bluuebunny/crossref_metadata_2025 huggingface dataset:
The blackout of September 2019 on the island of Tenerife: an opportunity to estimate the level of contamination of electromagnetic noise using the magnetotelluric method
Authors: Martínez van Dorth David , D'Auria Luca , Ledo Fernández Juanjo , Piña-Varas Perla , Di Paolo Federico , Cabrera-Pérez Iván , Cervigón Germán , Przeor Monika , Hernández William , Queralt Pilar , Marcuello Alejandro , Pérez Nemesio
Published: March 2020

The magnetotelluric method (MT) is a geophysical technique that provides high resolution information of the electrical resistivity of the subsurface geological structures by measuring the natural variations of the electromagnetic field recorded on the surface. Among the numerous applications, it can be used to map the presence of fluid reservoirs and localize significant structural contrasts that could be related to the presence of a geothermal or volcanic system. However, the interference of the anthropogenic noise during the MT measurements could affect significantly the correct interpretation of the collected data.

For this reason, in order to evaluate the effect of data contamination by anthropogenic sources, we analyzed the data registered by a continuous recording magnetotelluric station located inside the caldera of Las Cañadas (Tenerife, Spain). The instrumentation consisted of an ADU-08e, equipped with EPF-06 electrodes and MFS-06 magnetic coils. Two electric (Ex, Ey) and three magnetic (Hx, Hy, Hz) components have been recorded. This geophysical station was installed by the Instituto Volcanológico de Canarias (INVOLCAN), with purposes of volcano monitoring, on June 2019 and since then it has been recording data daily in the frequency range of 0.001 – 1000s.

On September 29 (2019) a significant electric blackout took place in the entire island of Tenerife in which, during approximately 6 hours the electricity supply was completely shut down. This situation represented a clear opportunity to obtain raw data almost free of anthropogenic contamination and it could help to quantify the effect of the anthropogenic noise in the MT measurements performed in a densely urbanized area as Tenerife. The first results show the clear change at 13:11:39 local time (GMT) in which both the electrical and magnetic components evidenced a pronounced change in their temporal pattern. Moreover, the comparison of the impedance tensor components between the previous hours and during the blackout reveals a noticeable difference for periods higher than 1 s.
Databased simulation and reconstruction of the near shore geomorphological structure and sediment composition of the German tidal flats
Authors: Sievers Julian , Milbradt Peter , Rubel Malte
Published: March 2020

With an area of almost 10,000 km², the project area represents the tidal flats on Germany’s North Sea coast. The tidal flats and their channels as well as morphologically highly active estuarine systems undergo significant erosional and sedimentational processes that prove difficult the assessment of sedimentological composition based on relatively few and temporally far stretched field measurements. The holistic databased simulation of both the internal structure of the soil itself and its sedimentary composition is based on around 21,000 measured surface sediment samples (from 1949 until recent) and yearly consistent digital bathymetric models, starting 1950, spatiotemporally interpolated in a 10 m grid resolution by the Functional Seabed Model. By utilizing the high temporal and spatial resolution of the bathymetric models, it is possible to quantify the seabed depth evolution (sedimentation and erosion) and to solve a differential equation to capture sedimentary evolution, a consistent and continuous three dimensional model of both the surface and the subsurface structures and sedimentary compositions can be generated. To further extend the volumetric extent of the model, around 16,000 sedimentary core samples are used to fill the spatial and consequently the temporal void between the lowest altitudinal range of validity of the aforementioned model segment to the lower boundary of the target model volume. This boundary is set to be the lower limit of the morphologically active or activatable space, which contains the volume of sediment that could be eroded in current climate conditions. The limit, generally speaking, can be expected to somewhat coincide with the base of Holocene sediments, as Pleistocene sediments – especially subglacial tills – generally take higher amounts of bottom shear stress to erode than unindurated Holocene sediments, which usually form tidal flat sediments. The purpose of the generated three dimensional model is to be able to derive sedimentological information in both custom spatial resolution as well as custom sedimentological classification as base and validation data for process based morphodynamic simulation models. With these enhanced models, the quality of the prognosis of morphological developments and stability of coastal areas as a tool for planning processes for coastal protection and maritime economy is expected to be increased.
Spatio-Temporal Dynamics of East Asia Atmospheric Rivers and their Atmospheric Steering and Climatic Regulation
Authors: Pan Mengxin , Lu Mengqian , Lall Upmanu , Dong Qizhen
Published: March 2020

