Preliminary results of the validation of MERIS water vapour in the central Italy

In the framework of the ENVISAT project, we present the preliminary results of a validation campaign concerning atmospheric water, performed by means of a geographical network of ground-based sensors including multichannel microwave radiometers, GPS receivers, radiosondes, ground-based meteo stations, and the outputs of a mesoscale numerical prediction model (MM5). Comparison and cross-validation of the ENVISAT atmospheric water vapour with the values retrieved from microwave space-borne remote sensing instruments, such as SSM/I on board DMSP platforms, is also considered. The area of interest to our work is the central part of Italy, including the Tyrrhenian Sea. The test sites in our geographical network of instruments comprise the Elba Island (with a dual channel microwave radiometer, a GPS receiver and a meteo station), Perugia (with a GPS receiver and a meteo station), LAquila (with a GPS receiver and a meteo station), Pomezia (with a three channel microwave radiometer, and a radiosonde launching station). We present local comparisons of MERIS water performed at each test site considering the available ground-based instrumentation and the outputs of the MM5 model. In addition, we make extended area comparisons between MERIS water vapour maps and the corresponding maps obtained by the integration, within a geostatistical interpolation scheme, of ground-based instrument and SSM/I estimates of water vapour.