bluuebunny/crossref_metadata_2025 huggingface dataset:
TOMOREF operator as a tool to improve weather forecasts
Authors: Hanna Natalia , Trzcina Estera , Kryza Maciej , Rohm Witold
Published: March 2021

The numerical weather model starts from the initial state of the Earth's atmosphere in a given place and time. The initial state is created by blending the previous forecast runs (first-guess), together with observations from different platforms. The better the initial state, the better the forecast; hence, it is worthy to combine new observation types. The GNSS tomography technique, developed in recent years, provides a 3-D field of humidity in the troposphere. This technique shows positive results in the monitoring of severe weather events. However, to assimilate the tomographic outputs to the numerical weather model, the proper observation operator needs to be built.

This study demonstrates the TOMOREF operator dedicated to the assimilation of the GNSS tomography‐derived 3‐D fields of wet refractivity in a Weather Research and Forecasting (WRF) Data Assimilation (DA) system. The new tool has been tested based on wet refractivity fields derived during a very intense precipitation event. The results were validated using radiosonde observations, synoptic data, ERA5 reanalysis, and radar data. In the presented experiment, a positive impact of the GNSS tomography data assimilation on the forecast of relative humidity (RH) was noticed (an improvement of root‐mean‐square error up to 0.5%). Moreover, within 1 hour after assimilation, the GNSS data reduced the bias of precipitation up to 0.1 mm. Additionally, the assimilation of GNSS tomography data had more influence on the WRF model than the Zenith Total Delay (ZTD) observations, which confirms the potential of the GNSS tomography data for weather forecasting.
Polluted cloud lines in satellite snapshots and satellite climatologies
Authors: Toll Velle , Trofimov Heido , Rahu Jorma , Post Piia
Published: March 2021

It is challenging to separate the cause from effect in aerosol-cloud interactions. Anomalous cloud lines polluted by anthropogenic aerosols help distinguish the cause from effect as properties of polluted clouds can be directly compared to nearby unpolluted clouds’ properties. Pollution tracks in clouds induced by localised aerosol emissions (Toll et al. 2019, Nature, https://doi.org/10.1038/s41586-019-1423-9)  are visually detectable ship-track-like quasi-linear polluted cloud features in satellite snapshots. We detected similar anomalous polluted cloud lines in the long-term average satellite data, where cloud response to aerosol over a long time is recorded. Polluted cloud tracks are induced by various aerosol sources like oil refineries, smelters, coal-fired power plants, smaller industry towns, ships, and volcanoes. We detected polluted cloud tracks at spatial scales varying from tens of kilometres to thousands of kilometres (Trofimov et al. 2020; JGR Atmospheres, https://doi.org/10.1029/2020JD032575).  

 

Polluted cloud tracks detected in satellite snapshots are excellent for the process-level understanding of aerosol-cloud interactions. Polluted cloud tracks recorded in satellite climatologies are great for estimating the average cloud response to aerosols. MODIS snapshots of polluted cloud tracks show relatively weak cloud water response to aerosols at various spatial scales. High-resolution analysis of South-East Atlantic shipping corridor shows partial off-set of the Twomey effect by decreased cloud water. Cloud fraction sometimes increases in the polluted cloud tracks and sometimes decreases compared to the nearby unpolluted clouds. The temporal evolution of cloud responses in pollution tracks estimated from geostationary SEVIRI data and meteorological conditions favourable for pollution track occurrence is presented. We expect that the utilisation of these real-world laboratories of aerosol impacts on clouds helps to improve global climate models’ physical parameterisations.
Towards the CO2Image mission: performance studies using AVIRIS-NG
Authors: Wilzewski Jonas S. , Strandgren Johan , Baumgartner Andreas , Haschberger Peter , Köhler Claas , Krutz David , Paproth Carsten , Chapman John W. , Thompson David R. , Thorpe Andrew K. , Mayer Bernhard , Roiger Anke , Butz André
Published: March 2021

Monitoring of anthropogenic carbon dioxide (CO2) emission sources with air- and space-borne remote sensing instruments relies on high-spatial resolution measurements. Such observations can be achieved at the expense of decreasing the spectral resolution of the instrument, which in turn complicates CO2 retrieval techniques due to the reduced information content of the spectra.

In preparation for the CO2IMAGE mission (Δλ ~ 1.3 nm) – a compact satellite proposal currently in phase A at the German Aerospace Center (DLR) – we present here a dedicated study of CO2 monitoring capabilities with the airborne AVIRIS-NG sensor (Δλ ~ 5 nm). We conduct CO2 retrievals of several clear-sky AVIRIS-NG point source observations with the RemoTeC algorithm, based on the short-wave infrared absorption bands of CO2. Favorable state vector and spectral retrieval window configurations are identified that reduce correlations between the carbon dioxide and water vapor column concentrations and surface reflection properties. We also discuss the use of a posteriori correction methods to minimize biases in the retrieved CO2 fields and, finally, we carry out source rate estimates for these case studies.
Application of Machine Learning for Evaluation of GNSS Processing Protocols
Authors: Rhyner Severin , Jordan Denis , Salvini Dante , Dach Rolf
Published: March 2021

The Center for Orbit Determination in Europe (CODE) hosts one of the global analysis centers of the International GNSS Service (IGS). Each day, the data of about 250 GNSS stations are processed in a highly automated manner. The processing protocols contain many quality parameters related to station coordinates, satellite orbits, and satellite/receiver clock corrections.

