bluuebunny/crossref_metadata_2025 huggingface dataset:
Porosity estimation and characterization of a geothermal carbonate reservoir in the South German Molasse Basin based on seismic inversion and attribute analysis
Authors: Wadas Sonja , von Hartmann Hartwig
Published: March 2021

The Molasse Basin is one of the most promising areas for deep geothermal exploration in Germany and a very ambitious project in this region is to power the entire district heating system of the city of Munich with renewable energies by 2040; a major part of this will consist of geothermal energy. As part of a joint project (financed by the German Federal Ministry For Economic Affairs And Energy; FKZ 0324332B) the Leibniz Institute for Applied Geophysics (LIAG) works together with the Munich City Utilities (Stadtwerke München), to improve reservoir characterization and sustainable reservoir exploration within the German Molasse Basin. The target horizon for hydrothermal exploration is the aquifer in the Upper Jurassic carbonates. A major problem is the strong heterogeneity of the carbonates. Compared to quantity and quality of the structural data of the reservoir, the database of reservoir properties such as density, porosity and permeability, which describe the geothermal potential, is insufficient. Therefore, it is necessary to generate such data in order to improve the value of the structural information. A 3D seismic survey cannot only provide structural information, but also important reservoir properties such as elastic parameters and seismic attributes. One of the most important attributes is the acoustic impedance, which can be determined with a seismic inversion and used to estimate a porosity volume.

The data basis for this study was the 170km² GRAME-3D seismic survey measured in Munich, a structural geological model, and drilling and logging data from the geothermal site “Schäftlarnstraße”.

The inversion results show low impedance values at the top of the reservoir, but also at the middle part. Spatially, the intermediate block of the Munich fault shows low values but also the eastern part of the hanging wall block and the western part of the footwall block. Based on a well correlation a relationship between acoustic impedance and porosity could be determined and a 3D porosity volume was calculated. In the upper part but also in the middle part of the reservoir areas with increased porosity (>10%) are shown, which might indicate a high geothermal potential.

For a better classification, an attribute analysis was performed. The intermediate block and the eastern part of the hanging wall block show strongly fractured rocks. In contrast, there are hardly any conspicuous features in the western part of the footwall block, although high porosities are also expected here. This suggests that the presence of faults is not the only factor favoring high porosities in carbonates. More likely is a combination with karstification processes, which is why even areas that do not show enhanced tectonic deformation have high porosities.
Towards a conditional representation of heat wave probability in large ensemble climate model data
Authors: Zeder Joel , Fischer Erich M.
Published: March 2021

Research Objective: Single-model initial condition large ensembles provide novel opportunities to study the physical drivers and risks of large-scale climate extremes in a changing climate. The probability of extremes such as weekly heatwaves, here quantified as seven-day maximum temperature (Tx7d), are usually approximated with a general extreme value distribution GEV  that is stationary or accounts for non-stationarity of a warming climate. However, estimating the occurrence probability of very rare climate extremes in the presence of large internal variability further benefits from the integration of process-based covariates characterising the preceding and concurrent climate conditions both at global and local scale.

Data & Methods: We here use more than 6000 years of stationary pre-industrial and 2xCO2 control simulations and an ensemble of 84 transient historical and RCP8.5 simulations performed with the Community Earth System Model CESM1.2 to develop and robustly test methods of quantifying extreme events under a broad range of climatic conditions. The generalised extreme value distribution is parametrised such that it can account for changing environmental circumstances, ranging from large-scale thermodynamic non-stationarity due to climate change, regional-scale dynamic forcing such as atmospheric blocking, or local land-surface conditions such as soil moisture deficits. Fields of covariates are integrated using approaches from statistical learning theory, accounting for the spatio-temporal correlation inherent in climate data.

Preliminary results: Dynamical forcing patterns as simulated by the earth system model compare well with those obtained from reanalysis data and inform the statistical model in a physically traceable fashion. How well the latter generalises is tested with respect to further simulations of the US CLIVAR Working Group on Large Ensembles. The relevance of different covariates can inform both detection and attribution as well as risk assessment how their respective statistical models can be further refined to account for the influence of physical drivers under present and future climate conditions.
Dependence of Indian summer monsoon rainfall forecast skill of CFSv2 on initial conditions and the role of bias in SST boundary forcing
Authors: Varghese Stella Jes , Rajendran Kavirajan , Surendran Sajani , Chakraborty Arindam
Published: March 2021

