slip relationship, the size of fault segments, and the probability of multi-segment rupture. Consequently, fault geometric complexity is studied intensively and increasingly incorporated into computational earthquake rupture simulations. These efforts reveal a problem: While we may be able to constrain a natural fault’s geometry with a high level of detail at the surface (i.e., the fault trace), we cannot do the same for the buried portion of the fault -where most of the rupture takes place. How much does a fault’s seismotectonic behavior vary as a result of this epistemic uncertainty?

We address this question computationally with a physics-based multi-cycle earthquake rupture simulator (MCQsim), enabling us to investigate how (for example) earthquake recurrence, slip accumulation, magnitude-frequency distribution, and fault segmentation vary (looking at the entire fault as well as individual locations on the fault) as function of our insufficient knowledge about the fault’s geometric complexity. To simulate fault geometric complexity, we generate 2-D random fields, using the “random midpoint displacement” method (RMD), representing the fault’s non-planar, self-similar geometry. The advantage of using RMD is that it allows us to create a 2-D random field while also keeping one or more of the field’s edges at a prescribed value. Hence, this approach allows us to generate a random field to represent fault roughness while also allowing us to incorporate what is known about the fault geometry (i.e., the fault surface trace, representing one of the random field’s edges). In doing so, we can investigate how the aforementioned seismo-tectonic parameters vary as a function of fault roughness uncertainty.

For this purpose, we create 5000-year long earthquake catalogs for a 150x18km large strike slip fault that is parameterized by more than 40k fault cells (average cell size 0.07km^2), containing earthquakes with 3.5 < M < 7.8. We create these catalogs for 100 roughness realizations while keeping the simulated fault’s surface trace constant for all realizations. The results of these simulations will be presented in our presentation.
Towards species-level forecasts of drought-induced tree mortality risk
Authors: De Kauwe Martin , Sabot Manon , Medlyn Belinda , Pitman Andrew , Meir Patrick , Cernusak Lucas , Gallagher Rachael , Ukkola Anna , Rifai Sami , Choat Brendan
Published: March 2022

Predicting species-level responses to drought at the landscape scale is critical to reducing future uncertainty in terrestrial carbon and water cycle projections. We embedded a stomatal optimisation model in the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model. We parameterised the model for 15 canopy dominant eucalypt tree species representative of a broad precipitation gradient across South East Australia (mean annual precipitation range: 344–1424 mm yr-1). We conducted three experiments: (i) applying CABLE to the 2017–2019 drought in South East Australia; (ii) a 20% drier drought; and (iii) a 20% drier drought with a doubling of atmospheric carbon dioxide (CO2). We identified several drought hotspots across the ranges of E.viminalis, E.obliqua, E.globulus, E.saligna, and E.grandis. By contrast, CABLE simulated drought resilience in species that are found predominately in semi-arid areas such as E.largiflorens and E.populnea. We identified several key model assumptions (e.g., the degree of stomatal control) and sensitivities (e.g., the role of CO2 in ameliorating drought) that require future research. Our results represent an important step forward in our capacity to forecast the resilience of individual tree species, providing an evidence base for decision-making around the resilience of restoration plantings or strategies associated with achieving net-zero emissions.
Efficient usage of information for modeling precipitation extremes and large scale influence
Authors: Fauer Felix , Ulrich Jana , Rust Henning
Published: March 2022

Extreme precipitation is currently the biggest climate-change-related thread in middle Europe with flooding events leading to high death tolls and huge existential and financial losses. Evaluating the probabilities of these extremes can help preventing casualties and reducing impact consequences. Our analysis is based on Intensity-Duration-Frequency (IDF) curves which describe the major statistical characteristics of extreme precipitation events. They provide information on the probability of exceedance of certain precipitation intensities for a range of durations and can help to visualize how extreme the event for different durations is.  A popular way of evaluating return periods of extremes is to model the underlying distribution of block maxima with the Generalized Extreme Value (GEV) distribution. A core problem when modeling extremes is the scarce availability of data. This can be addressed by using the available data more efficiently. Therefore, including maxima from different measurement durations is useful for (1) gathering more information from the data and (2) estimating return periods for different time scales with a consistent modeling approach. Duration-dependence is implemented directly into the parameter estimation (Koutsoyiannis et al., 1998) and enables a consistent model, i.e. without quantile-crossing. We present a new parameterization of the duration-dependent GEV (d-GEV) that is more flexible with respect to long ranges of durations and is considering the different time scales on which extremes occur in winter and summer (Fauer et al., 2021). Applying the new model to the extreme rain event on 14 July 2021 in Ahrtal, Germany reveals that the event was most extreme on a time scale of 20-30 hours.