The identification, climatic modulation and hydrological impact of Atmospheric Rivers (ARs) is an emergent scientific topic in recent years. ARs are important and yet understudied for East Asia (EA). We use our new AR identification algorithm (Pan & Lu, 2019), to build up a comprehensive AR catalog for this region for the first time.  Interesting patterns are found: (1) there is a dominant AR route, originating from the Arabian Sea, crossing over the Bay of Bengal and Indochina, South China Sea (SCS) and Southeast China (SEC), and terminating in the western North Pacific; and (2) a nine-stage annual pattern in the climatological frequency is revealed.  Stage 1: mid-Mar to mid-May, the formation of Western North Pacific Subtropical Height (WNPSH) near the SCS steers and confines AR in its northwest flank over SEC.  Stages 2-5: during the monsoon season from mid-May to late-Aug, the evolution of AR follow the intra-seasonal progression of Asia-Pacific monsoon (including South Asian monsoon, East Asian monsoon and western North Pacific monsoon. Stages 6-9: late-Aug to mid-Mar, ARs leave EA and only occur over the North Pacific. Over all stages, we find the contribution of AR grows significantly with more extreme rainfall (i.e., from the annual rainfall, heavy rainfall, persistent heavy rainfall to large spatial extent persistent heavy rainfall), especially in spring and early-monsoon season. This emphasizes ARs’ significant role in extreme or catastrophic rainfall events. Intriguingly, divergence of AR trajectories (also in their characteristics) occurs along the extratropical direction, and such divergent features have spatially heterogenous dependence on the leading modes of a collection of steering atmospheric and regulating climatic signals. Large divergence indicates high sensitivity of AR to transient steering; while small divergence promises high predictability of ARs, thus their associated hydrological impacts.
Waveguidability of idealized midlatitude jets and the limitations of ray tracing theory
Authors: Wirth Volkmar
Published: March 2020

Ray paths of stationary Rossby waves emanating from a local mid-latitude source are usually refracted equatorward. However, this general tendency for equatorward propagation is mitigated by the presence of a midlatitude jet which acts as a zonal waveguide. This opens the possibility for circum-global teleconnections and quasi-resonance, which suggests that the ability of a jet to guide a wave in the zonal direction is an important property.

This paper investigates waveguidability of idealized midlatitude jets in a barotropic model on the sphere. A forced-dissipative model configuration with a local source for Rossby waves is used in order to quantify waveguidability by diagnosing the latitudinal distribution of waviness in a longitudinal sector far downstream of the forcing. Systematic sensitivity experiments show that waveguidability increases smoothly with increasing jet amplitude and with decreasing jet width. This result is contrasted with the predictions from two idealized theoretical concepts based (1) on ray tracing as derived from WKB theory and (2) on a sharp jet with a zonally oriented front of potential vorticity. The existence of two so-called turning latitudes, which is the key diagnostic for a zonal waveguide according to ray tracing theory, turns out to be a poor predictor for the dependence of waveguidability on jet amplitude and jet width obtained in the numerical simulations. By contrast, the meridional gradient of potential vorticity correlates fairly well with the diagnosed waveguidability. The poor prediction from ray tracing is not surprising, because the underlying WKB assumptions are not satisfied in the current context.
Dissolved organic matter in two thermal springs of East African rift valley
Authors: Butturini Andrea , Herzsprung Peter , Lechtenfeld Oliver , Venturi Stefania , Amalfitano Stefano , Olaka Lydia , Pacini Nic , Harper David , Tassi Franco , Fazi Stefano
Published: March 2020

Little is known about dissolved organic matter (DOM) in thermal springs. To fill this gap, this study describes the quantity, optical and molecular properties of dissolved organic matter (DOM) in two geothermal springs located in the East African rift valley a region extremely rich in geothermal phenomena such as hot springs, fumaroles, geysers and spouting springs and solfataras. The two sampled hot springs are located at the south of Elmentatia soda-saline lake and at the Ol Njorowa gorge. Results evidenced the abundance of reduced, saturated, little aromatic compounds that might reflect DOM altered by high temperature and pressure. Beside that, the two hots springs showed very clear distinctive signatures. At Ol Njorowa the most abundant molecules are oxygen poor and sulphur bearing like molecules which might reflect abiotic sulfurization from geo fluids rich in H2S. In contrast Elmentatia hot spring is characterized by abundant nitrogen bearing aliphatic and protein-like molecules probably mirroring perfusion of geo-fluids through organic rich sediments located below the Elmentaita lake bottom.
Precursors and processes culminating in the Anak Krakatau December 2018 sector collapse and tsunami
Authors: Walter Thomas R. ,   Rapid Response Team
Published: March 2020

It is 135 years after the 1883 volcano-triggered tsunami disaster, when Krakatau volcano became once more the source of a deadly tsunami striking without warning. We use data recorded on the ground and by satellite, to show that the volcano was in an elevated stage of activity throughout the year 2018, producing thermal anomalies associated with volcanic deposits, an increase of the island area and ground movement of the southwestern sector of the island towards the sea, increasing in June 2018. Following further intense activity on 22 December 2018, seismic data reveal the timing and duration when this sector collapsed. The landslide removed 102 million m³ of material subaerially, which was followed by ~15 minutes of phreatic explosions. This study allows better understanding of the complex hazard cascades, including precursory thermal anomalies, island growth and deformation, followed by sector collapse, tsunami waves, and finally explosive volcanic eruptions, and has important implications for designing early warning systems.
Aggregation of Spatial Extremes
Authors: Richards Jordan , Tawn Jonathan
Published: March 2020

Fluvial flooding is caused by excessive rainfall sustained over extended periods of time and over spatial catchment areas. Although methodology for modelling excessive, or extreme, rainfall events is extensive and well researched, the same cannot be said about how the extremal properties of spatial and temporal aggregations of rainfall are related. We hope to rectify this by developing a methodology for modelling extremes at different spatio-temporal scales and which incorporates a wide range of dependence structures.

