French-Italian X- and C-band dual-polarized radar network for monitoring South Alps catchments

In the framework of the CRISTAL (CRues par l'Integration des Systemes Transfrontaliers Alpins) project, two dual-polarized X-band radars have been deployed for monitoring the catchment of the Roya, located in the south Alps at the French-Italian border. The French radar (Hydrix) has been installed in the Maritime Alps (Mt-Vial, 1500 m) and the Italian radar was installed at Col de Tende at 1800 m altitude during the summer of 2010. Two Italian C-band dual-polarized radars complete the network, ensuring a full monitoring of the Roya catchment. This paper focuses on the capability of the two operational X-band radars to complement each other when monitoring rain/flood events in a mountainous area. Also illustrated is their ability for gap-filling neighbouring C-band radars which are blinded by orography. The ZPHI (R) algorithm is applied to the whole set of radar data, correcting for signal attenuation and estimating drop-size distribution and surface rainfall without any use of raingauge information. A case study from summer 2010 is shown, by comparing various radar-derived rainfall mosaics.