Investigating the impact of large-scale atmospheric flow on extremes will help to learn how extremes changed in the past and make projections about their change in the future. Large scale variables are incorporated into the model as covariates in generalized linear models for the d-GEV parameters. An ongoing study tests for the inclusion of NAO, a blocking index, monthly mean temperature, etc., as predictor variables. First results show a significant correlation (5%-level) between monthly precipitation maxima and NAO/blocking for some durations and some seasons. It will be analyzed whether this connection can be useful for modelling d-GEV parameters with large-scale variables.
Very-high resolution WRF mesoscale urban-modeling for a coastal complex terrain metropolitan area
Authors: Rostkier-Edelstein Dorita , Berkovic Sigalit , Chudnovsky Alexandra , Avisar David
Published: March 2022

Urban-weather forecasts are necessary for well-known applications such as air pollution and urban comfort predictions. In the past few years additional uses arose such as urban air traffic by drones and helicopters. All of these applications require high-resolution numerical weather-forecasts that need to include the effect of the urban canopy. While CFD and LES methods are necessary to provide detailed information about the flow at the street level, mesoscale forecasts are needed to provide their initial and boundary conditions.

This work presents very-high resolution (500-m grid size) WRF simulations over a coastal complex terrain metropolitan area, Haifa, Israel, which is prone to high pollution events.

The simulations include three approaches to simulate the impact of the city on the simulated urban weather:

Bulk parameterization; which corresponds to the default MODIS landuse categories of the WRF modeling system.

Detailed local urban-canopy information for the Haifa metropolitan area derived with the help of a GIS tools was used with the two following urban canopy modules:

The single-layer urban canopy (SLUCM) parametrization.

The multi-level layer urban- canopy parameterization, specifically the building-effect parameterization with building energy model (BEP-BEM).

We focused on a wide variety of synoptic-scale weather conditions that, among others, can lead to or worsen high pollution events. The simulations used ERA5 reanalyses for initial and boundary conditions. We explored the sensitivity of the simulated urban flow and heat island effect to the planetary boundary layer parameterizations (YSU and Boulac), and the urban canopy modeling. Due to the lack of specific anthropogenic-heat information for the Haifa area, we used crude estimations of the timing and desired temperatures for air-conditioning usage in the BEP-BEM parameterization, and a typical diurnal cycle of anthropogenic heat for the SLUCM parameterization (with estimation of the maximal heat loads following literature for cities in similar climate zones and with similar population).

The simulations were compared to near surface observations of wind, temperature and relative humidity within and outside the urban area, and to vertical soundings at the only launching location in Israel, Beit-Dagan. Objective verification scores as well as visual verification of 2D maps of the aforementioned variables demonstrate that the simulations reproduce the different mesoscale dynamics under very different synoptic conditions. The impact of the detailed urban modeling (BEP-BEM and SLUCM) without specific information on the anthropogenic-heat, is limited in this case.  
The Role of the Magnetic Rayleigh-Taylor Instability in Resolving the Solar Prominence/Filament Paradox
Authors: Jenkins Jack , Keppens Rony
Published: March 2022

Prominences and filaments are manifestations of magnetised, levitated plasma within the solar coronal atmosphere. Expanding on our previous 2.5D work presented in Jenkins & Keppens (2021), we will present a state-of-the-art magnetohydrodynamic simulation that yields the first fully 3D model to successfully unite the extreme-ultraviolet and Hydrogen-α prominence views that contain radial striations with the equivalent on-disk filaments comprised of finite width threads. Owed to the unprecedented resolution with which this simulation is carried out, we complete a full observational synthesis and provide predictions of exactly what the instruments associated with the upcoming Solar Orbiter and DKIST will observe. We then begin with an analysis of all hydromagnetic sources of the vorticity evolution and find the internal plasma dynamics to be consistent with the nonlinear development of the magnetic Rayleigh-Taylor instability. A further stability analysis that drops the strict, idealised mRTi initial conditions then enables us to tentatively characterise the preceding linear development as the general (quasi-) interchange gravitational instability. Our simulations and analyses show clearly how this universal interchange process operates, and how our results and conclusions finally unify the contradictory prominence/filament perspectives.
Pyrogenic carbon from wildfire or from the laboratory 
Authors: Sun Daquan
Published: March 2022