Indian summer monsoon seasonal reforecasts by CFSv2, initiated from January (4-month lead time, L4) through May (0-month lead time, L0) initial conditions (ICs), are analysed to investigate causes for the highest Indian summer monsoon rainfall (ISMR) forecast skill of CFSv2 with February (3-month lead time, L3) ICs. Although theory suggests forecast skill should degrade with increase in lead-time, CFSv2 shows highest skill with L3, due to its forecasting of ISMR excess of 1983 which other ICs failed to forecast. In contrast to observation, in CFSv2, ISMR extremes are largely decided by sea surface temperature (SST) variation over central Pacific (NINO3.4) associated with El Niño-Southern Oscillation (ENSO), where ISMR excess (deficit) is associated with La Niña (El Niño) or cooling (warming) over NINO3.4. In 1983, CFSv2 with L3 ICs forecasted strong La Niña during summer, which resulted in 1983 ISMR excess. In contrast, in observation, near normal SSTs prevailed over NINO3.4 and ISMR excess was due to variation of convection over equatorial Indian Ocean, which CFSv2 fails to capture with all ICs. CFSv2 reforecasts with late-April/early-May ICs are found to have highest deterministic ISMR forecast skill, if 1983 is excluded and Indian monsoon seasonal biases are also reduced. During the transitional ENSO in Boreal summer of 1983, faster and intense cooling of NINO3.4 SSTs in L3, could be due to larger dynamical drift with longer lead time of forecasting, compared to L0. Boreal summer ENSO forecast skill is also found to be lowest for L3 which gradually decreases from June to September. Rainfall occurrence with strong cold bias over NINO3.4, is because of the existence of stronger ocean-atmosphere coupling in CFSv2, but with a shift of the SST-rainfall relationship pattern to slightly colder SSTs than the observed. Our analysis suggests the need for a systematic approach to minimize bias in SST boundary forcing in CFSv2, to achieve improved ISMR forecasts.
UAV high-resolution magnetic mapping of the Chenaillet ophiolite, in the Alps
Authors: Le Maire Pauline , Thieblemont Denis , Munschy Marc , Martelet Guillaume , Mohn Geoffroy
Published: March 2021

Continent-Ocean Transitions (COT) and ultra-slow spreading ridges, floored by wide area of exhumed serpentinized mantle, bear strong amplitude magnetic lineations. However, whether these anomalies are linked to inversions of the direction of the magnetization (therefore characterized as isochrones of seafloor spreading) or to structural and lithological contrasts remains an open question. Generally, marine magnetic data acquired at sea surface along profiles, are too low resolution to image the intensity variations of the magnetic field at a kilometric scale. Performing a dense deep tow magnetic survey at a present-day COT or ultra-slow spreading system would be better to determine the sources of the magnetic signal but remains expensive. To go ahead, a valuable alternative to address these questions is to record the magnetic signal on ophiolite representing remnants of COT and oceanic systems sampled in orogenic system. We worked on the Chenaillet Ophiolite (French Alps), which represents a fossil COT or ultra-slow spreading system integrated to the Alpine orogeny. This ophiolite escaped high-pressure metamorphism and has only been weakly deformed during Alpine orogeny, preserving its pre-orogenic structure.

We performed an UAV magnetic survey using fluxgate magnetometers in complex conditions due to the altitude (> 1800 m), the strong topography variations and the weather conditions (negative temperatures, snow). Despite these difficulties, which highlight the viability of UAV for geophysical measurements, a survey of 20 square kilometers with 219 km of profiling was completed 100 m above ground level. Flight line spacing is 100 m above the ophiolitic basement and 200 m above the sedimentary units. Another magnetic UAV survey was flown with another UAV to map a small area 10 m above ground level. Magnetic anomaly maps were computed after standard processing (e.g., calibration/compensation, temporal variation and regional magnetic field corrections, levelling).

Our first results evidence well-defined magnetic anomalies clearly linked to serpentinite. This shows that the magnetic signal is of sufficient resolution to contribute to a revision of the cartography of the massif combining geological observations and magnetic data.

In addition, the magnetic susceptibility was measured on 60 outcrops, to support interpretation.

In this presentation, we focus on the magnetic acquisition campaigns, processing and 2D/3D interpretations by forward modelling and data inversion. Lastly, two items are discussed: 1) contribution of magnetic UAV surveys for geological mapping; and 2) implication of the results on the Chenaillet massif to discuss the contribution of magnetic mapping to the understanding of the TOC or ultra-slow spreading system.
Surface Radiation Characteristics of the Ali Area, Northern Tibetan Plateau
Authors: Wang Ge , Han Lin
Published: March 2021

This study analyses the diurnal seasonal mean and the seasonal and annual variation in the radiation budget at the Ali Meteorological Bureau observation station in the northern Tibetan Plateau for 2019. The results indicate that the daily average variation in incidental shortwave and reflected radiation across all seasons in the Ali area had typical unimodal symmetry. The average daily variation in incidental shortwave radiation was in phase with reflected radiation, but the amplitude of the incidental shortwave radiation was greater than that of reflected radiation. The daily amplitude, daily average, and monthly average upwelling longwave radiation were greater than those for downwelling radiation, and the diurnal cycle of downwelling atmospheric radiation lagged behind that of upwelling longwave radiation. The daily amplitude of surface net radiation in winter in the Ali area was less than in other seasons, as expected, and the seasonal transformation had a great impact on the net radiation for this region. The net radiative energy at the surface was highest in late spring and early summer, which played a decisive role in the formation of terrestrial and atmospheric heating.
Promote Nature-Based Solutions to adapt the environment to climate change – The LIFE ARTISAN project
Authors: Versini Pierre-Antoine , Schertzer Daniel , Loury Mathilde
Published: March 2021