Research on modelling aggregated spatial extremes is ongoing, but here we present some interesting first-order behavior for the tails of aggregates of (dependent) variables. Marginally these variables are assumed to have GPD tails and we focus on exploring how properties of the dependence structure influence the tail properties of the aggregate. The implications of our theoretical results for statistical purposes will be discussed.

 
Connecting the dots: Multi-point observations for solar wind science and forecasting
Authors: Owens Mathew
Published: March 2020

Atmospheric science and forecasting, concerned with a volume ~1013 m3, is underpinned by an extensive observational network; point measurements at 10k land-based stations, 4k ships and buoys, and around 1k dedicated balloon launches and aircraft; remote sensing from hundreds of radars and 10 dedicated operational satellites providing independent “look directions” through the atmosphere. By comparison, the heliosphere is a vastly under-sampled system. In the ~1028 m3 volume contained within Earth orbit, there has been a maximum of 5 simultaneous point measurements and remote sensing from (at most) 3 simultaneous vantage points. This makes it difficult to reliably interpret observations in terms of the 3-dimensional structure and extent of solar wind transients. Solar Orbiter, Parker Solar Probe, STEREO-A and L1 monitors (and a possible future L5 monitor), as well as more limited solar wind measurements from planetary/cometary missions, will shortly provide unprecedented observational coverage and thus a unique opportunity to better understand solar wind transients. Nevertheless, sampling will remain sparse and connecting point observations and interpreting remote sensing observations will remain ambiguous. Global models of the solar wind can aid greatly in this regard. This talk will summarise how observations and models can be best combined to exploit the strengths of both, and what we can learn about solar wind transients.
Quantifying CME arrival time uncertainty with mega ensembles
Authors: Owens Mathew
Published: March 2020

Near-Earth solar wind conditions, including disturbances generated by coronal mass ejections (CMEs), are routinely forecast using 3-dimensional, numerical magnetohydrodynamic (MHD) models of the heliosphere. The resulting forecast errors are largely the result of uncertainty in the near-Sun boundary conditions, rather than heliospheric model physics or numerics. Thus ensembles of heliospheric model runs with perturbed initial conditions are used to estimate forecast uncertainty. MHD heliospheric models are relatively cheap in computational terms, requiring tens of minutes to an hour to simulate CME propagation from the Sun to Earth. Thus such ensembles can be run operationally. However, ensemble size is typically limited to ~101-102, which may be inadequate to sample the relevant high-dimensional parameter space. Here, we describe a simplified solar wind model that can estimate CME arrival time in approximately 0.01 seconds on a modest desktop computer and thus enables significantly larger ensembles. It is a 1-dimensional, incompressible, hydrodynamic model, which has previously been used for the steady-state solar wind, but is here used in time-dependent form. This approach is shown to adequately emulate the MHD solutions to the same boundary conditions for both steady-state solar wind and CME-like disturbances. We suggest it could serve as a “surrogate” model for the full 3-dimensional MHD models. For example, ensembles of ~105-106 members can be used to identify regions of parameter space for more detailed investigation by the MHD models. Similarly, the simplicity of the model means it can be rewritten as an adjoint model, enabling variational data assimilation with MHD models without the need to alter their code. Model code is available as an Open Source download in the Python language.
The geodiversity of loess sequences in the Po plain (Northern Italy): scientific values, threats, and promotion opportunities
Authors: Bollati Irene Maria , Zerboni Andrea
Published: March 2020

