bluuebunny/crossref_metadata_2025 huggingface dataset:
Meteorological and hydrological conditions triggering rockfall events in Germany
Authors: Nissen Katrin , Rupp Stefan , Guse Björn , Ulbrich Uwe , Vorogushyn Sergiy , Damm Bodo
Published: March 2021

In this study we present the results of a logistic regression model aimed at describing changes in probabilities for rockfall events in Germany in response to changes in meteorological and hydrological conditions.

The rockfall events for this study are taken from the landslide database for Germany (Damm and Klose, 2015). The meteorological variables we tested as predictors for the logistic regression model are daily precipitation from the REGNIE data set (Rauthe et al. 2013), hourly precipitation from the RADKLIM radar climatology (Winterrath et al., 2018) and temperature from the E-OBS data set (Cornes et al., 2018). As there is no observational soil moisture data set covering the entire country, we used soil moisture modelled with the state-of-the-art hydrological model mHM (Samaniego et al. 2010), which was calibrated using gauge measurements.

In order to select the best statistical model we tested a large number of physically plausible combinations of meteorological and hydrological predictors. Each model was checked using cross-validation. The decision on the final model was based on the value of the logarithmic skill score and on expert judgement.

The final statistical model includes the local percentile of daily precipitation, total relative soil moisture and freeze-thawing cycles in the previous weeks as predictors. It was found that daily precipitation is the most important parameter in the model. An increase of daily precipitation from its median to its 80th percentile approximately doubles the probability for a rockfall event. Higher soil moisture and the occurrence of freeze-thaw cycles also increase the probability for rockfall events. 

Cornes, R. C. et al., 2018: An ensemble version of the E‐OBS temperature and precipitation data sets. Journal of Geophysical Research: Atmospheres, 123, 9391– 9409.

Damm, B., Klose, M., 2015. The landslide database for Germany: Closing the gap at national level. Geomorphology 249, 82–93

Rauthe, M. et al., 2013: A Central European precipitation climatology – Part I: Generation and validation of a high-reso-lution gridded daily data set (HYRAS), Vol. 22(3), p 235–256.

Samaniego, L. et al., 2010: Multiscale parameter regionalization of a grid-based hydrologic model at the mesoscale. Water Resour. Res., 46,W05523

Winterrath, T. et al., 2018: RADKLIM Version 2017.002: Reprocessed gauge-adjusted radar data, one-hour precipitation sums (RW), DOI: 10.5676/DWD/RADKLIM_RW_V2017.002.
Assessment of Climate Suitability for Prunus armeniaca L. in Turkey in a Changing Climate
Authors: An Nazan , Turp M. Tufan , Kurnaz M. Levent
Published: March 2021

Climate is a crucial factor for agricultural production and productivity. Foreseeing climate change in the future means predicting the possible effects on agriculture, and such studies observing year-dependent variability and predicting the effects of the near and mid-future climate change are valuable for both food security and economic value especially for countries which have commercial agricultural products like Turkey, as a Mediterranean Basin country with significant agricultural diversification. Apricot (Prunus armeniaca L.), which is one of Turkey's most important export products are expected to be affected significantly by climate change. Therefore, it is very important to see whether it will grow in the same regions in the future due to climatic changes for apricot. Hereunder, high resolution climate data, as an input for the membership function to be applied for classification of the climate suitability index, were obtained from RegCM4.4 under the RCP8.5 scenario for the period of 2021-2050 v.s. 1991-2018 for different phenological periods. Briefly, results indicate that adverse changes in climate suitability conditions for current apricot growing locations, 48 locations in the study, and the number of climate suitable locations for apricot will significantly decreases in the near and mid-future.  

 

 

Acknowledgement: This research has been supported by Bogazici University Research Fund Grant Number 17601.
www.drought.ch – A 10-year span from technology readiness level 1 to 8
Authors: Zappa Massimiliano , Bernhard Luzi , Brunner Manuela I. , Bogner Konrad , Liechti Katharina , Lustenberger Florian , Spirig Christoph , Seidl Irmi , Staehli Manfred
Published: March 2021

Up to 2003, a collective memory on severe drought-events in Switzerland has been pretty much inexistent. There has been no targeted research on hydrological drought and no early detection instrument was available for guiding decision makers. Research within the framework of the National Research Program 61 (www.nrp61.ch) “Sustainable Water Use” (2010-2013) provided the cornerstones for prototyping the early drought detection platform www.drought.ch. In June 2013, the platform was launched and provided useful information during two severe drought events in 2015 and 2018. At the same time, awareness about future increases in the frequency of such events has been confirmed by several studies considering future streamflow projections. Drought and water scarcity are now found on the list of the most threatening hazards for Switzerland. Several political initiatives call for increased efforts in the deployment of a national early warning system for critical droughts. This led to the proposition, that www.drought.ch should be integrated as the main tool for official national drought warnings in Switzerland.

