Benchmark campaign and case study episode in central Europe for development and assessment of advanced GNSS tropospheric models and products

Initial objectives and design of the Benchmark campaign organized within the European COST Action ES1206 (2013–2017) are described in the paper. This campaign has aimed to support the development and validation of advanced Global Navigation Satellite System (GNSS) tropospheric products, in particular high-resolution and ultra-fast zenith total delays (ZTDs) and tropospheric gradients derived from a dense permanent network. A complex data set was collected for the 8-week period when several extreme heavy precipitation episodes occurred in central Europe which caused severe river floods in this area. An initial processing of data sets from GNSS products and numerical weather models (NWMs) provided independently estimated reference parameters – zenith tropospheric delays and tropospheric horizontal gradients. Their provision gave an overview about the product similarities and complementarities, and thus a potential for improvements of a synergy in their optimal exploitations in future. Reference GNSS and NWM results were intercompared and visually analysed using animated maps. ZTDs from two reference GNSS solutions compared to global ERA-Interim reanalysis resulted in accuracy at the 10 mm level in terms of the root mean square (rms) with a negligible overall bias, comparisons to Global Forecast System (GFS) forecasts showed accuracy at the 12 mm level with the overall bias of −5 mm and, finally, comparisons to mesoscale ALADIN-CZ forecast resulted in accuracy at the 8 mm level with a negligible total bias. The comparison of horizontal tropospheric gradients from GNSS and NWM data demonstrated a very good agreement among independent solutions with negligible biases and an accuracy of about 0.5 mm. Visual comparisons of maps of zenith wet delays and tropospheric horizontal gradients showed very promising results for future exploitations of advanced GNSS tropospheric products in meteorological applications, such as severe weather event monitoring and weather nowcasting. The GNSS products revealed a capability of providing more detailed structures in atmosphere than the state-of-the-art numerical weather models are able to capture. In an initial study on the contribution of hydrometeors (e.g. cloud water, ice or snow) to GNSS signal delays during severe weather, the effect reached up to 17 mm, and it was suggested that hydrometeors should be carefully accounted for within the functional model. The reference products will be further exploited in various specific studies using the Benchmark data set. It is thus going to play a key role in these highly interdisciplinary developments towards better mutual benefits from advanced GNSS and meteorological products.Web of Science973008298

A GPS network for tropospheric tomography in the framework of the Mediterranean hydrometeorological observatory Cévennes-Vivarais (south-eastern France)

International audienceThe Mediterranean hydrometeorological observatory Cévennes-Vivarais (OHM-CV) coordinates hydrometeorological observations (radars, rain gauges, water level stations) on a regional scale in southeastern France. In the framework of OHM-CV, temporary GPS measurements have been carried out for 2 months in autumn 2002, when the heaviest rainfall are expected. These measurements increase the spatial density of the existing permanent GPS network, by adding three more receivers between the Mediterranean coast and the Cévennes-Vivarais range to monitor maritime source of water vapour flow feeding the precipitating systems over the Cévennes-Vivarais region. In addition, a local network of 18 receivers covered an area of 30 by 30 km within the field of view of the meteorological radar. These regional and local networks of permanent and temporary stations are used to monitor the precipitable water vapour (PWV) with high temporal resolution (15 min). Also, the dense local network provided data which have been inverted using tomographic techniques to obtain the 3-D field of tropospheric water vapour content. This study presents methodological tests for retrieving GPS tropospheric observations from dense networks, with the aim of assessing the uncertainties of GPS retrievals. Using optimal tropospheric GPS retrieval methods, high resolution measurements of PWV on a local scale (a few kilometres) are discussed for rain events. Finally, the results of 3-D fields of water vapour densities from GPS tomography are analysed with respect to precipitation fields derived from a meteorological radar, showing a good correlation between precipitation and water vapour depletion areas