Quaternary loess deposits and complex pedosequences developed on wind-blown silt as parent material are very powerful palaeoclimatic and palaeoenvironmental indicators allowing the reconstruction of glacial/interglacial cycles. For this relevant scientific value, loess outcrops are gaining great attention in the framework of geoheritage valorisation. Loess sequences are distributed along wide latitudinal ranges in both the Boreal and Austral Hemispheres, but they are less frequent if compared to other kinds of Quaternary sediments, and often characterized by a hotspot-like distributions. They are, hence, key-points in geodiversity assessment at basin-scale. Strategies balancing geoconservation and promotion are hence required, and they should be based on the assessment of sites specific values and threats sites may undergo. Loess sequences, in fact, are geosites of stratigraphic interest and geomorphosites that may suffer geomorphic processes (e.g., pedogenesis, linear erosion, tectonics, slope deformation and erosion) threatening their existence. The same processes, at the meantime, are generating spectacular landscapes. Besides the most famous Chinese loess plateau, the North and South American loess basins, and the central Eurasian loess belt, several other minor loess basins are distributed in the world. Among these areas, we can consider the Mediterranean loess areas, and especially the Upper Pleistocene Po Plain Loess Basin of Northern Italy. The latter includes several loess/paleosols outcrops displaying complex pedosequences formed under contrasting Pleistocene pedoclimatic settings, recording recent tectonic activity between the foreland of the Alpine and Apennine ranges (i.e., site-scale geodiversity), and preserving open-air Palaeolithic archaeological sites (i.e., cultural value). After examining the global values of and the potential threats to loess geosites, as proposed in the current literature, a detailed analysis on the potentialities (in terms of scientific features, values, threats, geoconservation, and promotion strategies) of a selection of loess sites from the Po Plain Loess Basin is proposed. The quantification of the values of the geosites is performed considering the global value (i.e. scientific and additional values) of loess-bearing sites and the potential for use, according to a methodology based on a database, already tested in similar thematic contexts. In particular, this methodology implies the geodiversity assessment at site-scale, and this is particularly relevant for loess sites. Finally, for each locality, tips for enhancing Italian loess sites through promotion and geoconservation are provided.
The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6
Authors: Goelzer Heiko ,   The ISMIP6 team
Published: March 2020

The Greenland ice sheet is one of the largest contributors to global-mean sea-level rise today and is expected to continue to lose mass as the Arctic continues to warm. The two predominant mass loss mechanisms are increased surface meltwater runoff and mass loss associated with the retreat of marine-terminating outlet glaciers. In this paper we use a large ensemble of Greenland ice sheet models forced by output from a representative subset of CMIP5 global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The simulations are part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate the sea-level contribution together with uncertainties due to future climate forcing, ice sheet model formulations and ocean forcing for the two greenhouse gas concentration scenarios RCP8.5 and RCP2.6. The results indicate that the Greenland ice sheet will continue to lose mass in both scenarios until 2100 with contributions of 89 ± 51 mm and 31 ± 16 mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largest mass loss is expected from the southwest of Greenland, which is governed by surface mass balance changes, continuing what is already observed today. Because the contributions are calculated against a unforced control experiment, these numbers do not include any committed mass loss, i.e. mass loss that would occur over the coming century if the climate forcing remained constant. Under RCP8.5 forcing, ice sheet model uncertainty explains an ensemble spread of 40 mm, while climate model uncertainty and ocean forcing uncertainty account for a spread of 36 mm and 19 mm, respectively. Apart from those formally derived uncertainty ranges, the largest gap in our knowledge is about the physical understanding and implementation of the calving process, i.e. the interaction of the ice sheet with the ocean.
Precipitation projections of the first multi-model ensemble of regional climate simulations at convection permitting scale
Authors: Pichelli Emanuela , Coppola Erika , Ban Nikolina , Giorgi Filippo , Stocchi Paolo , Alias Antoinette , Belušić Danijel , Berthou Segolene , Caillaud Cecile , Cardoso Rita M. , Chan Steven , Christensen Ole Bøssing , Dobler Andreas , de Vries Hylke , Goergen Klaus , Kendon Elizabeth J. , Keuler Klaus , Lenderink Geert , Lorenz Torge , Mishra Aditya N. , Panitz Hans-Juergen , Schär Christoph , Soares Pedro MM. , Truhetz Heimo , Vergara-Temprado Jesus
Published: March 2020

We present a multi-model ensemble of regional climate model scenario simulations run at scales allowing for explicit treatment of convective processes (2-3km) over historical and end of century time slices, providing an overview of future precipitation changes over the Alpine domain within the convection-permitting CORDEX-FPS initiative. The 12 simulations of the ensemble have been performed by different research groups around Europe. The simulations are compared with high resolution observations to assess the performance over the historical period and the ensemble of 12 to 25 km resolution driving models is used as a benchmark.

An improvement of the representation of fine scale details of the analyzed fields on a seasonal scale is found, as well as of the onset and peak of the summer diurnal convection. An enhancement of the projected patterns of change and modifications of its sign for the daily precipitation intensity and heavy precipitation over some regions are found with respect to coarse resolution ensemble. A change of the amplitude of the diurnal cycle for precipitation intensity and frequency is also shown, as well also a larger positive change for high to extreme events for daily and hourly precipitation distributions. The results  are challenging and promising for further assessment of the local impacts of climate change.
Hydrochemical evaluation of a groundwater system connected to a wetland: A case study in the Seyfe Lake wetland, Kirsehir, Turkey
Authors: Yurteri Cansu
Published: March 2020

