bluuebunny/crossref_metadata_2025 huggingface dataset:
Orientation of broadband seismographs in the Kashmir Himalaya: Effect on vector-based studies
Authors: Mir Ramees , Parvez Imtiyaz , Gaur Vinod
Published: March 2021

We used regional as well as global Rayleigh wave signals (source-receiver distance: 5°-175°; M≥ 6, Depth ≤ 150 km) recorded at 12 broadband seismic stations in northwestern Himalaya to compute arrival angles of surface waves at each station, assuming orthogonality of the horizontal components, and error-free levelling of the instrument. The average of all measurements at a station with cross-correlation values > 0.8, between Hilbert transformed vertical and radial components, was interpreted as the degree of misalignment of the horizontal components in a geographic frame of reference.

Out of the 12 station data used in this analysis, 3 were found to have instrument misorientation errors between 5° and 10° w.r.t geographic north, 2 between 10° and 15° and the remaining 7 < 5°. The number of measurements at each of these stations ranged from 75 to 331, with 11 stations having more than 90 measurements, assuring high reliability. We also analysed data from two nearby broadband instruments located in Ladakh Himalaya. One of these (LEH) with 46 measurements showed a misorientation error of 14.87°±4.87° and the other (HNL) with 48 showed an error of 0.75°±3.48°. Since misorientation errors based on less than 90 data elements are considered to be unstable, these were not used for further analysis.

We evaluated the effect of seismograph misorientations on the inverted solutions for P-wave receiver functions (RFs) and core-refracted shear waves (SKS). The errors in Moho depths and those of other intra-crustal features were within ±2 km for instrument misorientations of up to ~15°, that is close to the resolution errors. But, the SKS results, notably the azimuths of the fast component, were, found to be quite sensitive to instrument misalignment. For example, a ~14° error in orientation was found to cause a shift of up to 20° in the calculated azimuth of the fast component. Corrections of misorientation errors in both cases showed reduction of variance in the inverted solutions.
Analysis of agronomic drought over North Africa using remote sensing satellite data
Authors: Zribi Mehrez , Nativel Simon , Le Page Michel
Published: March 2021

This paper aims to analyze the agronomic drought in a highly anthropogenic  semi-arid region, North Africa. In the context of the Mediterranean climate, characterized by frequent droughts, North Africa is particularly affected. Indeed, in addition to this climatic aspect, it is one of the areas most affected by water scarcity in the world. Thus, understanding and describing agronomic drought is essential. The proposed study is based on remote sensing data from TERRA-MODIS and ASCAT satellite, describing the dynamics of vegetation cover and soil water content through NDVI and SWI indices. Two indices are analyzed, the Vegetation Anomaly Index (VAI) and the Moisture Anomaly Index (MAI). The dynamics of the VAI is analyzed for different types of regions (agircultural, forest areas). The contribution of vegetation cover is combined with the effect of soil water content through a new drought index combining the VAI and MAI. A discussion of this combination is proposed on different study areas in the study region. It illustrates the complementarity of these two informations in analysis of agronomic drought.
Comparative analysis of three NDVI resolutions in different urban typologies. The case of Granollers in the Metropolitan Area of Barcelona.
Authors: García-Haro Alan , Roca Josep
Published: March 2021

In recent years, the use of remote sensed NDVI has become recurrent in urban studies regarding the adaptation of cities to climate change. However, due to the physical diversity within cities and the different resolution offered by the sensors, the territorial interpretation of what the NDVI values really mean becomes difficult. Where the larger the size of the cells of the image, the greater the number of elements of the built environment within it, and the more complex the interpretation becomes.

In this work, the relationship between the NDVI of three sensors with different cell resolution for the same location and date is studied. In particular, the city of Granollers in the Metropolitan Area of Barcelona is analyzed. First, the NDVI images were obtained from Landsat-8 with 30m resolution, Sentinel-2 with 10m and from the Ministry of Agriculture, Livestock, Fisheries and Food of Catalonia (DARP) with 0.125m resolution. Then, the comparison was performed with a sample of five different typologies of the territory: dense urban core, suburban, industrial, area of highway and rural.

As first results, a supervised classification of the DARP image allowed the definition of 0.30 as the precise minimum value of NDVI that indicates the actual presence of vegetation. On the other hand, the comparison indicates that, in the urban context, the larger the cell size, the presence of vegetation quality is overestimated, where the higher percentage of cells is concentrated in higher NDVI values than in those with lower resolution. However, this behavior is not appreciated in rural areas, where higher percentages of cells of different resolutions were concentrated in the same NDVI ranges.

