An algorithm for estimating rain rate by a dual‐frequency radar

This paper concerns an estimation algorithm of rain rates for a dual-frequency radar at rain-attenuating bands. The estimations are made based on the concept of least squares. In the algorithm, the ratios of received echo powers at adjacent range bins at each frequency are used to eliminate some unknown and/or undetermined factors, such as radar calibration factors. The algorithm, which is applicable when a part of echoes at one frequency is missing due to rain attenuation, is also developed. In the estimation algorithm, the relationship between specific attenuation and rain rate (k-R relationship), and that between effective Z factor and rain rate (Z-R relationship), are assumed to be expressed by the usual power law form. The k-R relationships are fixed; however, the Z-R relationships are expressed by the least squares regression form in terms of the measured quantities and the rain rates. The results of computer simulation experiments are described to demonstrate the validity of the present algorithm.