In the context of a reprocessing campaign, 25 years of GNSS measurements are analysed within a short timeframe and therefore a huge number of processing protocols are generated. A manual inspection of all these protocols is highly time consuming. Machine learning (ML) represents a promising approach to provide a data driven and objective evaluation of these protocols. The main objective of a ML framework is to analyse a big number of independent quality parameters in order to automatically detect individual days with problems in the data analysis. Furthermore, we expect that ML could contribute to the detection of unexpected systematics in the solutions and has the potential to improve the GNSS analysis strategy.

As a first step, we have focused on one aspect of the processing protocols, namely the orbit misclosures (discontinuities at the end of the orbital arcs) at midnight. It is known that the orbit modelling of GNSS satellites is more difficult during eclipse seasons. In order to assess the capabilities of different machine learning algorithms for our purpose, we have evaluated the magnitude of the orbit misclosures and have tried to recover the information on whether the satellite was passing the earth shadow or not. State-of-the-art ML algorithms (Random Forest and Decision Tree) showed promising results of up to 80% success rate.
Characterisation of seismic events using time-reverse imaging 
Authors: Finger Claudia , Saenger Erik H.
Published: March 2021

In addition to stable and accurate hypocenters of seismic events, the characterisation of events is crucial for the investigation of seismicity in the context of geothermal reservoirs, CO2-sequestration and other geotechnical applications. Since the origin and nature of the seismicity in such cases is still under investigation, tools should rely on as few a priori assumptions about the sources as possible. Here, an approach is presented to determine the time-dependent moment tensor and origin time in addition to commonly derived hypocenter locations of seismic events using time-reverse imaging (TRI). The full six component moment tensor is derived and may be used to display for example focal mechanisms. The workflow consists of determining the location of potential sources, discriminating artificial and true source locations and obtaining the time-dependent moment tensors by recording the stress components at the derived source locations. Since TRI does not rely on the identification of seismic phases but on the simulation of the time-reversed wavefield through an adequate velocity model, no assumptions about the source location or the type of source mechanism is made. TRI is less affected by low signal-to-noise ratios and is thus promising for noisier sites and quasi-simultaneous events. However, a sufficient number of seismic stations are needed to accurately sample the wavefield spatially. The proposed workflow is demonstrated by locating and characterising microseismic events in the geothermal field of Los Humeros, Mexico. Although higher levels of noise are present and only a one-dimensional velocity model is available at this time, selected events could be located and characterised.
Long-term physiological and growth responses of oak trees under climate warming in eastern Asia
Authors: Arco Molina Julieta Gabriela , Treydte Kerstin , Maredova Nela , Saurer Matthias , Dolezal Jiri , Song Jong-Suk , Altman Jan
Published: March 2021

Climate changes and raising atmospheric CO2 concentrations are expected to influence tree and forest development. However, the direction and intensity of the tree and forest responses are diverse, and long-term studies are scarce.  Here, we studied responses of Quercus mongolica to climate over the last 117 years based on the tree-ring width, δ13C-derived physiological parameters (Δ13C, Ci and iWUE) and δ18O in Jeju Island, South Korea. Trend and change point analyses were performed to the radial tree growth, physiology and climate, and tree responses-climate relationships were analysed temporally and spatially. iWUE significantly increased since 1900 but decadal variations were observed in 1950, 1975 and 2010, revealing an evolving physiological response. iWUE was mainly driven by stimulated photosynthesis under no water limitations. This photosynthetic stimulation was driven mainly by the atmospheric CO2 fertilization, warming and higher radiation, probably through the simultaneous influence on the phenology and physiology of trees. At a local scale, higher radiation combined with less cloudy conditions were the factors with the greatest positive influence on tree growth, while at a regional scale land and sea surface temperatures positively influenced both tree growth and physiology. Moreover, all these responses strongly intensified after the 1970s, showing that tree responses are not temporary stable. Altogether, the present results indicated that the physiology and growth of Q. mongolica from eastern Asia are driven by a combination of climatic, ecological and anthropogenic factors. Moreover, the significant, rapid and unprecedented changes in the tree responses indicated that trees may benefit from recent global changes, showing a physiology-driven growth enhancement. This represents a key understanding of trees and forests ecosystems responses to future climate changes, which is relevant to assess and design global change mitigation strategies.
Permo-Triassic Oceanic and Adjacent Continental Lithosphere in the Eastern Mediterranean, from surface-wave and wide-angle imaging
Authors: El-Sharkawy Amr , Meier Thomas , Hübscher Christian , Lebedev Sergei , Dannowski Anke , Kopp Heidrun , Behrmann Jan H. , McGrandle Andrew , Hamada Mona
Published: March 2021