This contribution summarizes the 10-year process of developing the drought warning system drought.ch from technology readiness level 1 (TRL 1, “basic principles observed”) to TRL 8 (“system complete and qualified”). TRL1 started in 2010 with a two-stage dialogue with stakeholders from different sectors including national administration, hydropower, forestry, agriculture, and river navigation. TRL 3 (“experimental proof of concept”) began in 2013. Over the years, the initial focus on drought-specific monitoring of precipitation, streamflow, lake levels, groundwater levels, soil moisture deficit, snow resources, and dryness in forests and stream temperatures has been expanded to advanced countrywide sub-seasonal ensemble prediction of drought-parameters. The last major upgrade was the deployment of monthly forecasts (issued twice a week) during the extreme summer drought in 2018. Analyses of public drought perception after the 2018 event demonstrated that TRL 8 has been achieved, i.e. that the drought platform is useful.

 
Seasonal trends of reservoir-triggered seismicity in Song Tranh 2 reservoir, Vietnam
Authors: Lizurek Grzegorz , Leptokaropoulos Konstantinos , Wiszniowski Jan , Nowaczyńska Izabela , Van Giang Nguyen , Plesiewicz Beata , Quoc Van Dinh
Published: March 2021

Reservoir-triggered seismicity (RTS) is the longest known anthropogenic seismicity type. It has the potential to generate seismic events of M6 and bigger. Previous studies of this phenomenon have proved that major events are triggered on preexisting major discontinuities, forced to slip by stress changes induced by water level fluctuations and/or pore-pressure changes in the rock mass in the vicinity of reservoirs. Song Tranh 2 is an artificial water reservoir located in Central Vietnam. Its main goal is back up the water for hydropower plant. High seismic activity has been observed in this area since the reservoir was first filled in 2011. The relation between water level and seismic activity in the Song Tranh area is complex, and the lack of clear correlation between water level and seismic activity has led to the conclusion that ongoing STR2 seismic activity is an example of the delayed response type of RTS. However, the first phase of the activity observed after impoundment has been deemed a rapid response type. In this work, we proved that the seismicity recorded between 2013 and 2016 manifested seasonal trends related to water level changes during wet and dry seasons. The response of activity and its delay with respect to water level changes suggest that the main triggering factor is pore pressure change due to the significant water level changes observed. A stress orientation difference between low and high water periods is also revealed. The findings indicate that water load and related pore pressure changes influence seismic activity and stress orientation in this area.

This work was partially supported by research project no. 2017/27/B/ST10/01267, funded by the National Science Centre, Poland, under agreement no. UMO-2017/27/B/ST10/01267.
Sedimentary trace metals: improving proxies for deoxygenation in coastal European seas
Authors: Paul Mareike , van Helmond Niels A. G. M. , Slomp Caroline P. , Jokinen Sami A. , Virtasalo Joonas J. , Filipsson Helena L. , Jilbert Tom
Published: March 2021

Deoxygenation in response to eutrophication and climate change in coastal systems is increasing worldwide. Low oxygen conditions cause the chemical transformation of redox-sensitive trace metals (e.g. molybdenum and uranium) in seawater, and their subsequent transport to the sediment. Sedimentary trace metal contents can therefore be used as a record of changes in bottom water oxygen conditions allowing the history of deoxygenation to be reconstructed. However, most trace metal studies have focused on strongly reducing and sulfidic settings, leaving mildly reducing and oxygenated (but eutrophic) settings vastly understudied. Currently, it is unknown to what extent existing trace metal redox proxies are applicable to reconstruct oxygen conditions in coastal zones experiencing mild deoxygenation, despite the fact that such areas occupy vast stretches of the coastal oceans. Here, we study trace metal enrichments in 13 European coastal marine sites with varying bottom water redox conditions and depositional environments. Our data demonstrates that sedimentary molybdenum and uranium contents are sensitive to deoxygenation across a range of settings, although the mechanisms of enrichment may vary. Improved understanding of molybdenum and uranium dynamics in mildly reducing coastal settings will facilitate the development of reliable and widely applicable molybdenum and uranium-based redox proxies.
The partition coefficients of Nd and Sm for the sulphides: first data from Palaeoproterozoic layered Cu-Ni-PGE complexes of Fennoscandian Shield
Authors: Serov Pavel , Bayanova Tamara
Published: March 2021

The Sm-Nd systematics is one of the most demanded isotope-geochronological tools to study ancient geological complexes. With the accumulation of knowledge about the REE in various geological processes, the question arises of extending the capabilities of the Sm-Nd method by using new mineral geochronometers. The research focused on defining the time of the ore process and its position in the general geochronological scale of formation of the geological site become particularly important. There is a pressing need for defining possible forms of REE occurrence in a lattice of geochronometer minerals in the Sm-Nd study of accessory minerals (e.g. fluorite, burbankite, eudialite, ruthile, etc.) and ore minerals (ilmenite, chrome-spinellid, sulfide minerals). The Sm-Nd method of dating ore processes using sulphide minerals, successfully used on several geological objects, made it possible to determine the main stages of ore formation and confirm geochronologically the conclusions about the syngenetic or epigenetic nature of the ore process.