In such a way, it is corroborated that it is in the urban context where this indicator has a greater difficulty of territorial interpretation. Statements that are analyzed in greater depth in this study, where its implications in the use of NDVI in urban studies for the adaptation of cities to climate change are discussed.
A comparative literature review of the methodologies to evaluate risk of NaTech disasters and Critical Infrastructure affected by natural hazard
Authors: D'Ayala Margherita , Giusti Riccardo , Arosio Marcello , Martina Mario
Published: March 2021

In a climate change framework extreme natural events are going to occur more frequently and intensively as a result of global warming. Therefore, the effects and consequences of climate-related natural hazards, such as flooding, heatwaves, drought, landslides and others, have the potential to become more disastrous and extensive. Consequences of such events are of particular concern considering that today’s societies are interconnected in complex and dynamic socio-technological networks and, hence, dependent more than before on Critical Infrastructures (CI) systems (such as transport, energy, water, ICT systems, etc.). Furthermore, there are also events of Natural Hazards Trigger Technological Disasters (also known as NaTech events), whereby an industrial accident caused by a natural event could affect people, the environment, and other facilities and systems. This work reviews studies in the fields of risk assessment of CI systems affected by natural hazards and NaTech events.

This study identifies and classifies: the methodologies applied (qualitative or quantitative), the type of infrastructures exposed (transport, electricity, oil, gas, water and waste water and telecommunications systems, industrial or nuclear plant) and hazard considered (flood, earthquake, lighting, landslide, avalanche, storm surge, heat and cold waves, wind), the scale of application and the level of spatial resolution.

The work provides a comparison of the scientific studies, the objectives and analysis methods to assess risk employed in the fields of CI systems and NaTech events in order to highlight similarities and differences and to guide the most suitable approach for each application case.
First results from combined EUI and SPICE observations of Lyman lines of Hydrogen and He II
Authors: Teriaca Luca ,   EUI and SPICE Teams
Published: March 2021

The Solar Orbiter spacecraft carries a powerful set of remote sensing instruments that allow studying the solar atmosphere with unprecedented diagnostic capabilities. Many such diagnostics require the simultaneous usage of more than one instrument. One example of that is the capability, for the first time, to obtain (near) simultaneous spatially resolved observations of the emission from the first three lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact, the SPectral Imaging of the Coronal Environment (SPICE) spectrometer can observe the Lyman beta and gamma lines in its long wavelength (SPICE-LW) channel, the High Resolution Lyman Alpha (HRILYA) telescope of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take images dominated by the Lyman alpha line of ionized Helium at 30.4 nm (FSI-304). Being hydrogen and helium the main components of our star, these very bright transitions play an important role in the energy budget of the outer atmosphere via radiative losses and the measurement of their profiles and radiance ratios is a fundamental constraint to any comprehensive modelization effort of the upper solar chromosphere and transition region. Additionally, monitoring their average ratios can serve as a check out for the relative radiometric performance of the two instruments throughout the mission.

Although the engineering data acquired so far are far from ideal in terms of time simultaneity (often only within about 1 h) and line coverage (often only Lyman beta was acquired by SPICE and not always near simultaneous images from all three telescopes are available) the analysis we present here still offers a great opportunity to have a first look at the potential of this diagnostic from the two instruments.

In fact, we have identified a series of datasets obtained at disk center and at various positions at the solar limb that allow studying the Lyman alpha to beta radiance ratio and their relation to He II 30.4 as a function of the position on the Sun (disk center versus limb and quiet Sun versus coronal holes).
Subpollen particles (SPP) of birch as carriers of ice nucleating macromolecules
Authors: Burkart Julia , Gratzl Jürgen , Seifried Teresa , Bieber Paul , Grothe Hinrich
Published: March 2021

Wind pollinated trees such as birch trees release large amounts of pollen to the atmosphere during their blooming season in early spring. Due to the large size of pollen (birch pollen diameter: 20-25 µm) and short residence time in the atmosphere, their impact on cloud formation was believed to be negligible. However, in recent years studies have shown that ice nucleating materials, so called ice nucleating macromolecules (INM), much smaller in size can be extracted from pollen. At the same time there is evidence from medical studies that pollen can rupture under conditions of high humidity in the atmosphere and expel cytoplasmic material including starch granules, commonly referred to as subpollen particles (SPP). INM or SPP are much smaller and potentially more numerous than pollen and could significantly affect cloud formation in the atmosphere.