Inter-technique validation of tropospheric slant total delays

An extensive validation of line-of-sight tropospheric slant total delays (STD) from Global Navigation Satellite Systems (GNSS), ray tracing in numerical weather prediction model (NWM) fields and microwave water vapour radiometer (WVR) is presented. Ten GNSS reference stations, including collocated sites, and almost 2 months of data from 2013, including severe weather events were used for comparison. Seven institutions delivered their STDs based on GNSS observations processed using 5 software programs and 11 strategies enabling to compare rather different solutions and to assess the impact of several aspects of the processing strategy. STDs from NWM ray tracing came from three institutions using three different NWMs and ray-tracing software. Inter-techniques evaluations demonstrated a good mutual agreement of various GNSS STD solutions compared to NWM and WVR STDs. The mean bias among GNSS solutions not considering post-fit residuals in STDs was -0.6 mm for STDs scaled in the zenith direction and the mean standard deviation was 3.7 mm. Standard deviations of comparisons between GNSS and NWM ray-tracing solutions were typically 10 mm +/- 2 mm (scaled in the zenith direction), depending on the NWM model and the GNSS station. Comparing GNSS versus WVR STDs reached standard deviations of 12 mm +/- 2 mm also scaled in the zenith direction. Impacts of raw GNSS post-fit residuals and cleaned residuals on optimal reconstructing of GNSS STDs were evaluated at intertechnique comparison and for GNSS at collocated sites. The use of raw post-fit residuals is not generally recommended as they might contain strong systematic effects, as demonstrated in the case of station LDB0. Simplified STDs reconstructed only from estimated GNSS tropospheric parameters, i.e. without applying post-fit residuals, performed the best in all the comparisons; however, it obviously missed part of tropospheric signals due to non-linear temporal and spatial variations in the troposphere. Although the post-fit residuals cleaned of visible systematic errors generally showed a slightly worse performance, they contained significant tropospheric signal on top of the simplified model. They are thus recommended for the reconstruction of STDs, particularly during high variability in the troposphere. Cleaned residuals also showed a stable performance during ordinary days while containing promising information about the troposphere at low-elevation angles.Web of Science1062208218

EUNADICS-AV early warning system dedicated to supporting aviation in the case of a crisis from natural airborne hazards and radionuclide clouds