Wildfires remove well-developed vegetation but restore it from an ecological point of view, although they are often called disasters when their intensity and extent in forests are large. Thermochemical decomposition of organic material at high temperatures (200 - 750 °C) in the absence of oxygen (or any halogen) to decompose biosolids has been recognised as a method with numerous benefits for waste management, carbon sequestration and sustainable agriculture. The effects of pyrogenic carbon (PyC) from wildfire and from the laboratory are believed to be different. The evidence to date is informative in bridging pyrogenic carbon from wildfire and pyrolysis, including aspects of: 1) PyC as a microsite for microbial communities; 2) the role of PyC of different sizes in soil aggregation; 3) the role of the soil microbiome in soil aggregation; 4) nutrient release - phosphorus availability in PyC. Future work is needed to investigate 1) the role of nano- or micro-sized PyC in the guts of soil fauna - nutrient uptake and function of the microbiome; 2) linking municipal biowaste to carbon sequestration; 3) improving efficiency in composting and vermicomposting; and 4) negative impacts on soil fauna such as earthworms. Knowledge of PyC in materials science, waste management and environmental microbiology offers opportunities to make breakthroughs in biowaste management and climate change mitigation.
Extreme hydrometeorological events, a challenge for geodesy and seismology networks
Authors: Van Camp Michel , de Viron Olivier , Dassargues Alain , Delobbe Laurent , Chanard Kristel
Published: March 2022

The use of seismometer and gravimeter captures complementary data and brings a new understanding of the July 2021 catastrophic floods in Belgium. A sudden increase in seismic noise coincides with the testimony reporting on a “tsunami” downstream of the Membach geophysical station, along the Vesdre valley. Concurrently, the gravimeter evidenced a rising saturation of the weathered zone, thus showing less and less water accumulation. When rain re-intensified after a 3-hour break, the saturated state of the subsoil induced an accelerated increase of the runoff, as revealed by the Vesdre River flow, in a much stronger way than during the rainy episodes just before. We show that a gravimeter can detect in real-time the saturation of the catchment subsoil and soil. This saturation resulted, when the rain re-intensified, in a sudden, devastating and deadly flood. This opens perspectives to use real-time gravity for early warnings of such events
Role of human impact on fire history and vegetation succession in one of the oldest protected forests in Europe
Authors: Kuosmanen Niina
Published: March 2022

Fire is naturally an integral part of the northern boreal forests dynamics. However, anthropogenic activity has greatly affected the fire history in Fennoscandia, especially during the last millennia and the effective fire suppression practically led to the absence of a natural fire regime in boreal forests in Finland. However, the changing climate conditions may increase the risk of severe fire events regardless of the fire management. Therefore, it is important to look into the long-term interactions between human impact, fire and vegetation succession in order to understand the possible future role of fire in boreal forests.

One of the oldest protected areas in Europe is located in Central Finland and provides a good opportunity to investigate the change from natural fire and vegetation dynamics to human controlled fire regime and the natural vegetation succession after cessation of the slash-and-burn cultivation. The site is known to have been under slash-and-burn cultivation until the beginning of the 19th century and the last known burnings were done in the 1840s after which the site has been left to natural succession. The site was partly protected in 1911 and it was included into national the old-growth forest reserve protection program in 1994.

In order to investigate the long-term natural fire history and the role of human impact in the fire and the vegetation dynamics during last 3000 years we collected peat cores covering from two small forest hollows from the Kuusmäki old-growth forests protected area. Macroscopic (> 150 µm) charcoal and Neurospora-fungal spores are used to reconstruct the fire history and pollen analysis is performed to reconstruct the long-term vegetation dynamics in the study area.

The preliminary results demonstrate an increase in charcoal abundance from 16th century suggesting increased fire activity and a more intensive period of slash and burn cultivation in the area until the beginning of the 19th century. The absence of charcoal during the last century suggests absence of fire after the cessation of slash and burn cultivation. These results together with the vegetation succession will be further discussed in the presentation.
On the sources of long-term trends of airborne birch and grass pollen
Authors: Verstraeten Willem , Bruffaerts Nicolas , Kouznetsov Rostislav , Sofiev Mikhail , Delcloo Andy
Published: March 2022

Airborne pollen may have a substantial contribution to respiratory allergies affecting the public health badly, especially in combination with long-term exposure by other air pollutants. In some European countries the prevalence of people with pollinosis is up to 40%. In Belgium, ~10% is sensitive to birch pollen and ~15% to grass pollen. In the future, even more people might be affected since climate change and land-use change elicit an increased amount of allergenic airborne pollen and prolonged pollen seasons.