In this study, we focus on birch pollen and investigate the relationship between pollen grains, INM and SPP. According to the usage of the term SPP in the medical field we define SPP as the starch granules contained in pollen grains. We develop an extraction method to generate large quantities of SPP and investigate their ice nucleation activity. To our knowledge, this is the first study to investigate the ice nucleation activity of isolated SPP. We show that INM are only loosely attached to SPP and that purified SPP are not ice nucleation active: after several times of washing SPP with ultrapure water the ice nucleation activity completely disappears. In addition, we study the chemical nature of the INM with fluorescence spectroscopy and quantify the protein concentration with the Bradford assay. Fluorescence excitation-emission maps indicate a strong signal in the protein range (maximum around λex = 280 nm and λem = 330 nm) that correlates with the ice nucleation activity. In contrast, with purified SPP this signal is lost. The protein concentration ranges from 77.4 μg mL-1 for highly concentrated INM to below 2.5 μg mL-1 for purified SPP. The results thereby indicate a linkage between ice nucleation activity and protein concentration. Purified SPP are not ice nucleation active but could, however, act as carriers of INM and distribute those in the atmosphere.
Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept, results and outlook
Authors: Petäjä Tuukka ,   iCUPE team
Published: March 2021

The world is changing. The polar regions are critical component in the Earth system and influenced by on-going megatrends, such as globalization and demographical changes. The extensive use of Arctic natural resources will have effects on regional pollutant concentrations in the Arctic. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with a polar focus. We deploy an integrated approach with in-situ observations, satellite remote sensing and multi-scale modeling to synthesize data from a suite of comprehensive long-term measurements, intensive campaigns, and satellites. This enabled us to deliver novel data and indicators descriptive of the polar environment. The iCUPE framework includes thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation data streams. Here we summarize the project results and provide novel insights into continuation of the work. 
Recurrence based coupling analysis between event-like data and continuous data
Authors: Banerjee Abhirup , Goswami Bedartha , Marwan Norbert , Merz Bruno , Kurths Juergen
Published: March 2021

Extreme events such as earthquakes, tsunamis, heat weaves, droughts, floods, heavy precipitation, or tornados -- affect the human communities and cause tremendous loss of property and wealth, but can be related to multiple and complex sources. For example, a flood is a natural event caused by many drivers such as extreme precipitation, soil moisture, or temperature. We are interested in understanding the direct and indirect coupling between flood events with different climatological and hydrological drivers such as soil moisture and temperature.

We use multivariate recurrence plot and recurrence quantification analysis as a powerful framework to study the couplings between the different systems, especially the direction of coupling. The standard delay-embedding method is not a suitable for the recurrence analysis of event-like data. Therefore, we apply the novel edit-distance method to compute recurrence plots of time series of flood events and use the standard recurrence plot method for the continuous varying time series such as soil moisture and temperature. The coupling analysis is performed using the mean conditional probabilities of recurrence derived from the different recurrence plots. We demonstrate this approach on a prototype system and apply it on the hydrological data. Using this approach we are able to indicate the coupling direction and lag between the different coupled systems.
Analysis of diurnal cycles of interferometric coherence and backscattering coefficient measured on an irrigated wheat field in Morocco
Authors: Ouaadi Nadia , Villard Ludovic , Ezzahar Jamal , Frison Pierre-louis , Khabba Saïd , Chakir Adnane , Er-raki Salah , Jarlan Lionel
Published: March 2021

C-band radar observations have shown a high sensitivity to the water status of vegetation, including forests and crops. Several studies conducted mainly on forests have observed daily changes of the backscattering coefficients between ascending and descending orbits and have suggested that these differences are related to the diurnal cycle of vegetation water content. Likewise, the water movement within annual crops could be associated to change of the phase centre locations leading to a daily cycle of the interferometric coherence as well that has already been observed on tropical forest using C-band in situ acquisitions. In this context, an experimental setup composed of 4C-band antennas targeting an irrigated wheat field was installed at the top of a 20 m tower near Chichaoua (Morocco) from January to June 2020. The collected data includes measurements of the backscattering coefficient at both cross- and parallel polarizations and the interferometric coherence with a 15 mns time step. The field is also equipped with an eddy-correlation station for half hourly measurements of convective fluxes, soil moisture and temperature profiles. Simultaneously, measurement of above-ground biomass, leaf area index, canopy height and surface roughness are also carried out every 15-daysduring the agricultural season.  The preliminary results of the experiment reveal the existence of strong correlation between the daily evolution of interferometric coherence and the physiological activity of wheat at dawn while the changes observed in the afternoon are ratherrelated to the wind peaks. For the backscattering coefficient, a good agreement is observed between the evolution of its daily average and the evolution of evapotranspiration. These open insights for the monitoring of the crops water status using radar dataacquired at sub-daily timescale.
Ensemble strategies for Flash Flood Forecasting: the 29 October 2018 event in the Eastern Italian Alps
Authors: Pérez Ciria Teresa , Zaramella Mattia , Dallan Eleonora , Giovannini Lorenzo , Zardi Dino , Davolio Silvio , Borga Marco
Published: March 2021