Nature-Based Solutions (NBS) appear as some relevant alternatives to mitigate the consequences of climate change. For this reason, they are promoted for the implementation of the national plan for adaptation to climate change (PNACC) in France, in line with the Paris Agreement, the strategy of the European Union for adaptation to climate change and the French national strategy for biodiversity.

Nevertheless, this ambitious goal of democratizing NBS poses some institutional and technical challenges because many obstacles remain to their implementation. Overcoming these shortcomings is the objective of the LIFE integrated project called ARTISAN (Achieving Resiliency by Triggering Implementation of nature-based Solutions for climate Adaptation at a National scale). Coordinated by the French Biodiversity Office (OFB), its consortium regroups several local authorities, technical, research and education institutes.

For this purpose, ARTISAN is creating a framework promoting the implementation of NBS by improving scientific and technical knowledge about them, then by developing and disseminating relevant tools for project leaders (for the design, sizing, implementation and evaluation of ecosystem performance).

To demonstrate that NBS can respond to a diversity of climatic, ecological and institutional contexts, 10 pilot sites will be monitored in metropolitan and overseas France. The concerned issues are for example the reduction of urban heat island by the de-waterproofing of the public space, the limitation of the impact of cyclonic episodes on the urbanized coastline overseas by promoting the restoration of the mangrove, and the decrease of agricultural water stress during the low flow period by the hydromorphological restoration of wetlands. These pilot sites will serve to develop, improve and validate operational tools, methods and trainings devoted to practitioners.
Recurrence of megathrust events: Impact on hazard and risk in South America
Authors: Woessner Jochen , Velasquez Jessica , Nyst Marleen , Fitzenz Delphine , Eads Laura
Published: March 2021

Megathrust earthquakes along the South American subduction zone where the Nazca plate slips below the South American plate rapidly subducts below the South American plate contribute significantly to the seismic hazard in Chile, Peru, Ecuador and Colombia. Estimating recurrence of the megathrust events is of prime interest not only for securing effective counter measures for engineering purposes, but also for assessing seismic hazard and risk for appropriate disaster risk management solutions in the insurance sector.

We present an evaluation and interpretation of recent research on the recurrence of megathrust earthquakes along the South America subduction zone. The modelling approach is conceptually founded in the asperity model and in this spirit evidence for documented earthquakes is assembled. We utilize time-independent and time-dependent recurrence models to understand the range and likelihood of recurrence times given the incomplete picture of the seismic history and the impact from uncertain event dates based on paleo-seismic / paleo-tsunami studies. In addition, we illustrate the sensitivity of recurrence rates for the largest earthquakes due to assumptions on seismic coupling and the size of potential ruptures.

Downstream from the recurrence rate analysis, the results are used to estimate the impact of the subduction interface model seismicity on a select set of exposure subject to earthquake shaking due to those events. These examples highlight the potential range of seismic hazard and risk and set the basis to further constrain disaster risk management solutions. 
Reconstructing post-earthquake sediment cascades in mountain landscapes from the sedimentary record
Authors: Howarth Jamie , Fitzsimons Sean , Hilton Robert , Moody Adelaine , Croissant Thomas , Wang Jin , Densmore Alex , McClymont Erin
Published: March 2021

Strong ground motions from major earthquakes trigger tens of thousands of landslides in mountain landscapes initiating a sediment cascade that ultimately elevates sediment and carbon fluxes in rivers. The magnitude and duration of the fluvial response to earthquake-induced landsliding is relevant for quantifying post-earthquake hazard, landscape evolution and carbon cycling but remains poorly constrained in many mountain settings because post-earthquake sediment cascades are rarely captured by instrumental data series. The sedimentary record may provide a valuable archive of the landscape response to earthquakes in the absence of instrumental data but requires the signature of post-earthquake sediment cascades to be reliably identified and quantified. Here we use sedimentary archives of lakes adjacent to the Southern Alps, New Zealand to reconstruct earthquake-induced erosion in response to great earthquakes on the range bounding Alpine Fault; the timing, location and magnitude of which have been well constrained by independent paleoseismic data. High-resolution chronology combined with volumetric reconstructions of lacustrine sedimentary fills based on a dense network of sediment cores from two lakes fed by range front catchments allow sediment and carbon fluxes to be quantified over millennial timescales. The volumetric reconstructions show earthquake-induced landsliding increased suspended sediment and organic carbon (OC) transfers from the mountain belt by more than an order of magnitude immediately after each earthquake. While elevated fluxes persisted for decades, the majority of sediment and OC was exported within the first five to ten years after each large earthquake. In total, the last four Mw>8 earthquakes on the Alpine Fault have driven sediment and OCtransfers that equate to ~40% of the total flux over the last millennium. Further, biomarkers encoded in the OC allow the location and depth of earthquake-triggered landslides to be reconstructed. The Southern Alps case study demonstrates that post-earthquake sediment cascades in mountain catchments are reliably recorded in the sedimentary record. These records provide unprecedented insights into post-earthquake hazard in settings where major earthquakes have not occurred during the period of instrumental observation.
Evaluation of 2 years seismic monitoring for geothermal development in Vienna, Austria 
Authors: Apoloner Maria-Theresia , Rodler Fee-Alexandra , Lenhardt Wolfgang
Published: March 2021