In this study we have used the pollen transport model SILAM (System for Integrated modeLling of Atmospheric coMposition) for attributing the long-term changes in the releases of pollen by birches and grasses to meteorology and vegetation dynamics. The pollen transport model is applied for Belgium and is driven by ECMWF ERA5 meteorological data in a bottom-up emission approach for the period 1982-2019. The corresponding maps with grass and birch pollen emissions sources, i.e. the dynamic vegetation component, are based on merging multi-decadal datasets of spaceborne NDVI with forest inventory data and grass distribution maps for 1982-2019. For each model gridcell we compute temporal trends based on the Theil Sen slopes and the Area Under the Curve (AUC) of the seasonal birch and grass pollen cycles based on daily pollen levels, and of the daily meteorological model input for the period 1982-2019. The gridcell based association between trends in pollen and meteorology are derived based on the Kendall correlation coefficient.

Our findings indicate that the increasing radiation, the decreasing precipitation and the decreasing horizontal wind speed are associated with a strong increase in birch pollen levels for the period 1982-2019. The decreasing grass pollen levels in the air over the same period are associated with decreasing precipitation. This is, however, induced by the decreasing trend in grass pollen sources. The associations between meteorology and airborne birch pollen levels are much stronger compared to grass pollen. The specific contribution of birch pollen production dynamics to the levels of birch pollen in the air is highly associated with wind speed and precipitation. By introducing the inter-seasonal variation in birch pollen production the overall increase rate is dampened with ~7%. In contrast, the grass pollen production dynamics resulted into 3.5 times less grass pollen in the air over the studied period.
7th February 2021 Chamoli (Uttarakhand, India) Rock-ice Avalanche: Numerical Model Simulated Prevailing Meteorological Conditions
Authors: Srivastava Piyush , Namdev Prabhakar , Singh Praveen Kumar
Published: March 2022

The present study aims to analyze the high-resolution model-simulated meteorological conditions during the Chamoli disaster, Uttarakhand, India (30.37°N, 79.73°E), which occurred on 7th February 2021. The Weather Research and Forecasting (WRF) model is used to simulate the spatiotemporal distribution of meteorological variables pre and post-event. The numerical simulations are carried out over two fine resolution nested model domains covering the Uttarakhand region over a period of 2 weeks (2nd February to 14th February 2021). The model simulated meteorological variables, e.g., air temperature, surface skin temperature, turbulent heat flux, radiative fluxes, heat and momentum transfer coefficients, specific humidity, and upper wind patterns are found to show significant departure from their usual pattern starting from 72 h until a few hours prior to the Chamoli rock-ice avalanche event. The average 2-m air and skin temperatures near the rock-ice avalanche site 48 h prior to the event are found to be much lower than the average temperatures post-event. The total turbulent heat flux mostly remained downward (negative) throughout 72 h prior to the event and was found to have an exceptionally large negative value just a few hours before the rock-ice avalanche event. Model simulated rainfall and Global Precipitation Measurement Mission (GPM, IMERG) derived rainfall suggest that the part of the Himalayan region falling in the simulation domain received a significant amount of rainfall on 4th February, ~ 48 h prior to the event, while the rest of days prior and post-event mostly remained dry. 
The assessment of minor tidal constituents in ocean models for optimising the ocean tidal correction
Authors: Hart-Davis Michael , Sulzbach Roman , Dettmering Denise , Thomas Maik , Schwatke Christian , Seitz Florian
Published: March 2022

Satellite altimetry observations have provided a significant contribution to the understanding of global sea surface processes, particularly allowing for advances in the accuracy of ocean tide estimations. Accurate estimations of ocean tides are valuable for the understanding of sea surface processes from along-track satellite altimetry. Ocean tide models have done a suitable job in providing these estimations, however, difficulties remain in the handling of minor tidal constituents. The estimation of minor tides from altimetry-derived products proves difficult due to the relatively small signals of these tides and due to the temporal sampling of the altimetry missions meaning a long time series of observations is required. This is generally solved by models and tidal prediction software by using admittance theory to infer these minor constituents from the more well-known and better estimated major constituents. In this presentation, the results of a recent study that looked at the estimation of several minor constituents directly from tide models compared to the inferred version of these tides are presented. The model used for the direct estimations and the inferences is a regional version of the Empirical Ocean Tide model (EOT) which is a data-constrained model derived from multi-mission satellite altimetry. The resultant estimations from these two approaches are compared to two global numerical tide models (TiME and FES2014) and in situ tide gauge observations (from the TICON dataset). Based on the study of eight tidal constituents, a recommendation of directly estimating four tides (J1, L2, μ2 and ν2) and inferring four tides (2N2, ϵ2, MSF and T2) is given to optimise the ocean tidal correction. Following on from this, a new approach of merging tidal constituents from different tide models to produce the ocean tidal correction for satellite altimetry that benefits from the strengths of the respective models is presented. This concept allows for the benefit of using data-constrained tide models in the estimation of the major constituents as well as the use of numerical models in providing a greater number of minor constituents, to be combined to provide a more optimised estimation of the full tidal signal.
Stability analysis of check dam impacted by intermittent surge
Authors: Liu Daochuan , Xiang Bo , Shao Jiang , He Yunyong , Liang Miao
Published: March 2022