Abstract

Wetlands play an important role in the hydrologic cycle and are also regarded as major water reservoirs. Hydrochemistry application is an important tool which enables the evaluation of water type, water-rock interactions, discharge and recharge mechanism of wetlands. The aim of this study is to clarify the hydrogeochemical processes involving recharge and discharge mechanism of the wetland system and determine the hydrochemical characteristics of the wetland water, based on groundwater and surface water chemistry data. Within this scope; a detailed geological, hydrological, hydrogeological, hydrochemical and isotopic studies were performed in the Seyfe Lake catchment. Seyfe Lake and its surroundings, which is located in Mucur district, approximately 16 km northeast of Kirsehir, Turkey, is a first degree natural reserve and Ramsar Site. First field campaign was carried out in September 2019 and twenty three sampling points were selected in the study area. Sampling points were chosen from the wetland area and wells and springs that are located in the recharge area. Physicochemical parameters such as pH, specific electrical conductivity, temperature and discharge rates of the water samples were measured in-situ. Temperature, specific electrical conductivity and pH of the water samples ranges from 14.5°C to  21.2°C, from 370 µS/cm to 30500 µS/cm and from 7.15 to 8.65, respectively. Discharge rate of the springs are between 0.02 and 1 l/s. These waters have neutral to slightly alkaline character. Stable isotopes and hydrochemistry are used to identify possible recharge areas, origin of waters, groundwater-surface water relation and water-rock interactions. The δ2H and δ18O values of the water samples ranges between -27.61‰ to -80.88‰, and -11.97‰ to 0.86‰, respectively in the Seyfe wetland area. The results of this study will contribute to a better understanding of groundwater dynamics and hydrochemical processes in the wetland area.

Key words: Hydrochemistry, Stable isotopes, Wetland, Ramsar site, Seyfe Lake, Kirsehir
Analysis of long-term catchment data: a nonlinear perspective
Authors: Lange Holger , Hauhs Michael , Funk Katharina , Sippel Sebastian , Meesenburg Henning
Published: March 2020

We analyze time series from several forested headwater catchments located adjacent to each other in the Bramke valley, Harz mountains (Germany) which are monitored since decades for hydrology, hydrochemistry and forest growth. The data sets include meteorological variables, runoff rates, streamwater chemical concentrations, and others. The basic temporal resolution is daily for hydrometeorology and two-weekly for streamwater chemistry (in addition, standing biomass of a Norway spruce stand is measured every couple of years).

A model was calibrated and run for the streamflow from one of the catchments, based on precipitation, temperature and (simulated) evapotranspiration of the growing trees, to elucidate the effect of forest growth on catchment hydrology.

The catchments exhibit long-term changes and spatial gradients related to atmospheric deposition, management and changing climate. After providing a short multivariate summary of the dataset, we present several nonlinear metrics suitable to detect and quantify subtle changes and to describe different behavior, both between different variables from the same catchment, as well as for the same variable across catchments. The methods include, but are not limited to: Tarnopolski analysis, permutation entropy and complexity, q- and α-complexities, and Horizontal Visibility Graphs.

The detection of these changes is remarkable, because linear trends have already been removed prior to analysis. Hence, their presence reflects intrinsic changes in the patterns of the time series. The metrics also allow for a detailed model evaluation from a nonlinear perspective.

An important methodological aspect is the temporal resolution of the time series. We investigate the scaling behavior of the nonlinear metrics through aggregation or decimation to coarser resolutions and conclude on what the scaling behavior may imply for inverse (hydrological) modelling tasks.
PHUSICOS platform: Nature-based solutions to reduce risk in mountain landscapes
Authors: Baills Audrey , Bernardie Severine , Frezot Olivier , Marquis Gaelle ,   PHUSICOS Team
Published: March 2020

PHUSICOS platform aims at gathering nature-based solutions (NBS) relevant to reduce hydro-geological risks in mountain landscapes. The platform can be accessed directly through a web portal It is based on an Open Source CMS website, including a filer to store documents and a map server to bring ergonomic and powerful access. Furthermore, a list of metadata has been proposed to structure the information. These metadata have provided the baseline for database content and the platform has been filed with the literature review of existing NBSs related to extreme hydro-meteorological events. In particular this review integrates existing case studies presented in existing platforms. That is why PHUSICOS platform has been built to be coherent with these platforms. Nine platforms were identified during the inventory of NBSs of interest for PHUSICOS: Oppla, Think Nature, NAIAD, The European Climate Adaptation Platform (CLIM-ADAPT), Urban Nature Atlas, Prevention Web, Adaptation Community, PANORAMA – Solutions for a Healthy Planet and RECONNECT.

Contribution to PHUSICOS platform is open to registered users. A questionnaire based on relevant data, necessary for the definition and identification of the NBS (metadata, to be used for searching the NBSs within the platform) has been defined to enter new entries. Next step will be the implementation of the evaluation for providing a ranking list of NBS according to a multi-criteria approach.

The platform now gathers 46 entries and will be enriched all along the project, in particular with NBS that will be implemented in PHUSICOS demonstrator sites: the Serchio River Basin (Italy), the Valley of Gudbrandsdalen (Norway) and the Pyrenees (Spain-France-Andorra).