Possible geothermal water resources in the eastern part of Vienna could ideally provide hundreds of thousands of Viennese households with environmentally friendly heat and hot water. Currently, the potential of low-lying hot water resources in this area is being explored geologically and geophysically within the scope of the multi-disciplinary project GeoTief Explore 3D.

For the development of geothermal projects, studies of historical seismicity and monitoring of current seismicity are basic requirements. Therefore, we deployed a seismic network consisting of four stations in the area of interest in 2019. After 2 years of recording, we search the data for previously undetected small magnitude local earthquakes. Also we evaluate the local background noise and its variability with time. Based on these results, we estimate site-specific detection thresholds within in the project area.
Capacity of Quercus robur L. and Tilia cordata Mill. trees in providing urban ecosystem services in boreal climate
Authors: Sushko Sofia , Yaroslavtsev Alexey , Tsuvareva Nina , Valentini Riccardo
Published: March 2021

Trees play an important role in urban ecosystem functioning and providing many ecosystem services, in particular, water and energy balance regulation. Consequently, trees can be a tool to mitigate to run-off and heat island effect in urban areas. We quantified the possibility of urban trees to provide these ecosystem services in the northernmost city with a million population – St. Petersburg (59°57′ N / 30°19′ E; Russia). Two diffuse-porous tree species – Quercus robur L. (n=2) and Tilia cordata Mill. (n=4) – were chosen for the research. These tree species are the most common in the green infrastructure of the city despite they are not typical for this biome, i.e. south taiga. During two growing season (July-Oct. 2019, April-Oct. 2020), tree sap flux was measured by thermal dissipation method using TreeTalker device (Nature 4.0 Corp., Italy). Sap flux density (Js) was calculated with modified Granier’s empirical calibration equation. Energy loss through tree transpiration was estimated from sap flux per tree (Js × sap wood area) and latent heat of vaporization. For the entire observed period, average daily Js (24 h) of Q. robur trees were almost two times higher than T. cordata trees (3.46 vs. 1.91 g cm-2 h-1). Importantly, for Q. robur Js significantly decreased with increasing tree age (from 3.75 to 1.99 g cm-2 h-1 with age alteration from 145 to 350 yrs.), while for T. cordata it did not change (1.74 and 1.69 g cm-2 h-1 for 60-80 and 100-115 yrs.). Q. robur showed a significant higher daily energy loss through tree transpiration compared to T. cordata (618 and 396 W tree-1 with 100-108 diameter at breast high) for the studying period. Thus, Q. robur compared to T. cordata was more effective in providing water regulation services, especially in shallow groundwater table typical for St. Petersburg. Moreover, this tree species also has a higher capacity in mitigate to urban heat island effect.

Current research was financially supported by Russian Science Foundation, No 19-77-30012.
Land Water Storage Variabilities in GRACE and Climate Models – How do they compare and which future changes can we expect?
Authors: Jensen Laura , Eicker Annette , Dobslaw Henryk , Pail Roland
Published: March 2021

Climate change will affect terrestrial water storage (TWS) during the next decades by impacting the seasonal cycle, interannual variations, and long-term linear trends. But how exactly will the variability change in the future? Reliable projections are needed not only for sensible water management but also as input for long-term performance studies of possible Next Generation Gravity Missions (NGGMs).

In this contribution, an ensemble of climate model projections provided by the Coupled Model Intercomparison Project Phase 6 (CMIP6) covering the years 2002 – 2100 is utilized to assess possible changes in TWS variability. To demonstrate performance and identify shortcomings of the models we first compare modeled TWS to globally observed TWS from the Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO) in the time span 2002 – 2020. We then analyze changes in the variability of TWS from model projections until the end of the century and the consensus on such changes within the model ensemble.