On 27-29 October 2018, heavy precipitation over the Eastern Italian Alps (the so-called “Vaia Storm”) led to an extreme flood, causing several casualties and extensive damages to buildings and infrastructures. The event, which occurred at the end of a climatic anomaly of prolonged drought, developed into two phases: a first phase (October 27-28) and a short, but more intense second phase on the 29th. The event was characterized by extreme accumulated precipitation, and several flash floods in the second phase. A previous work focused on the implementation of two NWP models (MOLOCH and WRF) at convection permitting resolution and showed a general good predictability of the precipitation event, associated with a well-defined large-scale forcing. This work aims at providing an outline of the hydrological predictability, focusing on different river systems in the area (the Upper Adige, the Piave and the Bacchiglione-Astico river systems), with different characteristics in terms of drainage areas, elevations and positions within the region hit by the event. For this, the hydro-meteorological forecasting chain includes the two mesoscale models (MOLOCH and WRF), driven by two global analysis systems (GFS-NCEP and IFS-ECMWF), and a grid-based spatially distributed hydrologic model termed GRIS (Grid-based runoff simulation model). We examine different ensemble strategies for the initialization of the hydro-meteorological chain and focus on the assessment of hydrological predictability, paying specific attention to basins with high regulation capacity thanks to the presence of hydropower storage.
Didymos Gravity Science Investigations through Ground-based and Inter-Satellite Links Doppler Tracking
Authors: Tortora Paolo , Zannoni Marco , Gramigna Edoardo , Lasagni Manghi Riccardo , Le Maistre Sebastien , Park Ryan S. , Tommei Giacomo , Karatekin Ozgur , Goldberg Hannah , Martino Paolo , Concari Paolo , Kueppers Michael , Michel Patrick , Carnelli Ian
Published: March 2021

The Asteroid Impact and Deflection Assessment (AIDA) is an international collaboration supported by ESA and NASA to assess the feasibility of the kinetic impactor technique to deflect an asteroid, combining data obtained from NASA’s DART and ESA’s Hera missions. Together the missions represent the first humankind’s investigations of a planetary defense technique. In 2022, DART will impact Dimorphos, the secondary of the binary near-Earth asteroid (65803) Didymos.  After 4 years, Hera will follow-up with a detailed post-impact survey of Didymos, to fully characterize and validate this planetary defense technique. In addition, Hera will deploy two CubeSats around Didymos once the Early Characterization Phase has completed, to augment the observations of the mother spacecraft. Juventas, the first Cubesat, will complete a low-frequency radar survey of the secondary, to unveil its interior. Milani, the second Cubesat, will perform a global mapping of Didymos and Dimorphos, with a focus on their compositional difference and their surface properties. One of the main objectives of Hera is to determine the binary system’s mass, gravity field, and dynamical state using radio tracking data in combination with imaging data. The gravity science experiment includes classical ground-based radiometric measurements between Hera and ground stations on Earth by means of a standard two-way X-band link, onboard images of Didymos, and spacecraft-to-spacecraft inter-satellite (ISL) radiometric tracking between Hera and the Cubesats. The satellite-to-satellite link is a crucial add-on to the gravity estimation of low-gravity bodies by exploiting the Cubesats’ proximity to the binary, as the range-rate measurements carried out by the inter-satellite link contain information on the dynamics of the system, i.e., masses and gravity field of Didymos primary and secondary.

We will describe the updated mission scenario for the Hera radio science experiment to be jointly carried out by the three mission elements, i.e., Hera, Juventas and Milani. To conclude, our updated analysis and latest results, as well as the achievable accuracy for the estimation of the mass and gravity field of Didymos and Dimorphos, are presented.
IBISAR downstream service: one year of supporting emergency response at sea
Authors: Reyes Reyes Emma
Published: March 2021

IBISAR is a user-friendly science-based data downstream service that allows to visualize, compare and evaluate the performance of ocean current predictions in the Iberian-Biscay-Irish (IBI) regional seas. It is designed for emergency responders and Search and Rescue (SAR) operators, to facilitate decision-making by guiding users to identify the most accurate current prediction in near-real time. 

IBISAR service portfolio includes ocean surface current predictions from models, as well as the surface current observations from all the High-Frequency radars and satellite-tracked drifters available in the IBI region from the Copernicus Marine Environment Monitoring Service (CMEMS) portfolio. It also includes coastal and regional models from complementary databases.

The service is freely accessible under registration and offers a visualization interface to make data inter-comparison, and the skill assessment tool for evaluating the accuracy of the different predictions available in a specific area and period of interest, as defined by the user. IBISAR evaluates the performance of available models and HF radars by comparing them versus drifter trajectories based on a Lagrangian approach, providing a skill score easily interpretable to end-users. The validation of the skill assessment methodology envisaged by the IBISAR service has been applied and tested in 4 different pilot areas of the IBI region against more than 140 drifters.