The full structure of the platform and preliminary content are presented in this work.
Impacts of model spatial resolution on intense and heavy precipitation events over the Mediterranean region.
Authors: Conte Dario , Lionello Piero , Gualdi Silvio
Published: March 2020

Dynamical downscaling through coupled regional climate model plays an important role to improve climate information at regional fine-scale, since it modulates information produced by GCM, combining planetary scale processes with regional scale processes.  This study describes the impact of climate change  on rainfall over the Mediterranean region, downscaling, at two different horizontal grid resolutions (0.44 and 0.11 degs), a Global Climate Model (GCM at 0.75 degs) by means of a coupled Regional Climate System Models (RCSM). We analyze the effect of adopting model version with different horizontal resolutions (0.11, 0.44 e 0.75 degs), considering  two climate representative concentration pathways (rcp4.5 and rcp8.5). The spatial pattern on different aspects of precipitation climatology are investigated such as increase/decrease in the intensity of precipitation events, extremes and annual amount of wet days. Moreover, since the grid models cover a wide and complex climate geographic area, the rainfall probability over six sub-regions are calculated: (1) Alps, (2) North-Western coast, (2) South Italy, (3) central part of the Mediterranean sea, (4) Greece Anatolia peninsula and Levantine basin. Although, the evaluation of RCSM downscaling is complex and depends on several factors such as: variables considered, geographic area, topography, model configuration and so on, the results show that it produces an significant improvement, adding information with regards to fine-scale spatial pattern, respect to that provided by GCM.

ACKNOWLEDGEMENT: This contribution is based on work conducted by the authors within the SOCLIMPACT project, that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 776661. The fullname of the project is "DownScaling CLImate ImPACTs and decarbonisation pathways in EU islands, and enhancing socioeconomic and non-market evaluation of Climate Change for Europe, for 2050 and Beyond". The opinions expressed are those of the author(s) only and should not be considered as representative of the European Commission’s official position.

Keywords:  widespread heavy rainfall, coupled numerical models, daily rainfall, climate scenarios, climatology of heavy rainfall.

 
Electron acceleration in small-size magnetic holes
Authors: Liu Ji , Yao Shutao , Shi Quanqi , Wang Xiaogang , Zong Qiugang , Feng Yongyong , Liu Han , Guo Ruilong , Yao Zhonghua , Rae Jonathan Iain , Degeling Alexander William , Tian Anmin , Woodham Lloyd
Published: March 2020

The magnetic-to-particle energy conversion is one of the most fundamental physics processes to laboratory, space and astrophysical contexts. Adiabatic acceleration processes in moderate varying environment merely play significant roles to generate devastating cosmic rays and spectacular aurorae, etc. More commonly, when the violent variation or strongly inhomogeneity in electromagnetic field distorts the trajectory of the particles, non-adiabatic acceleration processes function more transiently and drastically on particle energization trigger explosive phenomena like sudden solar flares. However, without high-resolution simultaneous measurements on plasma and field at previous space missions, the small/fast scale of the non-adiabatic processes make it difficult to be analyzed to reach a comprehensive understanding to most of the underlying non-adiabatic acceleration mechanisms in space and astrophysical contexts. Here, using MMS data with unprecedented high temporal resolutions, we report such finding of acceleration for electrons trapped in a kinetic-size magnetic holes which at the same time is the acceleration region, and demonstrate the validity of the acceleration process by numerical simulation, achieving the reproduction for the observation.
Response of the North Atlantic circulation to the small-scale surface wind perturbations
Authors: Zhou Shenjie , Zhai Xiaoming , Renfrew Ian
Published: March 2020

High-frequency and small-scale processes in the atmosphere have an important influence on the evolution of the underlying ocean. They can not only introduce variability to the coupled systems but also have long-term ramification effects on the sea surface temperature, thermocline structure and large-scale ocean general circulation via nonlinear interactions.

Comparisons between the newly-released ECMWF fifth-generation global climate reanalyses (ERA5) wind product and satellite/in-situ observations show that the latest reanalyses winds still considerably underestimate wind variability at high-frequencies and small-scales. A novel approach, Cellular Automata (CA), is used here to stochastically perturb the ERA5 wind field. CA, originally introduced into the weather forecast model to mimic the near-grid-scale variability associated with convective cloud clustering, generates spatially and temporally coherent perturbation patterns. Results show that the CA-perturbed ERA5 wind field enjoys an improved wavenumber spectrum, especially over high wavenumber bands (scales <400 km), when compared to the QuikSCAT measurements. In addition, including CA patterns also brings the level of wind variability at high-frequencies (>1 cpd) closer to in-situ mooring measurements. The local response of the upper ocean properties is investigated by a Multi-Column K-Profile Parameterization (MC_KPP) ocean mixed layer model over Atlantic section. It is found that overall the sea surface temperature (SST) decreases and oceanic boundary layer (OBL) deepens to respond to the enhanced surface turbulent heat loss and shear instability generated at the base of surface OBL caused by the small-scale wind perturbations. In particular, SST tends to decrease the most over the summer hemisphere by up to 1°C locally and 0.1°C averaging across the basin, in correlation with shallower background OBL and smaller OBL heat capacity. 