Pyrite, pentlandite, chalcopyrite and pyrrhotite from the main industrial fields of the Fennoscandinavian shield were studied: Monchegorsk pluton, Fedorovo-Pansky intrusion, Pechenga, Penicat intrusion and Ahmavaara (Finland). Using a mass-spectrometric method 35 sulphide monofractions were analyzed. The partition coefficients for Nd and Sm were established: for pyrite - 0.229 (Nd) and 0.169 (Sm); for pyrrhotite - 0.265 (Nd) and 0.160 (Sm); for chalcopyrite - 0.229 (Nd) and 0.161 (Sm); for pentlandite – 0.158 (Nd) and 0.082 (Sm). The mean values for DNd are 0.201, for DSm=0.145 and resulting DNd/DSm about 1.4.

Probably, the distribution of REE in sulfide minerals is inherited from fluids during sulfide formation. REE concentrations in sulphide may reflect the composition of the fluid.

Thus, for the first time data on Sm and Nd concentrations have been obtained by mass spectrometry. Coefficients of neodymium and samarium distribution in sulfides have been calculated for major Cu-Ni-PGE complexes of Fennoscandia.

 

This study performed under the theme of scientific research 0226-2019-0053 and were supported by the RFBR  18-05-70082.
Reconstructing LGM paleoglaciers and their ELAs along the southern fringe of the Eastern European Alps
Authors: Rettig Lukas , Ferrarese Francesco , Monegato Giovanni , Mozzi Paolo , Spagnolo Matteo
Published: March 2021

The reconstruction of paleoglaciers and specifically the calculation of their equilibrium line altitude (ELA) is an important source of quantitative paleoclimatic information in mountainous regions. During the Last Glacial Maximum (LGM), the prealpine massifs in the south-eastern part of the Alpine chain (Venetian Prealps, Carnic Prealps and Julian Prealps) hosted several small valley glaciers and local ice caps that were isolated from the larger ice-streams occupying the major valleys. Because of their small size and independent dynamics these glaciers can be considered as excellent indicators of local climatic conditions. Although this potential has long been recognised and the sediments and landforms related to these glaciations have been mapped in a few areas, a regional perspective on this type of glaciation is still lacking. This is primarily due to the wide range of methods of ELA reconstructions that has been applied historically, which makes a solid comparison between different localities difficult.

Here, we present a detailed re-evaluation of local LGM glaciation in the south-eastern Alps based on a large-scale survey of remote sensing data and targeted field work at selected localities. Recently developed GIS tools were applied for the reconstruction of paleoglacier geometries and ELAs (Pellitero et al. 2015, 2016). The obtained values are used both to discuss regional climatic patterns during the LGM and site-specific topographic factors. A specific focus is set on the Monte Cavallo group, where glacial sediments from the LGM are covering a thick sequence of interstadial lacustrine deposits. A set of new radiocarbon dates from this succession provides a first chronological control on the onset of glacier expansion in this part of the Alpine chain.

 

References:

Pellitero, R. et al. 2015. A GIS tool for automatic calculation of glacier equilibrium-line altitudes. Computers & Geosciences 82: 55-62.

Pellitero, R. et al. 2016. GlaRe, a GIS tool to reconstruct the 3D surface of palaeoglaciers. Computers & Geosciences 94: 77-85.
Interaction between equatorial stratospheric Kelvin waves and gravity waves in a QBO phase
Authors: Kim Young-Ha , Achatz Ulrich
Published: March 2021

An interaction between Kelvin waves and gravity waves (GWs) in the tropical stratosphere is investigated using the global weather-forecasting model ICON with a horizontal grid spacing of ~160 km. To represent GWs in ICON, the Multi-Scale Gravity Wave Model (MS-GWaM) is used as a subgrid-scale parameterization, which is a prognostic model that explicitly calculates the evolution of GW action density in phase space. The simulation is initialized on a day in the QBO phase of the easterly maximum at ~20 hPa, so that Kelvin waves can propagate vertically throughout the lower stratosphere during the simulation. We show that Kelvin waves with zonal-wind amplitudes of about 10 m s-1 can largely affect the distribution of GW drag, by disturbing the local wind shear. Moreover, due to the zonal asymmetry in the activity of tropospheric convection, which is the source of GWs in the tropics, this effect of Kelvin waves can also influence the zonal mean of GW drag. The effect seems to be large when a strong convective system, from which large-amplitude GWs are generated, propagates eastward in the troposphere together with a phase of stratospheric Kelvin wave aloft. In our case, such an interaction causes a zonal-mean GW drag of ~0.26 m s-1 d-1 at ~20 hPa for a week during an early phase of the easterly-to-westerly transition of the QBO. The result emphasizes the importance of a correct representation of large-scale waves as well as subgrid-scale GWs in QBO simulations.
Lightning Sferics for Lightning Location – Complex Analysis
Authors: Bai Xue , Fullekrug Martin
Published: March 2021

Lightning location networks commonly use the time stamps of the received radio waveforms from lightning flashes (sferics) at numerous stations to determine a single lightning flash location. In order to extract more information from the recorded lightning waveforms, a complex analysis of the received electromagnetic waves is investigated.  

