Rainfall estimation by combining radar and infrared satellite data for nowcasting purposes

The aim is to evaluate the use of infrared satellite precipitation estimate s for nowcasting purposes in the context of a real-time flood-warning schem e. A radar-based calibration technique is described which is applied to the Negri-Adler-Wetzel scheme. This procedure employs radar data over a define d calibration area to estimate, for each satellite image, actual min-rates to be used in the Negri-Adler-Wetzel scheme. Calibrated satellite estimates obtained from this procedure can be used to diagnose areas of precipitatio n beyond radar range, thus allowing an extension of precipitation nowcastin g lead time. Calibrated estimates are compared with radar rainfall measurem ents and results are discussed for various sizes of integration area. Calib ration reduces consistently both bias and variance of the error of the orig inal Negri-Adler-Wetzel estimates, even for integration areas as small as 2 000 km(2). This indicates the capabilities of the new technique for nowcast ing purposes over medium-sized river basins.