The ocean states under the forcing of stochastic wind perturbation as expressed by the local response are found rectified by a non-negilible magnitude. We argued that although the missed small-scale and high-frequency wind variability may be represented differently than our approach, our results highlighted the fact that these variabilities should take a singificant part in driving the current generation of coupled climate model. Furhtermore, the temproal and spatial variabilities of the local signals can pose significant influence on the large-scale ocean circulation in terms of their pathways, strengths and variabilities. The dynamical response of the ocean circulation is to be further understood with an eddy-resolving Massachusette Institute of Technology General Circulation Model (MITgcm).
On the long term evolution of noctilucent clouds
Authors: Lübken Franz-Josef , Baumgarten Gerd
Published: March 2020

Some of the earliest observations in the transition region between the Earth's atmosphere and space (roughly at 80-120km) come from so called `noctilucent clouds' (NLC) which are located around 83km altitude and consist of water ice particles. They owe their existence to the very cold summer mesopause region (~130K) at mid and high latitudes. There is a long standing dispute whether NLC are indicators of climate change in the middle atmosphere. We use model simulations of the background atmosphere and of ice particle formation for a time period of 138 years to show that an increase of NLC appearance is expected for recent decades due to increased anthropogenic release of methane being oxidized to water vapor in the middle atmosphere. Since the beginning of industrialization the water vapor concentration at NLC heights has presumably increased by about 40 percent (1 ppmv). The water vapor increase leads to a large enhancement of NLC brightness. Increased cooling by enhanced carbon dioxide alone (assuming no water vapor increase) counter-intuitively would lead to a decrease(!) of NLC brightness. NLC existed presumably since centuries, but the chance to observe them by naked eye was very small before the 20th century, whereas it is likely to see an NLC in the modern era. The eruption of volcano Krakatoa in 1883 has seemingly triggered the first observation of an NLC in 1885. In this presentation we extend our analysis from middle to polar latitudes and expand comparison with observations.
Deglaciation of the Greenland and Laurentide ice sheets interrupted by glacier advance during abrupt coolings
Authors: Young Nicolas , Briner Jason , Miller Gifford , Lesnek Alia , Crump Sarah , Thomas Elizabeth , Pendleton Simon , Cuzzone Joshua , Lamp Jennifer , Zimmerman Susan , Caffee Marc , Schaefer Joerg
Published: March 2020

The early Holocene (11.7 ka to 8.2 ka) represents the most recent period when the Laurentide and Greenland ice sheets underwent large-scale recession. Moreover, this ice-sheet recession occurred under the backdrop of regional temperatures that were similar to or warmer than today, and comparable to those projected for the upcoming centuries. Reconstructing Laurentide and Greenland ice sheet behavior during the early Holocene, and elucidating the mechanisms dictating this behavior may serve as a partial analog for future Greenland ice-sheet change in a warming world. Here, we use 123 new 10Be surface exposure ages from two sites on Baffin Island and southwestern Greenland that constrain the behavior of the Laurentide and Greenland ice sheets, and an independent alpine glacier during the early Holocene. On Baffin Island, sixty-one 10Be ages reveal that advances and/or stillstands of the Laurentide Ice Sheet and an alpine glacier occurred in unison around 11.8 ka, 10.3 ka, and 9.2 ka. Sixty-two 10Be ages from southwestern Greenland indicate that the GrIS margin experienced re-advances or stillstands around 11.6 ka, 10.4 ka, 9.1 ka, 8.1 ka, and 7.3 ka. Our results reveal that alpine glaciers and the Laurentide and Greenland ice sheets responded in unison to abrupt early Holocene climate perturbations in the Baffin Bay region. We suggest that during the warming climate of the early Holocene, freshening of the North Atlantic Ocean induced by a melting Laurentide Ice Sheet resulted in regional abrupt cooling and brief periods of ice-sheet stabilization superimposed on net glacier recession. These observations point to a negative feedback mechanism inherent to melting ice sheets in the Baffin Bay region that slows ice-sheet recession during intervals of otherwise rapid deglaciation.
Reactive flow and homogenization in anisotropic media
Authors: Aharonov Einat , Roded Roi , Holtzman Ran , Szymczak Piotr
Published: March 2020

Dissolution by reactive fluid flow is a fundamental process in geological systems. It controls diagenesis and karst evolution and has broad implications for groundwater hydrology. Specifically, reactive flow controls the evolution of the void-space structure via the feedback between the reaction and transport. In some instances, advective transport rate is high compared to that of geochemical reactions (low Damkӧhler number, Da), such that the reactive fluid penetrates the system before its reactivity is exhausted, resulting in a relatively spatially-uniform dissolution. Despite the importance of low Da conditions, the emerging transformations in the medium structure, flow field, and its bulk properties are not well understood. Likewise, our ability to decipher diagenetic history and preexisting structure is lacking.