The long term aim of this study is to use the complex radio waveforms from lightning flashes (complex sferics) to develop an interferometry technique that uses complex parameters inferred from each individual sample (Liu et al., 2018). In this work, the coherency of complex lightning sferics is investigated, which is a measurement of the phase information. Complex lightning sferics are not well understood such that an analysis strategy needs to be developed. We adapt here the idea of using a waveform bank (Said et al., 2010), which is composed of lightning sferics at predefined distances. Before generating the waveform bank, a rigorous quality check process is carried out to ensure a high data reliability for the selected lightning events. Both, the amplitude waveform bank and the coherency waveform bank are generated. The novelty of this work is that the coherency measurement is shown to be as valid as the amplitude measurement towards the characterisation of the received lightning waveforms at various distances. In particular, the coherency has the capability to detect more skywaves than the amplitude alone.  

The potential impact of this research for lightning detection and location networks is that this novel method is able to locate a single event in an area defined by the coherency distribution map when different combinations of the waveform time stamps are used (Füllekrug et al., 2016). In future work, the coherency distribution map of a single lightning event could be calculated, and a dynamic coherency map can be built on top of that. The dynamic coherency map is capable to reveal formation on propagation track of each storm, and may possibly be used for lightning forecasting.

 

References:

Füllekrug, M., Liu, Z., Koh, K., Mezentsev, A., Pedeboy, S., Soula, S., Enno, S.E., Sugier, J., and Rycroft, M.J. (2016), Mapping lightning in the sky with a mini array, Geophys. Res. Lett., 43, 10,448–10,454, doi:10.1002/2016GL070737.

Liu, Z., Koh, K.L., Mezentsev, A., Enno, S.E., Sugier, J., and Fullekrug, M. (2018), 

Lightning sferics: Analysis of the instantaneous phase and frequency inferred from complex waveforms. Radio Science, 53, 448– 457, doi:10.1002/2017RS006451.

Said, R.K., Inan, U.S., and Cummins, K.L. (2010), Long‐range lightning geolocation using a VLF radio atmospheric waveform bank, J. Geophys. Res., 115, D23108, doi:10.1029/2010JD013863.
Impact of atmospheric gravity waves on the Martian global water cycle during dust storms
Authors: Shaposhnikov Dmitry , Medvedev Alexander , Rodin Alexander , Hartogh Paul
Published: March 2021

Effects of atmospheric gravity waves (GWs) on the global water cycle in the middle and high atmosphere of Mars during the global dust storms (Martian years 28 and 34) have been studied for the first time using a general circulation model. Dust storm simulations were compared with those utilizing the climatological distribution of dust in the absence of a GW parameterization. The dust storm scenarios are based on the observations of the dust optical depth by the Mars Climate Sounder instrument on board Mars Reconnaissance Orbiter. The simulations show that accounting for the influence of GWs leads to a change in the concentration of water vapor in the thermosphere. The most significant effect of GWs is twofold. First, cooling of the thermosphere at the poles leads to a decrease in the water vapor abundance during certain periods. Second, heating in the regions representing the main channels of water supply to the upper atmosphere (the so-called water "pump" mechanism) increases, on the contrary, its concentration. Since the temperature increase provides more intensive atmospheric mixing, and also expands the supply channel through an increase in saturation pressure. The dynamic balance of these basic mechanisms drives the changes in the distribution of water vapor in the upper atmosphere. Dust storms enhance pumping of water vapor into the upper atmosphere. Seasonal differences in the storm occurrences in different years allow for tracking the paths of water vapor transport to the upper atmosphere.
Axial atmospheric Earth rotation excitation predicted from CMIP6 model simulations
Authors: Böhm Sigrid , Salstein David
Published: March 2021

One special component of the Coupled Model Intercomparison Project phase 6 (CMIP6) is the so-called ScenarioMIP. Different Earth system variables are provided within this project originating from numerous models and model runs operated by research centers around the globe. The models simulate future climate, based on alternative scenarios of future greenhouse gas emissions and land use changes linked to socioeconomic factors. The simulations, which cover the 21st century, use different forcings that are defined from a combination of possible future pathways of societal development, the Shared Socioeconomic Pathways (SSPs), and the Representative Concentration Pathways (RCPs), identified by what radiative forcing level might exist in 2100. In this study, we focus on the analysis of multi-model projections of zonal wind fields, stemming from historical simulations and from the four tier 1 alternate scenarios SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5. We investigate the integrated effect of variations in the atmosphere on the axial component of the Earth rotation vector, quantified as length of day (LOD) variations. Generally, larger emissions lead to some stronger zonal wind patterns in much of the upper atmosphere.  The long-term variability and trends in LOD are examined w.r.t. a multi-model-mean and compared with the respective variations in the projected global temperature to study the potential impact of global warming on the Earth rotation speed.
Observing seismic signatures of slow slip events with unsupervised learning
Authors: Seydoux Leonard , Campillo Michel , Steinmann René , Balestriero Randall , de Hoop Maarten
Published: March 2021