The purpose of the EUNADICS-AV (European Natural Airborne Disaster Information and Coordination System for Aviation) prototype early warning system (EWS) is to develop the combined use of harmonised data products from satellite, ground-based and in situ instruments to produce alerts of airborne hazards (volcanic, dust, smoke and radionuclide clouds), satisfying the requirement of aviation air traffic management (ATM) stakeholders (https://cordis.europa.eu/project/id/723986, last access: 5 November 2021). The alert products developed by the EUNADICS-AV EWS, i.e. near-real-time (NRT) observations, email notifications and netCDF (Network Common Data Form) alert data products (called NCAP files), have shown significant interest in using selective detection of natural airborne hazards from polar-orbiting satellites. The combination of several sensors inside a single global system demonstrates the advantage of using a triggered approach to obtain selective detection from observations, which cannot initially discriminate the different aerosol types. Satellite products from hyperspectral ultraviolet–visible (UV–vis) and infrared (IR) sensors (e.g. TROPOMI – TROPOspheric Monitoring Instrument – and IASI – Infrared Atmospheric Sounding Interferometer) and a broadband geostationary imager (Spinning Enhanced Visible and InfraRed Imager; SEVIRI) and retrievals from ground-based networks (e.g. EARLINET – European Aerosol Research Lidar Network, E-PROFILE and the regional network from volcano observatories) are combined by our system to create tailored alert products (e.g. selective ash detection, SO2 column and plume height, dust cloud, and smoke from wildfires). A total of 23 different alert products are implemented, using 1 geostationary and 13 polar-orbiting satellite platforms, 3 external existing service, and 2 EU and 2 regional ground-based networks. This allows for the identification and the tracking of extreme events. The EUNADICS-AV EWS has also shown the need to implement a future relay of radiological data (gamma dose rate and radionuclides concentrations in ground-level air) in the case of a nuclear accident. This highlights the interest of operating early warnings with the use of a homogenised dataset. For the four types of airborne hazard, the EUNADICS-AV EWS has demonstrated its capability to provide NRT alert data products to trigger data assimilation and dispersion modelling providing forecasts and inverse modelling for source term estimate. Not all of our alert data products (NCAP files) are publicly disseminated. Access to our alert products is currently restricted to key users (i.e. Volcanic Ash Advisory Centres, national meteorological services, the World Meteorological Organization, governments, volcano observatories and research collaborators), as these are considered pre-decisional products. On the other hand, thanks to the EUNADICS-AV–SACS (Support to Aviation Control Service) web interface (https://sacs.aeronomie.be, last access: 5 November 2021), the main part of the satellite observations used by the EUNADICS-AV EWS is shown in NRT, with public email notification of volcanic emission and delivery of tailored images and NCAP files. All of the ATM stakeholders (e.g. pilots, airlines and passengers) can access these alert products through this free channel.Peer ReviewedArticle escrit per 46 autors/es: Hugues Brenot Nicolas Theys Lieven Clarisse Jeroen van Gent Daniel Hurtmans Sophie Vandenbussche Nikolaos Papagiannopoulos Lucia Mona Timo Virtanen Andreas Uppstu Mikhail Sofiev Luca Bugliaro Margarita Vázquez-Navarro Pascal Hedelt Michelle Maree Parks Sara Barsotti Mauro Coltelli William Moreland Simona Scollo Giuseppe Salerno Delia Arnold-Arias Marcus Hirtl Tuomas Peltonen Juhani Lahtinen Klaus Sievers Florian Lipok Rolf Rüfenacht Alexander Haefele Maxime Hervo Saskia Wagenaar Wim Som de Cerff Jos de Laat Arnoud Apituley Piet Stammes Quentin Laffineur Andy Delcloo Robertson Lennart Carl-Herbert Rokitansky Arturo Vargas Markus Kerschbaum Christian Resch Raimund Zopp Matthieu Plu 1 Vincent-Henri Peuch Michel van Roozendael Gerhard WotawaPostprint (author's final draft

Global Monitoring of Volcanic SO2 Degassing Using Sentinel-5 Precursor Tropomi

We present here the TROPOMI SO 2 product, which is publicly available since April 2018. We describe the capabilities and limitations of the product for the monitoring of volcanic SO 2 degassing. With several examples, we illustrate the benefit of a small satellite pixel of 3.5 x 5.5 km 2 . Owing to its improved detection limit, the data can be used to generate time series of SO 2 mass over number of volcanoes, with a large range of SO 2 emissions. We use Nyiragongo as a show case and correlate the SO 2 mass data with lava lake level estimates and local measurements of the seismicity. This paper also presents on-going developments to further improve the performance of the product for weak SO 2 loadings using a new algorithm, COBRA

Prototype of multi-hazard early warning from EUNADICS-AV systems to trigger model forecasts of European airspace

info:eu-repo/semantics/nonPublishe

Potentiel de la mesure GPS sol pour l'étude des pluies intenses méditerranéennes.