The Earth’s oldest oceanic lithosphere preserved in-situ is in the eastern Mediterranean Sea. It can offer essential information on the oceanic plate evolution. Yet, its thickness and other properties have been difficult to determine by means of seismic imaging due to the high heterogeneity of the region. Here, we combine a large, new surface wave dataset with published wide-angle data in order to map the properties and lateral variability of the oceanic lithosphere, as well as the ocean-continent transition in the easternmost Mediterranean beneath the Levant Basin. We use stochastic joint inversion of broad band, phase-velocity dispersion measurements and seismic refraction P-wave velocity models to obtain 1-D, shear wave velocity models down to 300 km depth and compare the structure beneath the Ionian Sea and the Levant Basin. The thickness of the crust is about 16.4 ± 3 km and 22.3 ± 2 km beneath the chosen locations within the Ionian Sea and the Levant Basin, respectively. The Poisson’s ratio of about 0.32 and Vp/Vs of about 1.93 in the crystalline crust, yielded by the inversion, confirm the presence of oceanic crust beneath the Ionian Sea. The thickness of the Ionian oceanic lithosphere is around 180 km, whereas the continental lithosphere beneath the eastern Levant Basin is ~70 km thick, with low crustal Vp/Vs (~1.7) and Poisson’s (~0.24) ratios. According to 3-D shear wave velocity tomography using the surface wave data, the thickness of the oceanic lithosphere increases from the Triassic Ionian Sea towards the Permian-Carboniferous Libyan Sea and Herodotus Basin. Thicknesses of the Permo-Triassic oceanic lithosphere considerably larger than 100 km indicate that oceanic lithosphere can thicken by cooling substantially beyond the limits suggested by the plate cooling model. The transition from oceanic to continental lithosphere occurs at about 31°E in the crust, as indicated by magnetic and gravity measurements. The continental mantle lithosphere further to the east of this boundary is ~150 km thick beneath the westernmost Levant Basin, as indicated by shear wave velocity tomography and long wavelength gravity anomalies, and strongly thins eastward towards the area of the Levantine Coast and the Dead Sea Fault. The localization of the lithospheric deformation and crustal seismicity along the Dead Sea Fault correlates spatially with the thinning of the underlying continental lithosphere.

Key words: surface wave tomography, wide angle seismic imaging, joint inversion, Vp/Vs and Poisson’s ratios, eastern Mediterranean, Oceanic Lithosphere, Continental Lithosphere, Dead Sea Fault.
Long term stability of dynamic reference systems for NO2 atmospheric monitoring
Authors: Flores Edgar , Idrees Faraz , Moussay Philippe , Wielgosz Robert I.
Published: March 2021

The long-term monitoring of reactive gases, such as NO2, provides significant challenges for the development of gas standards that can demonstrate fit-for-purpose stability and accuracy.  Over the last fifteen years the BIPM’s primary gas facility for the dynamic production of mixtures of nitrogen dioxide in nitrogen, operating over the range (1 μmol/mol to 15 μmol/mol) has been shown to operate with a relative standards uncertainty of 0.4%. The system is based on continuous weighing of a permeation tube and on the accurate impurity quantification and correction of the gas mixtures using FT-IR.

The operation of the system has been demonstrated in two international comparisons organized by the CCQM Working Group on Gas Analysis (CCQM-GAWG), in 2009 and 2018, with the former demonstrating the requirement to correct for HNO3 impurities in gas standards produced in cylinders, and the more recent, the potential for non-linear decay in NO2 concentration in gas cylinder standards in the first 100 to 150 days following their production.

The CCQM-K74 (2009/2010) was organized, with all cylinders prepared by the one NMI (VSL) with the same surface treatment and characterized for stability and with reference values provided by the BIPM dynamic reference facility. The initial comparison identified small decay rates in the circulated standards, accounted for by the addition of an uncertainty to the reference value, and calculated to have been no more than 0.1 nmol/mol per day loss of NO2. However, the 2009 comparison did not examine standards maintained by individual participating institutes directly. The protocol of the CCQM-K74.2018 comparison, was modified so that the standards prepared by participating institutes (two per participant), were all directly measured at the BIPM against its dynamic reference facility. The modified protocol, although technically more challenging, has allowed the different decay rates in different cylinder preparations from different institutes to be identified, as well as the time dependence of these days rates.

