Contributors: Laboratoire de l'Atmosphère et des Cyclones (LACy); Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Météo-France; Observatoire Volcanologique du Piton de la Fournaise (OVPF); Institut de Physique du Globe de Paris (IPG Paris); Institut de Physique du Globe de Paris (IPGP (UMR_7154)); Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité); Institut National de l'Information Géographique et Forestière IGN (IGN); Seychelles Islands Foundation (SIF); Institut supérieur de technologie d'Antsiranana; The GNSS stations of DSUA, MASM, MATA, MAFD, and ALBR were deployed in the frame of INTERREG-5 Indian Ocean 2014–2020 research project “ReNovRisk Cyclones and Climate Change,” funded by the European Union, La Reunion Regional Council and the French Government. GNSS stations of EURP, JDNV, GLOR, and TROM were installed as part of research project “IOGA4MET-EI,” funded by the research consortium “Iles Eparses” 2017–2020, while NOSY was funded by La Reunion University through its internal research program OMNCG. IGN was funded by CNRS to coordinate geodetic operations for the Mayotte seismic-volcanic crisis. Since the implementation of this ground-based GNSS Observation Network in the Southwest Indian Ocean, the stations GLOR, DSUA, and NOSY are now included in the monitoring of the Mayotte volcano activity through the REVOSIMA (Réseau de surveillance volcanologique et sismologique de Mayotte). REVOSIMA also participated in the funding of the densification of the GNSS network in the Mayotte area.
نبذة مختصرة : International audience ; In the frame of the research project IOGA4MET, a new ground-based GNSS network is being deployed in the Southwest Indian Ocean (SWIO) since November 2017. This new network opens up for new research opportunities in geodesics and atmospheric sciences in this area regularly exposed to natural hazards, and significantly expands the International GNSS System (IGS) network, which only includes eight stations so far in the SWIO. After a description of the current status of IOGA4MET, several examples of regional applications in meteorology (climatology and numerical modeling) and geodesy (monitoring of ground deformations) are presented using data collected in northern Madagascar and small neighboring islands in 2018–2020. The observed water vapor cycle is shown to exhibit different characteristics and important variability at all locations. At the seasonal scale, maximum IWV values are similar everywhere, minimum values decrease away from the equator and a sharp IWV gradient can be noticed during the wet–dry transition period. At this time scale, the seasonal IWV cycle analyzed with the high-resolution NWP system AROME-IO matches observations with little discrepancies. At the diurnal scale, IWV characteristics show different behavior on each side of Madagascar, which emphasizes the important role of this island in driving the regional circulation. Finally, examination of ground displacements measured by GNSS stations in relationship with the ongoing Mayotte seismic-volcanic crisis indicates that ground deformation associated with the current off-shore volcanic activity east of Mayotte does not extend up to 250 km, or is currently too low to be detected in very far field.
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