Properties of light stratiform rain derived from 10‐ and 94‐GHz airborne Doppler radars measurements

Abstract

This paper presents an initial investigation of using airborne Doppler radar operating at 10 and 94 GHz to measure the light stratiform rain (≤5 mm hr−1). It has been shown that the combination of 10 and 94 GHz is more sensitive to resolve the raindrop size distribution (RSD) in light rain than that of 14 and 35 GHz. A case of light stratiform rain over southern Florida is examined in detail in this study. Techniques for retrieving the profiles of a Gamma raindrop size distribution (RSD), vertical air velocity, and attenuation by precipitation and water vapor are presented. This approach uses the difference of the Doppler velocity at two frequencies and yields both RSD and the vertical air motion. The approach is primarily applicable to rain rates less than 5 mm hr−1. The magnitudes of the retrieved RSD are similar to those found in ground‐based observations of light stratiform rain. The retrieved vertical winds with downdrafts below about 3 km and weak updraft above are similar to what has been observed in widespread stratiform rain with melting band. The sensitivities of the retrieval to Gamma shape parameter are discussed.