The work has highlighted the challenges in NO2 standard development, and that fit-for-purpose standards can be obtained following appropriate protocols. Further development of these protocols is the focus of a number of research programmes, for example  METNO2 and MetroPEMS projects within the EMPIR programmes. Further activities at the BIPM facility are focused on validating the performance of NO2 dynamic reference systems below 1 μmol/mol and into the nmol/mol range, with the comparison of different dynamic reference systems, in support of future international comparisons and knowledge transfer activities.
A First Assessment of the interconnection between celestial pole offset and geomagnetic field variations
Authors: Modiri Sadegh , Heinkelmann Robert , Belda Santiago , Hoseini Mostafa , Korte Monika , Malkin Zinovy , Ferrándiz José M. , Schuh Harald
Published: March 2021

The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) provides the geodetic infrastructure needed to monitor the Earth system.. The understanding of forced temporal variations of celestial pole motion (CPM) could bring us significantly closer to meeting the GGOS goals (i.e. 1 mm accuracy and 0.1 mm/year stability on global scales in terms of the ITRF defining parameters). Besides astronomical forcing, CPM excitation depends on the processes in the fluid core and the core-mantle boundary. The same processes are responsible for the variations of the geomagnetic field (GMF). This study investigates the interconnection between the celestial pole offset (CPO) and effective geophysical processes that contribute to the Earth's rotational variation. We use the CPO time series obtained from very long baseline interferometry (VLBI) observations together with the latest GMF data such as geomagnetic jerk and magnetic dipole moment, and a state-of-the-art geomagnetic field model to explore the correlation between CPM and GMF. 
Our results confirm the findings of previous studies, revealing that  substantial free core nutation (FCN) disturbance occurred at the epochs close to the GMJ events. The results also reveal some common features in the FCN and GMF variation, which show the potential to improve knowledge regarding the GMF's contribution to the Earth's rotation.
In-situ U-(Th-)Pb dating and REE analysis of zircon and monazite in the Grt-bearing gneisses from Gossa: Tracing early subduction into the highest-grade domains of the Western Gneiss Region, Norway
Authors: Jeanneret Pauline , Walczak Katarzyna , Majka Jarosław , Bukała Michał , Cuthbert Simon , Kooijman Ellen
Published: March 2021

To better understand the subduction–exhumation cycles of the Baltoscandian margin that reached (U)HP depths during the Caledonian orogeny, we have performed in-situ U-(Th-)Pb dating coupled with REE analysis of zircon and ± monazite in four samples from the supracrustal rocks of the Blåhø Nappe on Gossa island in the Western Gneiss Region (WGR) of Norway. We dated two garnet-plagioclase-biotite gneisses and two garnet-plagioclase-amphibole gneisses. Our research focused on deciphering the early metamorphic evolution of these complex rocks that have been overprinted by exhumation-related structures and pervasive retrogressive metamorphism.

The dated zircon grains are spherical or slightly elongated in shape, some of which display clear multi-stage growth features. Only one grain armored by garnet preserved an older detrital core that yielded early Neoproterozoic dates between 1.1-1.0 Ga. This grain does not provide any Caledonian signal. Younger individual 206Pb/238U dates show three distinct populations that yield three concordia ages, each obtained from distinctly different compositional domains, the oldest from cores and the two youngest from overgrowths. The cores are characterized by HREE enrichment (high Lu/Gd ratios ca. 14.5), high Th/U ratios (> 0.1), and large Eu anomalies. They yield a concordia age of 474 ± 6.4 Ma. These cores can be rimmed by two different types of zircon overgrowth. The first overgrowth type (1) displays the same REE pattern as the cores and gives a concordia age of 444± 4.3 Ma. The second overgrowth type (2) shows a very weak Eu anomaly, no HREE enrichment (low Lu/Gd ratios ca. 2.37) and a very low Th/U ratios (<0.1). These yield a concordia age of 416± 3.7 Ma. The two older U–Pb zircon age populations are tentatively interpreted as reflecting two distinct metamorphic events or a prolonged episode of metamorphism. The youngest concordant metamorphic zircon dates a high grade, probably (U)HP, metamorphic overprint at ca. 416 Ma, subsequent to the previous events. Analyses performed on monazite provided complementary age records to those obtained on zircon. Monazite grains are weakly zoned, exhibit wormy shapes and are aligned with the youngest foliation. Th–U–total Pb dating of monazite, coupled with major and trace element mapping of monazite, yielded a very homogeneous age of 382 ± 1.6 Ma (n=65) interpreted to date the late shearing, which possibly accommodated a late stage of exhumation.

Funded by the National Science Centre (Poland) project no. 2014/14/E/ST10/00321.

 
New operational nowcasting system at Finnish Meteorological Institute
Authors: Hieta Leila , Partio Mikko , Laine Marko , Tuomola Marja-Liisa , Hohti Harri , Perttula Tuuli , Gregow Erik , Ylhäisi Jussi
Published: March 2021

Rapidly updating nowcasting system, Smartmet nowcast, has been developed at Finnish Meteorological Institute (FMI). The system combines information from multiple sources to operationally produce accurate and timely short range forecasts and a detailed description of the present weather to the end-users. The information sources combined are 1) Rapidly-updating high-resolution numerical weather prediction (NWP) MetCoOp nowcast (MNWC) forecast 2) radar-based nowcast 3) 10-day operational forecast. The Smartmet nowcast is currently produced for parameters 2-m temperature, 10-m wind speed, relative humidity, total cloud cover and accumulated 1-hour precipitation.