Finally, it is worth mentioning that IBISAR service is the result of a CMEMS User Uptake project, which together with the CMEMS Service Evolution INCREASE project, complement operational activities and feed the upstream and downstream development of the CMEMS service in the coastal zones.
Evaluation of the regional reanalysis COSMO-REA6 vs ERA-Interim for improving the dealiasing analysis of GRACE/GRACE-FO mission data
Authors: Dixit Shashi , Friederichs Petra , Hense Andreas
Published: March 2021

This work is part of the Research Group New Refined Observations of Climate Change from Spaceborne Gravity Missions (NEROGRAV), which is funded by the German Research Foundation (DFG). The goal of NEROGRAV is to develop new analysis methods and modeling approaches to improve the resolution, accuracy, and long-term consistency of mass transport series from the GRACE and GRACE-FO missions. This can only be obtained by improving the sensor data, background models, and processing strategies for satellite gravimetry. Within NEROGRAV, the joint Geodesy and Meteorology group at the University of Bonn is responsible for the investigation of the atmospheric and hydrological effects on the dealiasing of GRACE/GRACE-FO observations of the Earth’s gravity field.

In the present study we compare 3-hourly data from the ERA-Interim realanysis with a grid size of 50 km based on a hydrostatic model of the atmosphere and the houly data of the non-hydrostatic COSMO reanalysis with a grid size of 6 km (COSMO-REA6, Bollmeyer et.al (2015), QJRMS, 141(686), 1-15.). To date, atmospheric mass variability has been studied largely through data from hydrostatic models of the atmosphere. Therefore a direct evaluation of the total atmospheric mass variability including non-hydrostatic effects compared to a hydrostatic background model is necessary. Further, GRACE/GRACE-FO is expected to be sensitive to the atmospheric water mass variability. Since a high resolution atmospheric model provides an intensified water cycle, a more localised and enhanced mass variability within all water components is expected in COSMO-REA6.

The objectives of this talk are to (1) present the evaluation results of non-hydrostatic effects and water mass transports on the atmospheric mass variability and (2) assess the scale effects of a coarse vs a fine resolution representation of the atmospheric mass. Both objectives place an emphasis on the contributions of the atmospheric hydrological cycle in two views: the systematic effects are investigated by the mean values, while spatial variability effects are investigated using a principal component analysis. The study concentrates on the summer season 2007 over the CORDEX (North Atlantic, European region) domain.
Hydrodynamics of wave-current interaction at a right angle over rough beds
Authors: Marino Massimiliano , Faraci Carla , Musumeci Rosaria Ester
Published: March 2021

In the present work, an investigation on the hydrodynamics of waves and currents interacting at right angle over rough beds has been carried out. The work focuses on the effects of wave motion superposed on the current steady boundary layer, and on how the oscillatory flow affects the current velocity distribution, in the presence of gravel and sand beds.

A laboratory experimental campaign on wave-current orthogonal interaction has been carried out in a shallow water basin at DHI Water and Environment (Hørsholm, Denmark).

Mean flow has been investigated by computing time- and space-averaged velocity profiles. Friction velocity and equivalent roughness have been inferred from the velocity profiles by best fit technique, in order to measure the shear stress experienced by the current mean flow.

Tests in the presence of only current, only waves and combined flow have been performed.

Instantaneous velocities have been Reynolds-averaged to obtain turbulent fluctuations time series and compute turbulence related quantities, such as turbulence intensities and Reynolds stresses.

The analysis of the mean flow revealed a complex interaction of the waves and currents combined flow. Depending on the relative strength of the current with respect to the waves, the superposition of the oscillatory flow may determine an increase or a decrease of the bottom friction experienced by the current.

The superposition of waves always induces an increase of turbulence intensity, except over gravel bed in which a decrease is observed in the very proximity of the bottom. Over gravel bed, the presence of the oscillatory flow determines a decrease of the turbulent intensity gradient, which may be related to the decrease of bottom friction observed in the mean flow analysis.

A turbulence quadrant analysis has been performed and showed that, in the presence of a lone current over a flat gravel bed, the turbulent ejection-sweep mechanism reaches parts of the water column closer to the water surface, similar to what has been observed in the turbulence intensity profiles.

The superposition of the oscillatory flow appears to induce an increment of ejections and sweeps intensity, which is associated with the shear stress increase at the bottom observed in the mean flow analysis. Moreover, a decrease of the number of ejection and sweep events has been recorded, which suggests a suppression of the ejection-sweep events alongside an enhancement of their intensity.
The Thores volcanic island arc of the Pearya Terrane from Ellesmere Island formed on Precambrian continental crust
Authors: Majka Jarosław , Kośmińska Karolina , Bazarnik Jakub , McClelland William C.
Published: March 2021