Viscose debris flows always move in the manner of intermittent surges and show obvious fluctuation. In the traditional design of debris flow control engineering, the impact of single surge has on the check dams was the only factor to be taken into consideration. Whereas stability variation law of the check dams under the impact of intermittent surges was always neglected. On the basis of debris flow observation material from the Jiangjia Gully (JJG), we initially analysis the fluctuating and decaying characteristics of intermittent surges. Results indicate that intermittent surges exhibit obvious decaying characteristics and finally decay in a power-law form, showing a strong no-linear behavior. Next, based on loading combination and stability analysis of check dams, we deduced the expression of the stability coefficient when intermittent surges impact on the check dams in empty and half reservoir conditions. Meanwhile, stability variation law of the check dams in the different conditions were compared. Results indicated that when intermittent surges impact on check dams, anti-sliding stability coefficient (Kc) and anti-overturning stability coefficient (Ky) decrease with the increase of surges, and the former 3th~5th surges experienced the largest decaying rate. On the other hand, the deeper deposits in the reservoir corresponds to the smaller stability coefficient under the impact of the same intermittent surges. Finally, the relationship between flow depth and stability coefficients is in the form of an envelope curve, inferring that the variation of flow depth restraint the stability coefficient of check dams.
Update on soil carbon balance in Hungarian crop rotation systems
Authors: De Luca Giulia , Pintér Krisztina , Fóti Szilvia , Nagy Zoltán , Balogh János
Published: March 2022

Long term flux measurements are needed to improve our understanding of the carbon balance of arable lands. The objective of our study was to determine the seasonal dynamics of carbon cycling in a Hungarian cropland and to examine the effect of crop rotation on net ecosystem exchange of CO2 (NEE), furthermore to assess the influences of C outputs and inputs derived from lateral fluxes on soil organic carbon (SOC) stock. In this study we update the results presented in our poster of last year’s conference (EGU21-10977).

The experiment began in 2017 and crop rotation of the measured field consisted of winter wheat (2017-2018 and 2019-2020), rapeseed (2018), sorghum (2019) and sunflower (2021). CO2 fluxes and annual net ecosystem exchange (NEE) of CO2 were measured by a field-scale eddy covariance (EC) station at a Central Hungarian cropland site. Both vertical and lateral C fluxes were taken into account when calculating the net ecosystem carbon budget (NECB).

As presented in our previous study the largest sink activity was observed in the sorghum season (-277 g C m-2 from sowing to harvest). The cropland acted as a source of CO2 during the rapeseed season (140 g C m-2) due to incomplete germination caused by extreme autumnal drought.

We found that during the study period both meteorological variables and lateral carbon fluxes such as C inputs derived from seed and crop residues and outputs (harvest) had significant influence on the C dynamics. The higher temperatures and precipitation amount that characterised the fall of 2019 caused large differences in NEE dynamics for winter wheat when compared to 2017. The impact of climatic factors could be seen in the sunflower period since lack of precipitation in 2021 led to remarkably low carbon uptake.

Fallow periods in total covered a relatively long period of time (approximately 1 year out of the 4 year long study period). These fallow periods had a significant effect on NECB values due to immense C loss. During the four years of our experiment cumulative NEE was -222 g C m-2 and NECB was 726 g C m-2 as carbon loss during fallow periods (437 g C m-2 in total) and carbon export through harvest (964 g C m-2 in total) counterbalanced the crop’s CO2 uptake.

We can conclude that while this Hungarian cropland was a sink of carbon it could not maintain the soil organic carbon content as it was not able to sequester enough carbon to do so. Cover plants and crop residue retention could be a solution to reduce the risk of soil carbon stock depletion but further studies are needed in the field of soil management practices.