Slow slip events are observed in geodetic data, and are occasionally associated with seismic signatures such as slow earthquakes (low-frequency earthquakes, tectonic tremors). In particular, it was shown that swarms of slow earthquake can correlate with slow slip events occurrence, and allowed to reveal the intermittent behavior of several slow slip events. This observation was possible thanks to detailed analysis of slow earthquakes catalogs and continuous geodetic data, but in every case, was limited to particular classes of seismic signatures. In the present study, we propose to infer the classes of seismic signals that best correlate with the observed geodetic data, including the slow slip event. We use a scattering network (a neural network with wavelet filters) in order to find meaningful signal features, and apply a hierarchical clustering algorithm in order to infer classes of seismic signal. We then apply a regression algorithm in order to predict the geodetic data, including slow slip events, from the occurrence of inferred seismic classes. This allow to (1) identify seismic signatures associated with the slow slip events as well as (2) infer the the contribution of each classes to the overall displacement observed in the geodetic data. We illustrate our strategy by revisiting the slow-slip event of 2006 that occurred beneath Guerrero, Mexico.
Planning a geostatistical survey for mapping soil micronutrients: eliciting sampling densities
Authors: Milne Alice , Chagumaira Christopher , Lark Murray
Published: March 2021

When planning a geochemical survey, it is necessary to make decisions about the sampling density. Sampling density determines both the quality of predictions and the cost of field work. In geostatistical surveys, the relationship between sampling density and map quality, as measured by the kriging variance (mean square error of the prediction) can be computed. When the variogram is known, then the kriging variance at an unsampled site depends only on the spatial distribution of sampling points around that site. It is therefore possible to find the sample density such that the kriging variance is limited to acceptable values. However, the implications of kriging variances are not always straightforward for decision makers or sponsors of survey to understand. Here we present an alternative method to help end-users assess the implications of uncertainty in spatial prediction in so far as this is controlled by sampling.  It is called the offset correlation and is a measure of how far the mapped spatial variation depends on the positioning of a reqular square sampling grid.  The offset correlation increases as the uncertainty in the map, attributable to sample density, decreases.  It is bounded on the interval [0,1], which makes it intuitively easy to interpret as an uncertainty measure.  In this presentation we shall explain the offset correlation concept, illustrate it with some test cases, and provide session participants with an opportunity to join an elicitation of sampling density for a hypothetical survey of soil micronutrient status.

The offset correlation is an intuitive measure of the precision of a geostatistical mapping process because people can more easily grasp bounded measures like a correlation than unbounded ones like a variance.
Barrovian-type metamorphism in the western domain of the Cordillera Darwin Metamorphic Complex, Fuegian Andes
Authors: Calderon Mauricio , Zúñiga Catalina , Hervé Francisco , Theye Thomas , Galaz Gonzalo , Rojo Diego , Suárez Rodrigo
Published: March 2021

The Cordillera de Darwin Metamorphic Complex (CDMC) comprise metamorphosed supracrustal rocks and metaplutonic suites which records a unique tectonic evolution among the metamorphic complexes of the southernmost Andes. The pressure (P) and temperature (T) conditions determined in garnet-bearing schists in the Central Domain of the CDMC indicate a clockwise P-T path of metamorphism reaching burial depth as high as 12 kbar at ca. 620°C. This metamorphic event has been related to the closure of a marginal back-arc basin (Rocas Verdes Basin) and collision of an ensialic magmatic arc with the continent in the late Cretaceous. We focus on garnet-biotite schists intercalated within a huge block consisting of repeated sequences of metabasalts and amphibolites (Rocas Verdes Ophiolites), located in the Western Domain of the CDMC, at Seno Martínez. The chemical zonation of small garnet porphyroblasts (diameter of ca. 300 um) record two stages of metamorphism. Garnet is almost almandine in composition with lesser amounts of Ca, Mn and Mg.  The concentric zonation is characterized by relatively lower contents of Fe-Mg and higher contents of Ca-Mn in the core. Garnet bear tiny inclusions of clinozoisite, which is also present as isolated grains in the foliated matrix. Laths of biotite define the main foliation and have a nearly constant composition characterized by XFe of ca. 0.6. Two generations of phengitic white mica are identified on basis of Si content (a.pf.u.) varying between 3.20-3.30 (early generation) and of ca. 3.15 (late generation). To reconstruct the P-T conditions of metamorphism through thermodynamic modeling using the Perple_X software package, the bulk rock and mineral composition were considered. Using compositional isopleths of XFe, XMg, XCa and XMn in zoned garnet, Si content in white mica and XFe in biotite allow the constrain two stages of metamorphism (M1 and M2). The P-T conditions of M1, represented by the composition of the garnet core, are restricted to ca. 8 kbar and 400°C. M2 is restricted to ca. 7.5 kbar at 480°C, determined with the composition of the garnet rim, XFe in biotite and Si content in late phengitic white mica. Our preliminary results indicate that ophiolitic rocks and interleaved garnet-bearing schists were tectonically buried and metamorphosed in a relatively hot subduction interface characterized by a geothermal gradient of ca. 16°C/km, prior to the collision of the ensialic magmatic arc. Acknowledgements. This study was supported by the Fondecyt grant 1161818.
A data-driven stochastic parametrisation of intermittent turbulence in the stably stratified atmospheric boundary layer
Authors: Boyko Vyacheslav , Krumscheid Sebastian , Vercauteren Nikki
Published: March 2021

We present results on the modelling of intermittent turbulence in the nocturnal boundary layer using a data-driven approach. In conditions of high stratification and weak wind, the bulk shear can be too weak to sustain continuous turbulence, and the sporadic submeso motions play an important role for the turbulence production. We show a way to stochastically parametrise the effect of the unresolved submeso scales and include it into a 1.5-order turbulence closure scheme. This is achieved by introducing a stochastic equation, which describes the evolution of the non-dimensional flux-gradient stability correction for momentum ($\phi_m$). The unperturbed equilibrium solution of the equation follows the functional form of the universal similarity function. The stochastic perturbations reflect the instantaneous excursions from its equilibrium state, and the distribution of values covers the scatter found in observations at high stability.