We report on U-Pb zircon dating and bulk rock geochemistry results of intermediate to felsic rocks of the Thores Suite of the Pearya Terrane, northern Ellesmere Island (Arctic Canada).  Our new results together with the previously published data show that the Thores Suite was formed in the Early Ordovician (c. 490-470 Ma) as a part of an island arc. Some of the dated samples revealed common xenocrystic zircon. The latter yielded ages ranging between c. 2690 Ma and c. 520 Ma. The obtained ages of xenocrystic zircon are interpreted to be typical of Laurentia. We propose that the youngest obtained cluster of ages c. 580-570 Ma expresses a component typical for the Timanide Orogen, which is conventionally tied to Baltica. The newdataset sheds light on the history and understanding of the Thores Suite, which used to be explained as an effect of the M’Clintock orogenesis. The latter event was commonly presented as foreign to the major Caledonian orogenesis sensu stricto. In our view, the Thores Suite represents an island arc, which was formed on a fragment of continental crust dismembered during Iapetus opening. Importantly, the age of the Thores island arc is coeval with other island arcs and high pressure metamorphic units of the Scandinavian and Svalbard Caledonides. Thus, it is likely that the Thores volcanic island arc was a part of the larger arc system operating within northern Iapetus. The juxtaposition of the Thores arc with the other successions of the Pearya Terrane is ascribed to a major sinistral strike-slip escape fault-system developed along the northeastern margins of Baltica and Laurentia, broadly concurrent with the main Scandian collision between the two aforementioned continents. This crustal scale fault structure enabled the juxtaposition of numerous crustal blocks of different Precambrian ancestry that can be found in various regions of the current High Arctic, including Svalbard, Greenland and Ellesmere Island.

This research was supported by the National Science Centre (Poland) project no. 2015/17B/ST10/03114 and the internal AGH-UST funding to J. Majka, the internal grant of the Polish Geological Institute - NRI no. 62.9012.2014.00.0 to J. Bazarnik and the National Science Foundation (USA) grant EAR1650022 to J. Gilotti and W. McClelland.
Molecular dynamics simulations of homogeneous CO2 nucleation
Authors: Tikkanen Valtteri , Dingilian Kayane , Halonen Roope , Reischl Bernhard , Wyslouzil Barbara , Vehkamäki Hanna
Published: March 2021

The condensation of carbon dioxide (CO2) is a topic of general interest in view of global decarbonization targets, e.g. in low-temperature CO2 capture technologies promoting the phase transition of CO2 gas is the crucial step. Homogeneous nucleation of a mixture of CO2 and argon gas in a supersonic nozzle has been studied at temperatures from 78 to 92 K, and CO2 partial pressures between 70 and 800 Pa. The consistency between the current data and measurements at higher temperature suggests the critical clusters remain liquid-like even at these low temperatures.

Here we present large-scale atomistic molecular dynamics (MD) simulations of homogenous CO2 nucleation from the vapour phase at temperatures from 75 to 105 K. The MD approach is an unbiased method to study the nucleation process, including the phase and structure of even the smallest clusters. We used argon carrier gas as a heat bath for the CO2 molecules to avoid unphysical removal of latent heat.

Simulations confirm that despite strong undercooling, nucleation proceeds through liquid-like clusters. Also, by applying standard steady-state cluster growth kinetics, we are able to calculate the cluster formation free energies from the MD simulations. The results suggest a curvature correction to the classical liquid drop model used in the classical nucleation theory. The correction depends only on the bulk liquid properties, and hence the simulation-based correction can be applied to predict the nucleation rates of real CO2.

The simulation-based theory is able to capture the magnitude and the temperature-dependency of the nucleation rate rather well, whereas both standard CNT and its self-consistent version (SCNT) underestimate the rate by several orders of magnitude. Here we have corrected the theoretical values with the non-isothermal factor, which is about 0.01-0.1 for the studied system.
Lake ice phenology changes in the northern hemisphere
Authors: Qiu Yubao , Wang Xingxing , Leppäranta Matti , Cheng Bin , Zhang Yixiao
Published: March 2021

Lake-ice phenology is an essential indicator of climate change impact for different regions (Livingstone, 1997; Duguay, 2010), which helps understand the regional characters of synchrony and asynchrony. The observation of lake ice phenology includes ground observation and remote sensing inversion. Although some lakes have been observed for hundreds of years, due to the limitations of the observation station and the experience of the observers, ground observations cannot obtain the lake ice phenology of the entire lake. Remote sensing has been used for the past 40 years, in particular, has provided data covering the high mountain and high latitude regions, where the environment is harsh and ground observations are lacking. Remote sensing also provides a unified data source and monitoring standard, and the possibility of monitoring changes in lake ice in different regions and making comparisons between them. The existing remote sensing retrieval products mainly cover North America and Europe, and data for Eurasia is lacking (Crétaux et al., 2020).

