Rainy events detection by means of observed brightness temperature ratio

This paper presents the results of a study aiming at detecting rainy data in measurements collected by a dual band ground-based microwave radiometer. The proposed criterion is based on the sky status indicator (SSI) derived from brightness temperatures observed in the 20-30 GHz band without need of any ancillary information. A major result obtained from the CDF of almost three months of data is the identification of threshold values of SSI between clear sky, cloudy sky and rainy sky, respectively. As measurements were taken at elevation angle equal to 90°, these values need to be confirmed. Nevertheless, the threshold values between clear/cloudy sky (SSI equal to 0.5) and cloudy/rainy sky (SSI equal to 0.9) are in agreement with previous pilot experiments.