Here, using a network model, we investigate the evolution of heterogeneous and anisotropic medium during dissolution at low Da conditions. The numerical simulations show that the medium progressively becomes more homogeneous as well as isotropic, which consequently makes the flow field more uniform. Homogenization is particularly notable for anisotropic media, in which the transverse channels are wide relative to the channels parallel to the main flow direction. In this case, flow is initially focused within a few highly tortuous pathways, hence emphasizing the effect of dissolution on flow heterogeneity and tortuosity. The homogenization process is further enhanced when the surface reaction is transport-controlled—that is, when diffusion of dissolved ions away from the mineral surface to the bulk fluid is slow, reducing the reactivity adjacent to the surface: At first, since diffusive transport is more effective in narrow channels, they undergo faster dissolution, which selectively enlarges them leading to an initial steep rise in permeability. Later, however, as dissolution proceeds and the channels broaden, the overall dissolution rate drops, diminishing the growth rate of permeability. Our findings provide fundamental insights into reactive transport and hydrogeological processes in fractured and porous media.
Exploiting satellite technology and machine learning to describe and predict hazardous shoreline change
Authors: Rogers Martin
Published: March 2020

East Anglia is particularly vulnerable to sea level rise, increases in storminess, coastal erosion, and coastal flooding. Critical national infrastructure (including Sizewell’s nuclear power stations and the Bacton gas terminals), population centres close to the coastal zone (> 600,000 in Norfolk and Suffolk) and iconic natural habitats (the Broads, attracting 7 million visitors a year) are under threat. Shoreline change, driven by complex interactions between environmental forcing factors and human shoreline modifications, is a key determinant of coastal vulnerability and exposure; its prediction is imperative for future coastal risk adaptation.

An automated, python-supported, tool has been developed to simultaneously extract the water and vegetation line from satellite imagery. PlanetLab multispectral optical imagery is used to provide multi-year, frequent (up to fortnightly) images with 3-5m spatial resolution. Net shoreline change (NSC) has been calculated along multiple stretches of the East Coast of England, most notably for areas experiencing varying rates of change in front of, and adjacent to, ‘hard’ coastal defences. The joint use of water and vegetation line proxies enables calculation of inter-tidal width variability alongside NSC. The image resolution used provides new opportunities for data-led approaches to the monitoring of shoreline response to storm events and/or human shoreline modification.

Artificial Neural Networks (ANN) have been trained to predict shoreline evolution until 2040. Early results are presented, alongside considerations surrounding data pre-processing and input parameter selection requirements. Training data comprises decadal-scale shoreline positions recovered using automated shoreline detection. Shoreline position, alongside databases of nearshore bathymetry, sea defences, artificial beach renourishment, nearshore processes (wave and tide gauge data, meteorological fields), combined with land cover, population and infrastructure data act as inputs. Optimal input filtering and ANN configuration is derived using hindcasts.

The research is timely; ANN predictions are compared with the Anglian Shoreline Management Plans (SMPs), which identify locations at greatest risk and assign future risk management funding. The findings of this research will feed into future revisions of the plans.
On the role of CO2 in enhancing the temporal clustering of heavy precipitation across Europe
Authors: Yang Zhiqi , Villarini Gabriele
Published: March 2020

Heavy precipitation has increased across many areas of the world, not only in terms of amounts but also of intensity and frequency, causing billions of dollars in economic losses and numerous fatalities. Our ability to prepare for and adapt to these events is tied to our understanding of the physical processes responsible for these events, and how they may respond to changes in anthropogenic forcings. Here we focus on the temporal clustering of heavy precipitation across Europe, highlight what the major climate drivers responsible for it are, and how it may change in response to changes in the concentration of greenhouse gasses. More specifically, we use a peak over threshold approach to identify heavy precipitation events, and Cox regression to relate the occurrence of these events to four climate modes that have been connected with the occurrence of heavy precipitation across Europe: the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the East Atlantic (EA) pattern, and the Scandinavia pattern (SCAND). We use outputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5), and experiments that allow us to focus on the response to CO2 (pre-industrial, 1pctCO2, abrupt4×CO2). To further detect the effects of downscaling on model-simulated precipitation, we also considered the accuracy of the EURO-CORDEX regional climate model (RCM) on capturing the temporal clustering in heavy precipitation across Europe. We find that: 1) the CMIP5 models can capture the temporal clustering in heavy precipitation across Europe as a function of these four climate modes; 2) the increases in CO2 are expected to lead to a strengthening of the relationship between the climate modes and the occurrence of heavy precipitation events; 3) the response to an abrupt increase in CO2 is generally stronger compared to a more gradual one.