Based on the passive microwave, the lake ice phenology of 522 lakes in the northern hemisphere during 1978-2020 was obtained, including Freeze-Up Start (FUS), Freeze-Up End (FUE), Break-Up Start (BUS), Break-Up End (BUE), and Ice Cover Duration (ICD). The ICD is the duration from the FUS to the BUE, which can directly reflect the ice cover condition. At latitudes north of 60°N, the average of ICD is approximately 8-9 months in North America and 5-6 months in Eurasia. Limited by the spatial resolution of the passive microwave, lake ice monitoring is mainly in Northern Europe. Therefore, the average of ICD over Eurasia is shorter, while the ICD is more than 6 months for most lakes in Russia. After 2000, the ICD has shown a shrinking trend, except northeastern North America (southeast of the Hudson Bay) and the northern Tibetan Plateau. The reasons for the extension of ice cover duration need to be analyzed with parameters, such as temperature, the lake area, and lake depth, in the two regions.
Near real time high resolution mapping of flood extent in west African sites
Authors: Cherif Ines , Ovakoglou Georgios , Alexandridis Thomas K. , Mensah Foster , Garba Issa
Published: March 2021

Flood disasters cause severe damages to African communities (destroyed infrastructure, submerged fields, loss of life) and have an increasing occurrence under the changing climate. The spatial and temporal resolutions of the Sentinel-1 radar data are favourable assets towards improving the capacity to monitor flood events. Flood mapping is included among the services developed within the AfriCultuReS project, with the overall aim to improve food security in Africa (http://africultures.eu/). The widely used SAR threshold imaging technique for the automatic mapping of flood extent from Sentinel-1 images was tested in two pilot sites of the project, in Ghana and Niger. Two flood events with different characteristics were considered: the spillage of the Bagre dam in the south of Burkina Faso which caused farmlands to flood in north-east Ghana in August 2018 and the flood of the Niger river around Niamey after torrential rain in August 2017. These two case studies in west Africa allowed the assessment of the robustness of the method to provide timely flood delineation maps to end users and potential stakeholders. The results were evaluated through expert opinion and comparison to available reference data such as maps from the Copernicus Management Service (CEMS) which was activated in the case of the riverine flood in Niger (Copernicus EMSR235). The results show that the approach can be applied for a rapid and near-real time mapping of the flood extent in the pilot sites of the project AfriCultuReS. The near real time maps can lead to a faster assessment of the flood event severity and its damages on the local communities, help initial reporting to national institutions, and feed existing flood databases such as MifMASS for west Africa. Based on this approach a flood mapping service is under development as part of the AfriCultuReS Disasters Mapping and Monitoring service (AfriCRS-S4-P03).
24 years of C3S Arctic regional reanalysis
Authors: Nielsen Kristian Pagh , Schyberg Harald , Yang Xiaohua , Støylen Eivind , Dahlgren Per , Amstrup Bjarne , Peralta Carlos , Køltzow Morten , Bojarova Jelena
Published: March 2021

The Copernicus Climate Change Service (C3S) regional reanalysis for the Arctic consists of two datasets of Essential Climate Variables (ECVs) for the 24 year period from 1997 to 2021. The high resolution (2.5x2.5 km2) datasets cover Greenland, Iceland, Svalbard, the Barents Sea and Northern Scandinavia. Several islands in the Russian Arctic and a few islands in the Canadian Arctic are also covered. The produced datasets are freely available to all. A first subset of the data has been published on the Copernicus Data Store (CDS) in early 2021.

The reanalysis is perfomed with state-of-the-art data assimilation techniques that include many local quality-controlled observations that have not been included in previously published reanalysis datasets. The weather forecasting model HARMONIE-AROME cy40h1.1.1 has been used to produce the dataset. The model computations have additionally been optimized for processes essential in the Arctic. Estimated uncertainty data have been produced at atmospheric pressure levels, and validation statistics have been made for synoptic weather stations.
A precipitation phase discriminator for IMPROVER
Authors: Moseley Stephen
Published: March 2021

Knowledge of the expected precipitation phase is crucial for mitigating the impacts snow and ice on national infrastructure. This is sensitive to the altitude of the modelled forecast grid point which varies between models.

The IMPROVER project aims to blend probabilistic model variables from different models. This presentation describes the approach used to standardise the phase change levels of falling precipitation from the Met Office UK and Global models over the high-resolution UK domain.

The method uses wet-bulb temperature profiles to identify the surface where snow changes to sleet and sleet changes to rain, interpolates these surfaces through model orography and below sea level, then extracts the predicted phase at the altitude of the standard high-resolution UK orography. This is performed for each model realization to maintain the multivariate connection between precipitation and precipitation phase.

The precipitation phase discriminators are used to categorise precipitation rate and accumulation probability data into rain, sleet and snow phases which in turn inform a categorical most-likely weather code.