The non-stationary parameters of this equations are estimated from a time-series data of the FLOSS2 experiment using a model-based clustering approach. The clustering analysis of the parameters shows a scaling relationship with the local gradient Ri number, leading to a suggested closed-form model for the stochastic flux-gradient stability correction. The spatial correlation in height of the perturbations is included in the model as well. The resulting equation captures the transition of the stability correction across and beyond the critical Ri up to a value of 10. The out-of-sample prediction shows a valid transient dynamics into and within the regime of strongly-stable stratification.
The burned area extracting in Chernobyl Exclusion Zone using Random Forest
Authors: Hu Jun , Kotsuki Shunji , Igarashi Yasunori , Talerko Mykola , Ichii Kazuhito
Published: March 2021

The Chernobyl Nuclear Power Plant (CNPP) accident that happened in 1986 is the largest source of anthropogenic radionuclides released into the environment in history. In recent 20 years, the climate and land-use changes have increased the frequency of large forest fires in and around the Chernobyl Exclusion Zone. It is critical to extract the burned areas accurately because they are the basis to estimate the biomass burning emission and then analyze the second diffusion of radioactive residue released from the CNPP accident. In this study, we established a burned area extracting method based on the random forest (RF) algorithm using the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD09GA / MYD09GA and LANDSAT -7 ETM+ /-8 OLI images. The field observation in 2015 and MODIS MOD14A1 (thermal anomaly data) product were adopted to generate sampling points for RF. The reflectance difference spectroscopy of near-infrared band and difference in vegetation indices (NDVI, NBR, NDWI) between pre- and post-fire imagery were used as input data for the RF classifier. Subsequently, the historical burned area in 2015 and 2020 were detected using the trained RF classifier. The preliminary results of the identified burned area show good consistency with the MODIS MCD64A1.006 product of NASA and FireCCI51product of ESA. It should be noted that our RF algorithm can even detect the relatively small fire scars compared to the two existing products due to the usage of high-resolution LANDSAT image.

 
Mapped-PCMCI: an algorithm for causal discovery at the grid level
Authors: Tibau Alberdi Xavier-Andoni , Gerhardus Andreas , Eyring Veronika , Denzler Joachim , Runge Jakob
Published: March 2021

We propose a novel causal discovery method for large-scale gridded time series datasets. Causal discovery has been applied to study a number of problems in climate research in recent years. Causal discovery can be conducted either among spatially aggregated variables (such as modes of climate variability) or by inferring a climate network where the associations among pairs of grid points are treated as a network. In the latter case, causal methods have to deal with several challenges arising from the high dimensionality of such datasets and the data's spatially and temporally redundant nature.

Our method, called Mapped-PCMCI, aims to overcome some of these challenges. The central idea is based on the assumption that there is a lower-dimensional representation of the causal dependencies among different locations. The method first reconstructs a lower-dimensional spatial representation of the data, then conducts causal discovery utilizing the PCMCI method (Runge. et al. 2019), in that lower-dimensional space, and finally maps causal relations back to the grid level. Using spatiotemporal data generated with the spatially aggregated vector-autoregressive (SAVAR) model (Tibau et al. 2020), we demonstrate that Mapped-PCMCI outperforms state-of-the-art methods in orders of magnitude by utilizing the assumption of a lower-dimensional dependency structure. Mapped-PCMCI can be used to better estimate climate networks and thereby help to understand the climate system from the perspective of complex network theory.

 

J. Runge, P. Nowack, M. Kretschmer, S. Flaxman, D. Sejdinovic, Detecting and quantifying causal associations in large nonlinear time series datasets. Sci. Adv. 5, eaau4996 (2019).

Tibau, X.-A., Reimers, C., Eyring, V., Denzler, J., Reichstein, M., and Runge, J.: Spatiotemporal model for benchmarking causal discovery algorithms, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9604, https://doi.org/10.5194/egusphere-egu2020-9604, 2020
Propagation properties of foreshock cavitons and spontaneous hot flow anomalies: Statistical results from a global hybrid-Vlasov simulation
Authors: Tarvus Vertti , Turc Lucile , Battarbee Markus , Suni Jonas , Blanco-Cano Xóchitl , Ganse Urs , Pfau-Kempf Yann , Alho Markku , Dubart Maxime , Grandin Maxime , Johlander Andreas , Papadakis Konstantinos , Palmroth Minna
Published: March 2021