mail perso: [email protected] Cévennes-Vivarais and the surrounding area up to the Mediterranean has been chosen by the OHM-CV (Mediterranean Hydrometeorological Observatory of the Cévennes-Vivarais) for the frequence and representativity of the intense rainfalls that affect this area. Since 2002, autumnal campaigns of GPS measurements have taken place there to try to improve our understanding of the tropospheric water vapor field which is associated with the intenses rainfalls. GPS meteorological observations are ZTD (Zenith Total tropospheric Delay) and gradients of delays. Expressed by an East-West component (Gew) and a North-South component (Gns), the gradient of delay shows the anisotropy of the water vapor field around GPS site.For the analysis of GPS observations of permanent and temporary networks of the OHM-CV region, an optimal configuration has been researched considering different sensitivity tests. An accuracy of 5 mm can be obtained for ZTD, 6 mm for Gew and 12 mm for Gns. Gns is less precise than Gew because no satellites fly over the North pole.In order to prepare the assimilation of the GPS observations via a Météo-France mesoscale data-assimilation system (ALADIN and AROME -- Météo-France's future operational model), GPS observations (ZTD, STD and gradients) simulators have been implemented in a non-hydrostatic high resolution model called Méso-NH. The digital laboratory, which the model Méso-NH constitutes, has been an effective means of quantifying the sensitivity of delays simulations at different formulations of atmospheric refractivity.La zone Cévennes-Vivarais et son extension jusque la Méditerranée a été choisie par l'OHM-CV (Observatoire Hydrométéorologique-Méditerranéen des Cévennes-Vivarais) pour la fréquence et la représentativité des événements de pluies intenses qu'elle subit. Depuis 2002, des campagnes automnales de mesures GPS y sont menées dans le but d'améliorer notre connaissance du champ de vapeur d'eau troposphérique associé aux événements de pluie intense. Les observations GPS météorologiques sont les ZTD (délais troposphériques au zénith) et les gradients de délais. Exprimé par une composante Est-Ouest (Gew) et une composante Nord-Sud (Gns), le gradient de délai traduit l'anisotropie du champ de vapeur d'eau à proximité du site GPS.Pour le traitement des observations GPS des réseaux permanents et temporaires de la région de l'OHM-CV, une configuration optimale a été recherchée à partir de différents tests de sensibilité. Une précision de 5 mm sur les ZTD peut être obtenue avec cette stratégie d'analyse pour le réseau régional GPS de la région de l'OHM-CV ; Gew est précis à 6 mm près, alors que Gns apparaît moins précis (à 12 mm près) du fait de l'absence de satellite survolant le pôle Nord.Afin de préparer l'assimilation des observations GPS par les systèmes d'assimilation de données à méso-échelle de Météo-France (modèle de Météo-France AROME), des simulateurs d'observations GPS (ZTD, STD et gradients) ont été implémentés dans le modèle non-hydrostatique à haute résolution Méso-NH. Le laboratoire numérique que constitue le modèle Méso-NH a été un moyen efficace de quantifier la sensibilité des simulations de délais à différentes formulations de la réfractivité atmosphérique

Potentiel de la mesure GPS sol pour l'étude des pluies intenses méditerranéennes

La zone Cévennes-Vivarais et son extension jusque la Méditerranée a été choisie par l'OHM-CV (Observatoire Hydrométéorologique-Méditerranéen des Cévennes-Vivarais) pour la fréquence et la représentativité des événements de pluies intenses qu'elle subit. Depuis 2002, des campagnes automnales de mesures GPS y sont menées dans le but d'améliorer notre connaissance du champ de vapeur d'eau troposphérique associé aux événements de pluie intense. Les observations GPS météorologiques sont les ZTD (délais troposphériques au zénith) et les gradients de délais. Exprimé par une composante Est-Ouest (Gew) et une composante Nord-Sud (Gns), le gradient de délai traduit l'anisotropie du champ de vapeur d'eau à proximité du site GPS.Pour le traitement des observations GPS des réseaux permanents et temporaires de la région de l'OHM-CV, une configuration optimale a été recherchée à partir de différents tests de sensibilité. Une précision de 5 mm sur les ZTD peut être obtenue avec cette stratégie d'analyse pour le réseau régional GPS de la région de l'OHM-CV ; Gew est précis à 6 mm près, alors que Gns apparaît moins précis (à 12 mm près) du fait de l'absence de satellite survolant le pôle Nord.Afin de préparer l'assimilation des observations GPS par les systèmes d'assimilation de données à méso-échelle de Météo-France (modèle de Météo-France AROME), des simulateurs d'observations GPS (ZTD, STD et gradients) ont été implémentés dans le modèle non-hydrostatique à haute résolution Méso-NH. Le laboratoire numérique que constitue le modèle Méso-NH a été un moyen efficace de quantifier la sensibilité des simulations de délais à différentes formulations de la réfractivité atmosphérique.GRENOBLE1-BU Sciences (384212103) / SudocSTRASBOURG-EOST (674822249) / SudocSudocFranceF