We present results from a one-month trial using data from February 2020 comparing the weather code forecasts with site observations across the UK.
The response of the ozone layer under abrupt 4xCO2 in CMIP6
Authors: Chiodo Gabriel , Ball William T. , Nowack Peer , Orbe Clara , Keeble James , Diallo Moha , Hassler Birgit
Published: March 2021

Previous studies indicate a possible role of stratospheric ozone chemistry feedbacks in the climate response to 4xCO2, either via a reduction in equilibrium climate sensitivity (ECS) or via changes in the tropospheric circulation (Nowack et al., 2015; Chiodo and Polvani, 2017). However, these effects are subject to uncertainty. Part of the uncertainty may stem from the dependency of the feedback on the pattern of the ozone response, as the radiative efficiency of ozone largely depends on its vertical distribution (Lacis et al., 1990). Here, an analysis is presented of the ozone layer response to 4xCO2 in chemistry–climate models (CCMs) which participated to CMIP inter-comparisons. In a previous study using CMIP5 models, it has been shown that under 4xCO2, ozone decreases in the tropical lower stratosphere, and increases over the high latitudes and throughout the upper stratosphere (Chiodo et al., 2018). It was also found that a substantial portion of the spread in the tropical column ozone is tied to inter-model spread in tropical upwelling, which is in turn tied to ECS. Here, we revisit this connection using 4xCO2 data from CMIP6, thereby exploiting the larger number of CCMs available than in CMIP5. In addition, we explore the linearity of the ozone response, by complementing the analysis with simulations using lower CO2 forcing levels (2xCO2). We show that the pattern of the ozone response is similar to CMIP5. In some models (e.g. WACCM), we find larger ozone responses in CMIP6 than in CMIP5, partly because of the larger ECS and thus larger upwelling response in the tropical pipe. In this presentation, we will discuss the relationship between radiative forcing, transport and ozone, as well as further implications for CMIP6 models.
Suppression of Baroclinic Eddies by Strong Jets
Authors: Hadas Or , Kaspi Yohai
Published: March 2021

The midlatitude storm tracks are one of the most prominent features of extratropical climate. Despite the theoretical expectation, based on baroclinic instability theory that baroclinic eddy strength correlates with jet intensity, there is a decrease in storm-track activity during midwinter over the Pacific compared to the shoulder seasons. Recent studies suggest this phenomenon is a result of the general circulation effect on the storm-track through interaction with the jet-stream. To isolate the effect of jet strength, we conduct a series of GCM experiments with a systematically varied jet intensity. The simulations are analyzed using Lagrangian tracking to understand the response from a single eddy perspective. The results of the Lagrangian analysis show that while the response of upper-level eddies is dominated by a reduction in the amount of tracked features, the lower-level eddies' response is also affected by a reduction in their lifetime. Analyzing the effect of the jet strength on the pairing between the upper- and lower-level eddies, we show how the jet intensification break the baroclinic wave structure and limits its growth. Furthermore, we show that these results can be settled with linear baroclinic instability models if the eddies' spatial scale is considered. The intensification of the jet and increase in the deformation radius shift the preferred scale for growth from the synoptic-scale toward the planetary-scale, consistent with the reduction in storm activity. This mechanism potentially explains the midwinter suppression of storm activity over the Pacific and the difference from the response over the Atlantic.
Developing Efficient Web Crawler for Effective Disaster Management
Authors: S Gopal Lakshmi , Prabha Rekha , Pullarkatt Divya , Vinodini Ramesh Maneesha
Published: March 2021

The exponential escalation of disaster loss in our country has led to the awareness that disaster risks are presumably increasing. In the past few years, numerous hazards have been reported in India which has caused severe casualties, infrastructural, agricultural and economic damages. Over the years, researchers have scrutinized social media data for disaster management as it has the advantage of being available in real time and stays relevant in hazard response. But, the authenticity of social media data has been questioned particularly in a disaster management scenario where false information cannot be afforded. Collection of credible disaster statistics during or after a hazard occurrence is a demanding task. Web documents such as a news report are credible when compared to social media data and hence, the proposed work aims in developing a web crawler which is a software that's capable of indexing legitimate news websites from the world wide web which contains news articles related to hazards. The articles are extracted by incorporating the technique of data scraping which includes the use of a developed hazard ontology. The ontology contains hazard relevant keywords at multiple granularities. The developed crawler is able to prioritise websites based on its contents which makes the data collection more accurate. The collected data is  analyzed and structured as it may assist in administering hazard emergencies during a hazard, preparedness before a hazard occurrence and other post disaster activities efficiently. The proposed work also focuses on local media as it may provide news reports from regional locations which might not be reported in the mainstream media.  News articles are written in natural languages and hence structuring them into a statistical form involves natural language processing methodologies. The proposed work mainly focuses on semantic information extraction from news articles to extract statistical data related to the hazard, its impacts and loss.  News illustrations often include less newsworthy content such as advertisements and past studies of the hazard location. Hence, a supervised learning based text classification is performed to classify newsworthy content from the articles and approximately 70% accuracy has been achieved.