Foreshock cavitons are transient structures forming in Earth's foreshock as a result of non-linear interaction of ultra-low frequency waves. Cavitons are characterised by simultaneous density and magnetic field depressions with sizes of the order of 1 Earth radius. These transients are advected by the solar wind towards the bow shock, where they may accumulate shock-reflected suprathermal ions and become spontaneous hot flow anomalies (SHFAs), which are characterised by an enhanced temperature and a perturbed bulk flow inside them.
    Both spacecraft measurements and hybrid simulations have shown that while cavitons and SHFAs are carried towards the bow shock by the solar wind, their motion in the solar wind rest frame is directed upstream. In this work, we have made a statistical analysis of the propagation properties of cavitons and SHFAs using Vlasiator, a hybrid-Vlasov simulation model. In agreement with previous studies, we find the transients propagating upstream in the solar wind rest frame. Our results show that the solar wind rest frame motion of cavitons is aligned with the direction of the interplanetary magnetic field, while the motion of SHFAs deviates from this direction. We find that SHFAs have a faster solar wind rest frame propagation speed than cavitons, which is due to an increase in the sound speed near the bow shock, affecting the speed of the waves in the foreshock.
Strength and Challenges of global model MPAS with regional mesh refinement for mid-latitude storm forecasting: A case study
Authors: Imberger Marc , Larsén Xiaoli Guo , Davis Neil
Published: March 2021

Mid-latitude storms are large-scale weather patterns. They involve a large range of spatial and temporal atmospheric scales of motion. Their characteristic extreme precipitation, wind gusts and high surface winds can significantly impact wind farms (e.g. shutdowns of turbines due to exceedance of cut-off wind speed) affecting grid performance and safety. Adequate storm forecasting, which relies on high spatial model resolution, is crucial. Traditional methods usually involve the use of limited area models (LAMs). While the performance of LAMs is generally satisfactory, challenges arise when large-scale storm structures enter near the the lateral boundaries of the LAM. In this case, insufficient update intervals of the forcing data at the lateral boundaries and spatial and temporal interpolation can deteriorate the storm structure that cause insufficient storm deepening. The global Model for Prediction Across Scales (MPAS) with regional mesh refinement avoids lateral boundary conditions and allows refinement with smooth transition zones. Based on a case study of storm “Christian”, MPAS’ capabilities in simulating key storm characteristics are explored in this work. Buoy measurements of sea level pressure, reanalysis and forecast products from the Climate Forecast System (CFSv2) and simulations with the Weather Research and Forecasting (WRF) model are used to evaluate the forecast performance with respect to storm intensity, storm arrival time and storm duration. A mesh configuration with refinement from 54-km to 18-km (further referred to as variable-resolution mesh) is compared with quasi-uniform mesh configurations to examine the impact of transition zone and mesh refinement on the storm structure and forecast performance. It is found that MPAS is generally able to predict the storm intensity based on the local minimum sea level pressure, while the estimation of storm arrival time and storm duration have been negatively influenced by model drifts in MPAS and by impacts of the transition zone on the storm development in the variable-resolution configuration. An additional low pressure system emerged in the variable-resolution mesh whereby its presence is sensitive to model physics. The investigation highlights the importance of the transition zone design in MPAS and the need for additional strategies like data assimilation techniques to prevent model drifts for storm forecasting.
Drivers of carbon dioxide fluxes in high-Arctic tundra: data-driven models
Authors: Magnani Marta , Baneschi Ilaria , Gaimberini Mariasilvia , Provenzale Antonello
Published: March 2021

Arctic regions are extreme environments where ecosystems are undergoing significant changes induced by the temperature rise, that is progressing about twice faster than in the rest of the world. In the high-Arctic, the Critical Zone (CZ) has a thin above-ground component, consisting of tundra vegetation, and a highly seasonal below-ground component, with varying extension and chemical-physical characteristics. The complexity of this system makes future projections of the Arctic CZ a challenging goal. In particular, it is still unclear whether the system will turn from a carbon sink to a carbon source. On the one hand, the uptake of carbon dioxide (CO2) by vegetation is expected to increase in future years owing to the widening growing season and the shift in community composition but, on the other, increasing soil temperatures are fostering carbon release by thawing permafrost and degradation of organic matter through heterotrophic respiration in deglaciated soils. In this work, we identified the main biotic and abiotic drivers of CO2 emissions (Ecosystem Respiration, ER), and CO2 uptake (Gross Primary Production, GPP), in the Arctic tundra biome. During summer 2019 we extensively measured CO2 fluxes at the soil-vegetation-atmosphere interface, basic meteoclimatic variables and ecological descriptors at the Critical Zone Observatory of Bayelva river basin (CZO@Bayelva), Spitzbergen, in the Svalbard Archipelago (NO). Flux measurements were obtained by a portable accumulation chamber, allowing for the statistical analysis of fluxes variability at small scale. Together with flux measurements, we sampled soil temperature and humidity at the chamber base and local air temperature, pressure and humidity. In addition, the vegetation cover was obtained from digital RGB pictures of the sampled surfaces. By means of multi regression models, we related flux data to environmental parameters, vegetation cover extent and vegetation type, thus obtaining empirical data-driven models that describe the coupled dynamics of soil, vegetation, water and atmosphere that contribute to the present budgeting of the carbon cycle in the arctic CZ. This work may help in assessing the possible future evolution of high-Arctic environment under projected changes in vegetation community composition and abiotic parameters.
Interplanetary Shock-driven Magnetopause Compressions in Gorgon Global-MHD Simulations
Authors: Desai Ravindra , Eastwood Jonathan , Eggington Joseph , Freeman Mervyn , Archer Martin , Shprits Yuri , Meredith Nigel , Hietala Heli , Mejnertsen Lars , Chittenden Jeremy , Horne Richard
Published: March 2021