Based on these projections, we find that present-day GRACE accuracies are sufficient to detect amplitude and phase changes in the seasonal cycle in one third of the land surface after 30 years of observation, whereas a five times more accurate NGGM mission could resolve such changes almost everywhere outside the most arid landscapes of our planet. We also select one individual model experiment out of the CMIP6 ensemble that closely matches both GRACE observations and the multi-model median of all CMIP6 realizations. This model run might serve as basis for multi-decadal satellite mission performance studies to demonstrate the suitability of NGGM satellite missions to monitor long-term climate variations in the terrestrial water cycle.
Riverscape-scale airborne TIR assessment of weirs and riparian cover effects on lowland river temperature 
Authors: Marteau Baptiste , Chandesris André , Cernesson Flavie , Michel Kristell , Vaudor Lise , Piégay Hervé
Published: March 2021

The development of Airborne Infrared Thermal sensing (TIR) is an example of how technological advancements and the field that they focus on have fostered one another. The pace at which global change is occurring has fed the demand for better understanding of the thermal behaviour of rivers. In turn, the improvement of remote sensing and data processing techniques has provided researchers and managers with new tools to apprehend such aspects at ever larger scales. Still, recent studies have mostly focussed on rivers showing little human alteration, with a particular interest on groundwater–surface water interactions. Lowland streams are scarcely considered when it comes to the study of temperature despite their widespread occurrence, their relatively high degree of disturbance and the risks that they face in the light of temperature rising following climate change. Some of these streams already display critically high maximum summer temperatures and their state is likely to worsen in the future, putting all compartments of biota at risk.

The aims of this project were twofold. We first tested the applicability of airborne TIR to study lowland, slow-flowing stream reaches draining agricultural catchments, some of which being particularly narrow and sinuous. We then sought to understand the role of different environmental factors, observed in such context, on driving river temperature during the warmest days of the year. A number of anthropogenic actions such as clear-cutting of riparian trees, stream rectification and the construction of weirs are likely to influence the longitudinal temperature profile of such streams. By choosing rivers with no or limited groundwater inputs, we were able to quantify the relative role of each of the three tested factors and identify stream sections showing critically high maximum temperature over the summer.

A final step was proposed to upscale these results in order to identify sections of streams showing high risks of reaching critically high summer temperature at a regional network scale. To do so, we used a combination of high resolution land-cover data, digital elevation models and other existing databases (e.g. national inventory of weirs). Identification of the risks in relation with the relative contribution of the different factors is key to process-based river management. This type of output is valuable to river basin managers and decision makers as it can be used to implement targeted restoration initiatives or remediation actions in areas where these have higher chances of being effective.
Co-location of SLR and GNSS techniques onboard Galileo and GLONASS satellites
Authors: Bury Grzegorz , Sośnica Krzysztof , Zajdel Radosław , Strugarek Dariusz , Hugentobler Urs
Published: March 2021

All satellites of the Galileo and GLONASS navigation systems are equipped with laser retroreflector arrays for Satellite Laser Ranging (SLR). SLR observations to Global Navigation Satellite Systems (GNSS) provide the co-location of two space geodetic techniques onboard navigation satellites.

SLR observations, which are typically used for the validation of the microwave-GNSS orbits, can now contribute to the determination of the combined SLR+GNSS orbits of the navigation satellites. SLR measurements are especially helpful for periods when the elevation of the Sun above the orbital plane (β angle) is the highest. The quality of Galileo-IOV orbits calculated using combined SLR+GNSS observations improves from 36 to 30 mm for β> 60° as compared to the microwave-only solution. 

Co-location of two space techniques allows for the determination of the linkage between SLR and GNSS techniques in space. Based on the so-called space ties, it is possible to determine the 3D vector between the ground-based co-located SLR and GNSS stations and compare it with the local ties which are determined using the ground measurements. The agreement between local ties derived from co-location in space and ground measurements is at the level of 1 mm in terms of the long-term median values for the co-located station in Zimmerwald, Switzerland.

We also revise the approach for handling the SLR range biases which constitute one of the main error sources for the SLR measurements. The updated SLR range biases consider now the impact of not only of SLR-to-GNSS observations but also the SLR observations to LAGEOS and the microwave GNSS measurements. The updated SLR range biases improve the agreement between space ties and local ties from 34 mm to 23 mm for the co-located station in Wettzell, Germany.