The system produces hourly updating nowcast information over the Scandinavian forecast domain and combines it seamlessly with the 10-day operational forecast information. Prior the combination a simple bias correction scheme based on recent forecast error information is applied to MNWC model analysis and forecast fields of 2-m temperature, relative humidity and 10-m wind speed. The blending of the nowcast and the 10-day operational forecast information is done using Optical-flow based image morphing method, which provides visually seamless forecasts for each forecast variable.

FMI has operationally produced Smartmet nowcast forecasts since September 2020. The validation of the data is in progress. The available results show that the Smartmet nowcast is improving the quality of short range forecasts and producing seamless and consistent forecasts. The method is also reducing the delay of forecast production. The Smartmet nowcast method will be automated in FMI forecast production in the near future.
Solar Induced Fluorescence measured from satellite sensors captures mostly structural than physiological responses to environmental stressors
Authors: Paschalis Athanasios , Gentine Pierre , Graham Duncan , Fatichi Simone
Published: March 2021

A deep understanding of the responses of terrestrial vegetation to environmental forcing is crucial for understanding the global carbon dynamics, especially under a changing climate. Vegetation responses to stress can manifest first as plant physiological responses, and at later stages through changes in canopy structure. Remote sensing of vegetation has been proven very valuable in providing such understanding. One of the major breakthroughs has been the use of multi and hyper spectral sensors on board satellites that can retrieve Solar Induced Fluorescence (SIF), which is closely linked with plant photosynthesis.

In this study we assess whether (SIF), as observed by instruments on board of satellites, can adequately capture both of those responses. Using 7 different global SIF products, water and CO2 flux data from 120 eddy-covariance towers and climate reanalysis products, we found a good agreement between the 16-day responses of flux tower observed gross primary productivity (GPP) and SIF to soil moisture and light, and a weaker agreement regarding the responses to temperature and atmospheric humidity. Overall, we found that current satellite SIF responses to environmental stressors mostly reflect structural changes in vegetation structure, and that satellite SIF has limited skill in capturing early stress plant physiological responses except for the light availability response at higher latitudes. While satellite SIF significantly outperforms more traditional vegetation indices (EVI, NDVI), as it does not saturate unlike the latter ones, it does not provide major additional information regarding vegetation physiological responses to either hydrological or atmospheric droughts.
Long-term changes in inorganic carbon in the Elbe estuary
Authors: Rewrie Louise , Voynova Yoana , Brix Holger , Ollesch Gregor , Baschek Burkard
Published: March 2021

Overall, estuaries are net CO2 sources to the atmosphere, releasing an estimated 0.25 Pg C yr-1, which could counterbalance the shelf uptake of approximately 0.25 Pg C yr-1. River discharge can influence both, the CO2 flux from estuary to the atmosphere, as well as the magnitude of dissolved inorganic carbon (DIC) exported to coastal waters. In Europe, climate change is expected to cause an increased precipitation in winter and longer periods of drought in summer. The goal of this study is to elucidate the influence of climate-change-induced hydrological changes on an estuarine carbonate system.

The Elbe River is one largest river basins in central Europe, where over 24 million people live in the catchment area. Since 2014, annual Elbe river discharge has been relatively low at 492.95 m3 s-1, compared to the mean river discharge from 2008 to 2018 at 652.95 m3 s-1. 2018 was especially dry, with a discharge of 441 m3 s-1, the lowest annual mean river discharge since 1992. The Elbe estuary has been extensively sampled by the Flussgebietsgemeinschaft (FGG) Elbe (Elbe River Basin Community), qualifying the region as a suitable site to study the natural and anthropogenic impacts on estuarine systems.

Preliminary results of the 1985-2018 FGG dataset indicate a major shift in the carbonate system dynamics in the Elbe estuary. From assessing the behaviour of DIC and other ecosystem parameters along the estuary over time, the region can be separated into three ecosystem states. During the time of high pollution, from 1985 to 1990, the estuary exhibited high levels of DIC. Between 1991 and 1996 is the transitional period. After 1997, the ecosystem parameters appear to be exhibiting similar patterns throughout each year with similar levels and therefore this period can be classified as the current ecosystem state. Since 1997, DIC exhibits a drawdown in spring and summer months in the upper region, coinciding with the increase in dissolved oxygen saturation and pH, which can indicate that this region is net autotrophic. Further downstream, DIC then increases along the estuary, and often peaks in the maximum turbidity zone.

For this study, we apply multiple linear regression to determine the relative importance of ecosystem variables that contribute to annual and monthly DIC variability in the recent ecosystem state. Key ecosystem variables include particulate and dissolved organic carbon, pH, dissolved oxygen and river discharge.
A Proton Flux Model Dedicated to Solar Arrays Degradations on Electric Orbit Raising Missions
Authors: Brunet Antoine , Sicard Angélica , Papadimitriou Constantinos , Lazaro Didier
Published: March 2021