Fast-forward interplanetary interplanetary shocks, as occur at the forefront of interplanetary coronal mass ejections and at corotating interaction regions, can rapidly compress the magnetopause inside the drift paths of electrons and protons, and expose geosynchonous satellites directly to the solar wind.  Here, we use Gorgon Global-MHD simulations to study the response of the magnetopause to different fast-forward interplanetary shocks, with strengths extending from the median shocks observed during solar minimum up to that representing an extreme space weather event. The subsequent magnetopause response can be characterised by three distinct phases; an initial acceleration as inertial forces are overcome, a rapid compression well-represented by a power law, and large-scale damped oscillatory motion of the order of an Earth radius, prior to reaching pressure-balance equilibrium. The subsolar magnetopause is found to oscillate with notable frequencies in the range of 2–13 mHz over several periods of diminishing amplitudes.  These results provide an explanation for similar large-scale magnetopause oscillations observed previously during the extreme events of August 1972 and March 1991 and highlight why static magnetopause models break down during periods of strong solar wind driving.
“Young Innovators” story: case study of Latvia
Authors: Kalvane Gunta , Krastiņa Santa
Published: March 2021

STEM teachers in Latvia acknowledge that the climate issue is one of the most difficult and incomprehensible topics for students because of the complexity of the climate system itself and because that students do not see the consequences and responsibilities of their actions. In addition, there is little climate-related teaching materials available in Latvian language.

In 2020, we have implemented the experience of EIT Climate-KIC project “Young Innovators” into the school's curriculum and nonformal education (through Latvian 4Hclub – leading and largest NGO) in Latvia.

“Young Innovators” is a pilot program for youngsters (12-18), to promote their entrepreneurial and social skills, systemic thinking aimed at tackling climate change, reducing environmental problems and improving the living environment. Together with stakeholders they are working on real-life challenges (more about the program: https://younginnovators.climate-kic.org/about-the-programme/).

We started with the webinar cycle for NGO leaders in April (it should be noted, that for many of them it was their first webinar ever), while in August the webinars were organized for geography and STEM teachers. In the summer (when restrictions were lifted) we had workshops with students: using the mind map and photo-voting methods, we identified the most important areas for students and the major environmental problems. Using the project tools, the analytical assessment and visioning of the problem has been done. The last step was – visiting the local authorities.

In addition, at the end of August we organized a 3-hour Climathon (total 250 participants), where we worked on the challenges given by the stakeholder - WWF (Waste food), Enefit Latvija (green energy solutions); national fruit growers (local apples marketing campaigns) etc.

Project methods and tools can be used in both – formal and non-formal education systems and were welcomed by both students and teachers.

Activities were carried out within the framework of EIT Climate-KIC financial support.
A decreasing trend in global soil water storage from 1981 to 2017
Authors: Luo XinRui , Li Shaoda , Yang Wunian , Liu Liang , Tang Xiaolu
Published: March 2021

Soil water storage serves as a vital resource of the terrestrial ecosystems, and it can significantly influence water cycle and carbon cycling with the frequent occurrence of soil drought induced by land-atmosphere feedbacks. However, there are high variations and uncertainties of root zone soil water storage. This study applied comparison map profile (CMP), Mann-Kendall test, Theil-Sen estimate and partial correlation analysis to (1) estimate the global root zone (0~1 m) soil water storage, (2) and investigate the spatial and temporal patterns from 1981 to 2017 at the global scale, (3) and their relationships with environmental drivers (precipitation, temperature, potential evaportranspiration) using three soil moisture (SM) products – ERA-5, GLDAS and MERRA-2. Globally, the average annual soil water storage from 1981 to 2017 varied significantly, ranging from 138.3 (100 Pg a-1, 1 Pg = 1015 g) in GLDAS to 342.6 (100 Pg a-1) in ERA-5. Soil water storage of the three SM products consistently showed a decreasing trend. However, the temporal trend of soil water storage among different climate zones was different, showing a decreasing trend in tropical, temperate and cold zones, but an increasing trend in polar regions. On the other hand, temporal trends in arid regions differed from ERA-5, GLDAS and MERRA-2. Spatially, the SM products differed greatly, particularly for boreal areas with D value higher for 2500 Mg ha-1 a-1 and CC value lower for -0.2 between GLDAS and MERRA-2. Over 1981 to 2017, water storage of more than 50% of the global land area suffered from a decreasing trend, especially in Africa and Northeastern of China. Precipitation was the main dominated driver for variation of soil water storage, and distribution varied in different SM products. In conclusion, a global decreasing trend in soil water storage indicate a water loss from soils, and how the water loss affecting carbon sink in terrestrial ecosystems under ongoing climate change needs further investigation.