Co-location of SLR and GNSS techniques onboard navigation satellites allows for the realization of the terrestrial reference frame in space, onboard Galileo and GLONASS satellites, independently from the ground measurements. It may also deliver independent information on the local tie values with full variance-covariance data for each day with common measurements or can contribute to the control of the ground measurements as long as both GNSS and SLR-to-GNSS observations are available.
A systematic assessment of water vapor products in the Arctic: from instantaneous measurements to monthly means
Authors: Crewell Susanne , Ebell Kerstin , Konjari Patrick , Mech Mario , Nomokonova Tatiana , Radovan Ana , Strack David , Triana-Gomez Aranxta , Noel Stefan , Scarlat Raul , Spreen Gunnar , Maturilli Marion , Annette Rinke , Irina Gorodetskaya , Viceto Carolina , August Thomas , Schröder Marc
Published: March 2021

Water vapor is an important component in the water and energy cycle of the Arctic. Especially in the light of Arctic amplification, changes of water vapor are of high interest but are difficult to observe due to the data sparsity of the region. The ACLOUD/PASCAL campaign performed in May/June 2017 in the Arctic North Atlantic sector offers the opportunity to investigate the quality of various satellite and numerical model reanalysis products. For this purpose reference Integrated Water Vapor (IWV) measurements at R/V Polarstern frozen into the ice (around 82° N, 10° E) and at t Ny-Ålesund are used to investigate the quality of instantaneous satellite retrievals from AIRS, AMSR2, GOME2, IASI and MIRS. These products use different parts of the electromagnetic spectrum and have different uncertainty characteristics related to the presence of clouds and/or surface characteristics. Therefore, the analysis is expanded to all radiosonde stations within the region. Due to the strong spatio-temporal variability of IWV - in particular during atmospheric river events - sampling issues are important that arise due to the different satellite orbits as well the synoptic radiosonde launch times. Following up on this analysis the question arises whether the satellite data are suitable for a long-term monitoring and trend assessment of water vapor in the Arctic. For this purpose we will also present an analysis of monthly mean values for May and June 2017 - two months with strongly changing surface characteristics in the Arctic - and investigate their performance relative to various reanalyses.
Using machine learning to downscale simulations of climate change induced changes to the shallow groundwater table
Authors: Schneider Raphael , Henriksen Hans Jørgen , Koch Julian , Troldborg Lars , Stisen Simon
Published: March 2021

The DK-model (https://vandmodel.dk/in-english) is a national water resource model, covering all of Denmark. Its core is a distributed, integrated surface-subsurface hydrological model in 500m horizontal resolution. With recent efforts, a version at a higher resolution of 100m was created. The higher resolution was, amongst others, desired by end-users and to better represent surface and surface-near phenomena such as the location of the uppermost groundwater table. Being presently located close to the surface across substantial parts of the country and partly expected to rise, the groundwater table and its future development due to climate change is of great interest. A rising groundwater table is associated with potential risks for infrastructure, agriculture and ecosystems. However, the 25-fold jump in resolution of the hydrological model also increases the computational effort. Hence, it was deemed unfeasible to run the 100m resolution hydrological model nation-wide with an ensemble of climate models to evaluate climate change impact. The full ensemble run could only be performed with the 500m version of the model. To still produce the desired outputs at 100m resolution, a downscaling method was applied as described in the following.

Five selected subcatchment models covering around 9% of Denmark were run with five selected climate models at 100m resolution (using less than 3% of the computational time for hydrological models compared to a national, full ensemble run at 100m). Using the simulated changes at 100m resolution from those models as training data, combined with a set of covariates including the simulated changes in 500m resolution, Random Forest (RF) algorithms were trained to downscale simulated changes from 500m to 100m.

Generalizing the trained RF algorithms, Denmark-wide maps of expected climate change induced changes to the shallow groundwater table at 100m resolution were modelled. To verify the downscaling results, amongst others, the RF algorithms were successfully validated against results from a sixth hydrological subcatchment model at 100m resolution not used in training the algorithms.

The experience gained also opens for various other applications of similar algorithms where computational limitations inhibit running distributed hydrological models at fine resolutions: The results suggest the potential to downscale other model outputs that are desired at fine resolutions.
Preliminary sedimentological investigation of a Holocene lake deposit in the northern Apennines (Italy)
Authors: Morandi Lionello , Segadelli Stefano , Cocuccioni Marco
Published: March 2021

The lake Moo in the northern Apennines, a 0.15 km2 basin located at an altitude of 1130 m a.s.l., consists of a small marshy area lying within a portion of a flat semi-circular depression surrounded by steep slopes. The site presents a series of geological and geomorphological characteristics which make it an ideal context to observe the results of flood events on the late Holocene sedimentary record of the basin. Our project aims to establish a relationship between recent deposits, instrumental data and modern-age cartography, in order to obtain site-specific parameters to interpret the sedimentary signal produced by floods on our site. The information can be extended back in time to the millennial scale by analysing sediment cores, in order to observe the frequency and magnitude of flood events throughout the Holocene and assess potential relationships with palaeoclimate reconstructions. This contribution discusses the results from five coring campaigns undertaken between 2018 and 2019 for a total thickness of 10.5 m, which allowed the recording of a c. 500 m long transect stretching from the west slope to the open water on the eastern part of the basin. This extended section enhanced our understanding of the deposit on a larger scale, allowing us to relate the new sequences to the ones identified in previous cores, and develop insights into flood-induced sediment gravity flows and their macroscopic physical characteristics (i.e. grain size, sedimentary structures, Munsell colour and types of contact surfaces). The study has led to the observation of possible correlations between various flood events and Holocene periods.
Assessing the wildfire activity in protected areas of the Amazon basin
Authors: Da Ponte Emmanuel , Alcasena Fermin , Bhagwat Tejas , Hu Zhongyang
Published: March 2021