Electric Orbit Raising (EOR) for telecommunication satellites has allowed significant reduction in onboard fuel mass, at the price of extended transfer durations. These relatively long orbital transfers, which can take up to a few months, equatorially cross most of the radiation belts, resulting in significant exposure of the spacecraft to space radiations. Since there are not covered by many spacecrafts, the radiation environment of intermediate regions of the radiation belts is less known than on popular orbits such as LEO or GEO. In particular, there is a need for more specific models for the MeV energy range proton fluxes, responsible for solar arrays degradations. We present a model of proton fluxes dedicated for EOR missions that was developped as part of the ESA ARTES program. This model is able to estimate the average proton fluxes between 60 keV and 10MeV on arbitrary trajectories on the typical durations of EOR transfers. A global statistical model of the radiation belts was extracted from the Van Allen Probes (RBSP) RBSPICE data and enriched by simulation results from the Salammbô radiation belt model were used. A special care was taken to model the temporal dynamics of the proton belt, allowing to compute analytically the distribution of the average fluxes on arbitrary EOR missions.
Phosphorus forms in technosols afforested with N-fixing and non-N-fixing tree species 
Authors: Sroka Katarzyna , Chodak Marcin , Pietrzykowski Marcin
Published: March 2021

Tree species capable of forming a symbiosis with N-fixing bacteria may affect P availability in reclaimed technosols. The objective of this study was to compare the effect of N-fixing tree species and non-N-fixing species on phosphorus forms in technosols developing from various materials. Soil samples were taken under black locust (Robinia pseudoaccaccia), black alder (Alnus glutinosa), silver birch (Betula pendula) and Scots pine (Pinus sylvestris) from two depths (0-5 cm and 5 – 20 cm). The soil substrates were fly ashes, sands and clays. In the soil samples measured were concentrations of total P (Pt),  water soluble P (PH2O),  dilute salt-extractable P (Pex), microbial biomass P (Pmic) and total labile P (Plabil). Multifactor ANOVA revealed that tree species did not influence contents of Pt, Pex and PH20. However, there was a statistically significant effect of soil substrate and soil horizon on these forms of P. The factors tree species, soil substrate and soil horizon had statistically significant effect on Pmic content whereas content of Plabil was affected by tree species and soil horizon. Multiple Range Tests by tree species showed that soils under Scots pine contained significantly less Pmic than soils under other tree species studied. There were no significant differences in Pmic between the soils under silver birch, black alder and black locust. The soils under Scots pine contained also significantly less Plabil than the soils under black locust and silver birch. Our study included P forms that are considered labile (except Pt). The obtained results indicated that the effect of N-fixing trees on these forms of P was weak. Instead we noticed that Scots pine had negative effect on some forms of labile P. 

The study was financed by The National Science Centre, Poland, grant No. 2018/31/B/ST10/01626.
Validation of TROPOMI nadir ozone profile retrievals: Methodology and first results
Authors: Keppens Arno , Lambert Jean-Christopher , Hubert Daan , Compernolle Steven , Verhoelst Tijl , Niemeijer Sander , Fjaeraa Ann Mari , ter Linden Mark , Sneep Maarten , de Haan Johan , Veefkind Pepijn ,   CHEOPS-5p validation team
Published: March 2021

Part of the space segment of EU’s Copernicus Earth Observation programme, the Sentinel-5 Precursor (S5P) mission is dedicated to global and European atmospheric composition measurements of air quality, climate and the stratospheric ozone layer. On board of the S5P early afternoon polar satellite, the imaging spectrometer TROPOMI (TROPOspheric Monitoring Instrument) performs nadir measurements of the Earth radiance within the UV-visible and near-infrared spectral ranges, from which atmospheric ozone profile data are retrieved. Developed at the Royal Netherlands Meteorological Institute (KNMI) and based on the optimal estimation method, TROPOMI’s operational ozone profile retrieval algorithm has recently been upgraded. With respect to early retrieval attempts, accuracy is expected to have improved significantly, also thanks to recent updates of the TROPOMI Level-1b data product. This work reports on the initial validation of the improved TROPOMI height-resolved ozone data in the troposphere and stratosphere, as collected both from the operational S5P Mission Performance Centre/Validation Data Analysis Facility (MPC/VDAF) and from the S5PVT scientific project CHEOPS-5p. Based on the same validation best practices as developed for and applied to heritage sensors like GOME-2, OMI and IASI (Keppens et al., 2015, 2018), the validation methodology relies on the analysis of data retrieval diagnostics – like the averaging kernels’ information content – and on comparisons of TROPOMI data with reference ozone profile measurements. The latter are acquired by ozonesonde, stratospheric lidar, and tropospheric lidar stations performing network operation in the context of WMO's Global Atmosphere Watch and its contributing networks NDACC and SHADOZ. The dependence of TROPOMI’s ozone profile uncertainty on several influence quantities like cloud fraction and measurement parameters like sun and scan angles is examined and discussed. This work concludes with a set of quality indicators, enabling users to verify the fitness-for-purpose of the S5P data.
Modeling of TEC over the Iberian Peninsula using PCA decomposition and multiple linear regression on space weather parameters
Authors: Morozova Anna , Barlyaeva Tatiana , Barata Teresa
Published: March 2021

The total electron content (TEC) over the Iberian Peninsula was modeled using a three-step procedure. At the 1st step the TEC series is decomposed using the principal component analysis (PCA) into several daily modes. Then, the amplitudes of those daily modes is fitted by a multiple linear regression model (MRM) using several types of space weather parameters as regressors. Finally, the TEC series is reconstructed using the PCA daily modes and MRM fitted amplitudes.

