The role of both location and radiometer accuracy on the SSI performance in discriminating the atmospheric conditions

This study addresses the sensitivity of the Sky Status Indicator (SSI) with respect to both the radiometer accuracy and location of three stations included in the ground segment of the Alphasat experiment. The SSI aims at detecting the atmospheric conditions along a slant path, exploiting radiometric data at 20/30 GHz. The analysis is performed on synthetic brightness temperatures computed from a database of radiosonde profiles collected in De Bilt (NL), Milano (I), and Roma (I) through forward modelling. The SSI sensitivity to both radiometric resolution and bias error is computed for elevation angles equal to 27.6, 35.5, 40.2, 69.6, and 90°. Robustness of SSI boundary threshold values between clear and cloudy sky conditions is assessed.