Despite  growing concerns regarding the Amazonian wildfires, the magnitude of the problem is poorly understood. In this study, we assessed the wildfire activity in the  protected natural sites (n= 428) of Bolivia, Brazil, Colombia, Ecuador, French Guyana, Guyana, Peru, Suriname, and Venezuela, encompassing an area of 1.4 million km2 of the Amazon basin. A 250 m resolution spectroradiometer sensor imaging (MODIS) was used to obtain land-use/land-cover (MODIS land use land cover product) changes and derive the wildfire activity data (ignition locations and burned areas (MODIS active fire products)) from 2001 to 2018. First, we characterized the mean fire return interval, wildfire occurrence, and empiric burn probability. Then, we implemented a transmission analysis to assess the burned area from incoming fires. We used transmission analysis to characterize the land use and anthropic activities associated to fire ignition locations across the different countries. On average, 867 km 2 of natural forests were burned in protected natural sites annually, and about 85 incoming fires per year from neighboring areas accounted for 10.5% (9,128 ha) of the burned area. The most affected countries were Brazil (53%), Bolivia (24%), and Venezuela (16%).Considerable amount of fire ignition points were detected in open savannas (29%) and grasslands (41%) , where the fire is periodically used to clear extensive grazing properties. The incoming fires from savannas were responsible for burning the largest forest areas within protected sites, affecting as much as 9,800 ha in a single fire event. In conclusion, we  discuss the potential implications of the main socioeconomic factors and environmental policies that could explain increasing trends of burned areas. Wildfire risk mitigation strategies include the fire ignition prevention in developed areas, fire use regulation in rural communities, increased fuels management efforts in the buffer areas surrounding natural sites, and the early detection system that may facilitate a rapid and effective fire control response. Our analysis and quantitative outcomes describing the fire activity represent a sound science-based approach for an well defined wildfire management within the protected areas of the Amazonian basin.
Investigating glacial and postglacial sediment deposition and relative sea level changes at Ruddons Point, Fife, Scotland
Authors: Boyd Sarah , Bates Richard , Kinnaird Tim , Raub Tim , Srivastava Aayush
Published: March 2021

Ruddons Point, situated on the Firth of Forth coastline, Scotland, is a laterally extensive terrace of glacial and marine sediment deposits which are raised above current sea level. The deposits are situated near to Kincraig Point, a key site that records a series of stepped erosional platforms carved into the local tuff and agglomerate bedrock, representing a series of post Last Glacial Maximum (LGM) paleoshorelines. The raised marine deposits of Ruddons Point are composed of sand, shell, gravel and cobble horizons, which have been deposited unconformably on glacial tills and clays. 1km inland, incised by a small stream (the Cocklemill Burn), numerous cut banks reveal further raised deposits. Previous attempts to date these sediments have produced conflicting depositional histories, with no clear correlation to the Kincraig Point paleoshorelines or those dated further west along the Forth Valley. To this end, a multidisciplinary study was conducted to provide a detailed geochronology and interpretation of this diverse field area, ranging from the dating of glacial clays, thought to be deposited during the early phases of sedimentation leading up to the LGM, through to establishing the timing of marine sediment deposition in the Mid to Late Holocene. Geophysical electrical surveys were employed to supplement the subsurface investigations of the shore and adjacent saltmarsh and to aid construction of a sedimentary deposition model. Optically stimulated luminescence dating and radiocarbon dating were carried out on selected samples through the raised deposits and subsurface cores to provide a chronometric framework. Results demonstrate that subsurface clay horizons date to ~29 ka, indicating deposition at the onset of the last glacial. Inland raised deposits along the Cocklemill Burn preserve periods of sedimentation ranging from ~8.5 ka to ~4.5ka, and suggest a punctuated rise in sea level during the Mid Holocene. The nearshore raised sands and gravels of Ruddons Point are dated to ~3.5ka, deposited during a period of relative sea level (RSL) fall in the Late Holocene. The study concludes that the combination of detailed fieldwork, geophysical survey and dating allow the scope for complex landscape changes to be identified and further the understanding of the interplay between glacial isostatic adjustment and RSL changes across the postglacial coastlines of Fife.

 
Impact sporadic sources of disturbances on the atmospheric electric field оn Tien- Shan
Authors: Antonova Valentina , Kryukov Sergey , Lutsenko Vadim , Malimbayev Andrey
Published: March 2021

Results of the study of the impact of sporadic sources of disturbances on the state of the atmospheric electric field at the high-mountain Tien Shan station (3340 m above sea level, 20 km from Almaty) are presented. The absence of unitary variation (Carnegie curve) is the characteristic feature of diurnal changes in the atmospheric electric field under good weather conditions.