The advantage of such approach is that seasonal variations of the TEC daily modes are automatically extracted by PCA. As space weather parameters we considered proxies for the solar UV and XR fluxes, number of the solar flares, parameters of the solar wind and the interplanetary magnetic field, and geomagnetic indices. Different time lags and combinations of the regressors are tested.

The possibility to use such TEC models for forecasting was tested. Also, a possibility to use neural networks (NN) instead of MRM is studied.
QA4SM – An online tool for satellite soil moisture data validation
Authors: Scherrer Samuel , Preimesberger Wolfgang , Tercjak Monika , Bakcsa Zoltan , Boresch Alexander , Dorigo Wouter
Published: March 2021

To validate satellite soil moisture products and compare their quality with other products, standardized, fully traceable validation methods are required. The QA4SM (Quality Assurance for Soil Moisture; ) free online validation tool provides an easy-to-use implementation of community best practices and requirements set by the Global Climate Observing System and the Committee on Earth Observation Satellites. It sets the basis for a community wide standard for validation studies.

QA4SM can be used to preprocess, intercompare, store, and visualise validation results. It uses state-of-the-art open-access soil moisture data records such as the European Space Agency’s Climate Change Initiative (ESA CCI) and the Copernicus Climate Change Services (C3S) soil moisture datasets, as well as single-sensor products, e.g. H-SAF Metop-A/B ASCAT surface soil moisture, SMOS-IC, and SMAP L3 soil moisture. Non-satellite data include in-situ data from the International Soil Moisture Network (ISMN: ), as well as land surface model or reanalysis products, e.g. ERA5 soil moisture.

Users can interactively choose temporal or spatial subsets of the data and apply filters on quality flags. Additionally, validation of anomalies and application of different scaling methods are possible. The tool provides traditional validation metrics for dataset pairs (e.g. correlation, RMSD) as well as triple collocation metrics for dataset triples. All results can be visualised on the webpage, downloaded as figures, or downloaded in NetCDF format for further use. Archiving and publishing features allow users to easily store and share validation results. Published validation results can be cited in reports and publications via DOIs.

The new version of the service provides support for high-resolution soil moisture products (from Sentinel-1), additional datasets, and improved usability.

We present an overview and examples of the online tool, new features, and give an outlook on future developments.

Acknowledgements: This work was supported by the QA4SM & QA4SM-HR projects, funded by the Austrian Space Applications Programme (FFG).
Weather regimes in South East Asia: Sub-seasonal predictability of the regimes and the associated high impact weather  
Authors: Gonzalez Paula , Howard Emma , Thomas Simon , Frame Thomas , Martinez-Alvarado Oscar , Methven John , Woolnough Steven
Published: March 2021

This work considers the sub-seasonal predictability of two sets of weather regimes for South East Asia: a two-tiered assignment, that first considers large-scale patterns and then assigns synoptic-scale regimes, and a flat classification, which only considers the synoptic scale. In the two-tiered approach, the tier 1 large-scale regimes, which capture ENSO and seasonal variations, are each partitioned into South East Asia regional clusters that capture synoptic variability.   

The sub-seasonal predictability of both the standard and tiered regimes is assessed using UKMO GloSea5 hindcasts and forecasts for lead times of up to 5 weeks. We find that the GloSea5 system presents an accurate representation of the regimes’ climatology and a good level of skill for their assignment. Nonetheless, the predictability depends on the specific regimes and some significant forecast drifts are also identified. Additionally, the predictive skill of high impact precipitation events obtained statistically from the prediction of the regimes is assessed and compared with the probabilistic precipitation forecasts of the GloSea5 ensemble.    

A description of the regime classification methodology and their connections to seasonal and synoptic phenomena will be discussed in a separate presentation, titled “Weather regimes in South East Asia: connections with synoptic phenomena and high impact weather” and presented by Emma Howard. 
Building a coupled data assimilation system for the atmosphere, land-surface and subsurface on the catchment scale
Authors: Schalge Bernd , Haese Barbara , Waldowski Bastian , Brandhorst Natascha , Sanchez Emilio , Pui Hung Ching , Lv Shaoning , Schüler Lennart , Kunstmann Harald , Cirpka Olaf , Attinger Sabine , Kollet Stefan , Neuweiler Insa , Hendricks Franssen Harrie-Jan , Simmer Clemens
Published: March 2021

