Analysis of Rainfall and Flood Signatures on X-Band Synthetic Aperture Radar Observations

The high resolution of Spaceborne Synthetic Aperture Radar (SAR) operating at X-Band might provide new insights into the structure of precipitating clouds and allow accurate observations also in remote or orographic areas where other measurements are not available. In this respect X-SAR capabilities have been report by several authors both by data [1]-[5] and model [6] analysis. Indeed, the exploitation of XSAR observations for quantitative precipitation retrieval is still at an early stage, while the traditionally reduced dutycycle of X-SAR spaceborne sensors has been nowadays partially resolved by the recently deployed COSMOSkyMed (CSK) and TanDEM-X/TerraSAR-X (TSX) constellations. On the contrary the use of X-SAR data to monitoring flooded areas is better established but the discrimination among permanent water bodies, flooded areas and areas affected by significant rainfall is not easy and may need to use ancillary data, as well as a certain amount of supervision, especially in orographic areas [1]. This paper presents a severe precipitation weather event, occurred in northwestern Italy (close to Liguria region) on November 3-8, 2011and monitored by using a number of CSK images provided by the Italian Space Agency (ASI) within the framework of the OPERA project. A new methodology has been applied to detect either permanent water bodies or flooded areas, as well as areas in which significant rain is present [7]. Over rain areas a new rainfall retrieval method will be applied, where X-SAR rainfall response is estimated using ancillary data, such as land cover maps and a digital elevation model (DEM), in order to enhance the X-SAR sensitivity to light rainfall.