The most geoeffective sporadic sources of disturbances in the near-Earth space and the Earth's atmosphere are giant coronal mass ejections (CME), accompanied by Forbush effects in the intensity of galactic cosmic rays and by geomagnetic storms. Our studies were carried out taking into account the peculiarities of CME manifestations in the atmosphere and magnetosphere of the Earth. It was found that large magnetic storms affect the average level of the atmospheric electric field (increasing or decreasing it due to a change in the rigidity of the geomagnetic cutoff Rc), and also cause its fluctuations in the minute range (10-3 ÷ 10-2) Hz. A significant decrease in the atmospheric electric field after CME is due to large Forbush effects during weak geomagnetic disturbances.

Anomalous changes in the atmospheric electric field on the eve and during earthquakes were recorded, which are unambiguously associated with the activation of seismic processes. Since the city of Almaty is surrounded by a number of potential sources of strong earthquakes, the problem of their prediction is actual for the city and its environs.
Unprecedented summertime daily rainfall across the UK
Authors: Kent Chris , Dunstone Nick , Tucker Simon , Scaife Adam , Kendon Elizabeth , Brown Simon , Smith Doug , Greenwood Shirley , McLean Lynsay
Published: March 2021

The UNSEEN (UNprecedented Simulated Extremes using ENsembles) method involves using a large ensemble of initialised climate model simulations to increase the sample size of rare events. In this work we extended UNSEEN to focus on intense summertime daily rainfall events. Specifically, plausible extreme rainfall scenarios were developed to help understand potential surface water flooding impacts, and ultimately better inform flood management and resilience across the UK. To help address modelling limitations a large ensemble of simulations from two climate models were used; an initialised 25km global model that uses parametrized convection, and a dynamically downscaled 2.2km model that uses explicit convection. Climate model fidelity was assessed using a regional pooling technique based on extreme value theory. Across much of the UK both models are indistinguishable from the observations in terms of the statistical characteristics which govern the magnitude of very rare return periods. The UNSEEN analysis provides new estimates of plausible extreme return levels (i.e. 1-in-1000 year) across the UK and can reduce uncertainty in the expected frequency of very rare events by 50-70% compared to estimates using observations alone. These results enable suitable observed rainfall profiles to be uplifted to plausible extreme return levels, which can then be used within regional hydrological models to stress test surface flooding scenarios. The annual chance of unprecedented daily rainfall events in the current climate is also quantified, and found to be up to 5% (1-in-20 year return level) for many grid cells across southern parts of the UK. Finally, a significant benefit of the UNSEEN approach over purely statistical emulators is the use of dynamical climate models which allow the large-scale dynamical drivers of extreme daily summertime rainfall to be assessed.
Mapping the outdoor effective dose: the case study of the Umbria region (Italy)
Authors: Serafini Andrea , Albéri Matteo , Bisogno Stefano , Chiarelli Enrico , Cicala Luca , De Cesare Mario , Maino Andrea , Montuschi Michele , Motti Andrea , Natali Norman , Ogna Marco , Raptis Kassandra Giulia Cristina , Simone Gianluigi , Strati Virginia , Mantovani Fabio
Published: March 2021

The absorbed dose rate due to natural radioactivity arises from terrestrial and cosmic sources, both contributing to the individual effective dose rate per fraction of time spent outdoor. Rocks and soils are the main reservoirs of terrestrial gamma-emitting radionuclides (e.g. 40K and radioisotopes of the 232Th and 238U chains) while high-energy particles originated from astrophysical phenomena produce a cascade of nuclear interactions which contributes to cosmic radiation decreasing in intensity with the atmosphere depth. Following the UNSCEAR 2008 report, the average exposure of the world population to the different natural radioactivity sources corresponds to about 2420 μSv/yr and the external effective dose of terrestrial and cosmic origin is 870 μSv/yr.

The Umbria region (Italy), with its high variability of sedimentary and igneous rocks (e.g. limestone, sandstone, volcanic tuff) and a population of about 880000 inhabitants well distributed between 100 m and 1000 m a.s.l., represents the ideal case for mapping the effective dose from natural sources in a multifaceted environment. The outdoor effective dose rate from terrestrial radionuclides is studied by analysing 7439 gamma spectra measuring rock and soil samples in laboratory and carrying out about 20 hours of airborne radiometric surveys. Collocated CoKriging is used for the spatial interpolation of the sparse data, adopting a high-resolution geological map as ancillary information. The obtained numerical map is integrated with the cosmic radiation effective dose rate calculated considering the effects of altitude, latitude and the solar magnetic activity cycle. The resulting map of the outdoor effective dose rate shows a median value of 632 mSv/yr and only 3% of the territory is characterized by values higher than 814 mSv/yr.