We present a data assimilation (DA) system for the atmosphere-land-surface-subsurface system on the catchment scale. The Neckar catchment in SW-Germany served as the specific case where the DA in combination with the coupled atmosphere-land surface-subsurface model TSMP was used. TSMP couples the atmospheric model COSMO, the land-surface model CLM and the hydrological model ParFlow to the DA framework PDAF. We will discuss how the ensemble system is set up in order to work properly and what issues we faced during our initial testing. For the atmosphere we found that it is important to have a good ensemble of lateral forcings as changing internal parameters for various parametrizations does not introduce sufficient variability on its own due to the rather small size of our domain. For the sub-surface the choice of parameters becomes most important and as such parameter estimation will be a valuable tool for improving DA results significantly. Finally, we are showing some first DA results with our system concerning soil moisture with two different assimilation methods with a fully coupled model setup. In the first assimilation scenario in-situ soil moisture data measured by cosmic ray probes are assimilated, while in the second assimilation scenario remotely sensed near surface soil moisture is assimilated. The first results are encouraging and we discuss additional planned simulation scenarios with the fully coupled atmosphere-land surface-subsurface modelling system as well as plans to test strongly coupled DA, where measurements are used to update states across compartments, possibly resulting in additional accuracy gain compared to traditional uncoupled DA.

 
Spatial and temporal variations of seismicity during the Maurienne swarm (French Alps): short- and long-term migrations and b-value dependence with depth
Authors: Minetto Riccardo , Hemlstetter Agnès , Guéguen Philippe , Langlais Mickaël
Published: March 2021

We analyse the spatio-temporal variations of the seismicity recorded during the Maurienne swarm. The Maurienne swarm occurred between 2017 and 2018 in the French Alps in the central part of the external crystalline massif of Belledonne. This massif extends for more than 120km in N30 direction, it is bounded to the west by the wide topographic depression of the Isère valley and the Combe de Savoie, and it is crosscut by the Maurienne valley.  The location and the 3D shape of the seismic swarm are consistent with an outcroping N80 vertical fault zone. The seismic activity is interpreted as a result of the reactivation of this inherited vertical fault system. The largest event had a magnitude of 3.5.

We used a catalog of 58000 events that were detected using template-matching and relocated with a double-difference method.  
We show that the swarm is characterised by short-term (days) and long-term (months) migrations that may be related to the presence of fluids. 
We also observe that the b-value decreases with depth and we discuss how this variation may due to shallow fault systems whose geometry differs from the one of the main fault system. 
Part of the events occurred when only one station was active. This study shows that, by grouping earthquakes into groups of similar events (clusters), it is possible to study spatio-temporal variations in such conditions.
Dating of ice cores from temperate glaciers - Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core
Authors: Jenk Theo , Festi Daniela , Schwikowski Margit , Maggi Valter , Oeggl Klaus
Published: March 2021

Dating glaciers is an arduous yet essential task in ice core studies, which becomes even more challenging for the dating of glaciers suffering from mass loss in the accumulation zone as result of climate warming. In this context, we present the dating of a 46 m deep ice core from the Central Italian Alps retrieved in 2016 from the Adamello glacier (Pian di Neve, 3100 m a.s.l.). We will show how the timescale for the core could be obtained by integrating results from the analyses of the radionuclides 210Pb and 137Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results clearly indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years and that the 46 m ice core reaches back to around 1944. Despite the severe mass loss affecting this glacier even in the accumulation zone, we show that it is possible to obtain a reliable timescale for such a temperate glacier. These results are very encouraging and open new perspectives on the potential of such glaciers as informative palaeoarchives. We thus consider it important to present our dating approach to a broader audience.
The effects of seismic anisotropy on  S-wave travel time-tomography: the problem of apparent anomalies and possible solutions
Authors: Rappisi Francesco , Vanderbeek Brandon Paul , Faccenda Manuele
Published: March 2021

Teleseismic travel-time tomography remains one of the most popular methods for obtaining images of Earth's upper mantle. While teleseismic shear phases, most notably SKS, are commonly used to infer the anisotropic properties of the upper mantle, anisotropic structure is often ignored in the construction of body wave shear velocity models. Numerous researchers have demonstrated that neglecting anisotropy in P-wave tomography can introduce significant imaging artefacts that could lead to spurious interpretations. Less attention has been given to the effect of anisotropy on S-wave tomography partly because, unlike P-waves, there is not a ray-based methodology for modelling S-wave travel-times through anisotropic media. Here we evaluate the effect that the isotropic approximation has on tomographic images of the subsurface when shear waves are affected by realistic mantle anisotropy patterns. We use SPECFEM to model the teleseismic shear wavefield through a geodynamic model of subduction that includes elastic anisotropy predicted from micromechanical models of polymineralic aggregates advected through the simulated flow field. We explore how the chosen coordinates system in which S-wave arrival times are measured (e.g., radial versus transverse) affects the imaging results. In all cases, the isotropic imaging assumption leads to numerous artefacts in the recovered velocity models that could result in misguided inferences regarding mantle dynamics. We find that when S-wave travel-times are measured in the direction of polarisation, the apparent anisotropic shear velocity can be approximated using sinusoidal functions of period pi and two-pi. This observation allows us to use ray-based methods to predict S-wave travel-times through anisotropic models. We show that this parameterisation can be used to invert S-wave travel-times for the orientation and strength of anisotropy in a manner similar to anisotropic P-wave travel-time tomography. In doing so, the magnitude of imaging artefacts in the shear velocity models is greatly reduced.