Bright Band Characteristics Derived from Airborne Radar Measurements

One important aspect of TRMM validation is to characterize the reflectivity profile of the stratiform precipitation in which the presence of the bright band is the main feature. The study is aimed at providing insight on the microphysical process in the bright band and to provide valuable information for TRMM validation. During TRMM field campaigns, airborne radars operated on the DC-8 (2.1 cm wavelength) and the ER-2 (3.2 cm wavelength) provided high-resolution measurements of reflectivity, Doppler velocity and linear depolarization ratio from stratiform clouds. The preliminary analysis of five cases from Florida and Brazil show 1) Peak reflectivity in the bright band is larger than 40 dB in all cases except Brazil case. 2) The bright band thickness varies but rarely exceeds 200 meters. 3) Below the bright band, decrease of reflectivity and Doppler velocity with decreasing height suggest evaporation and breakup. The maximum velocity occurs 1 km below bright band suggesting the presence of partially melting particles. 4) In the snow/ice region above bright band, there is a small variation in fall speed and large variation the reflectivity. In this paper, we will present an analysis of profiles of these quantities through the bright band from both radars. These profiles will be compared with vertical profiles derived from ground-based radar measurements for some of the cases. The bright band model will be used to interpret observed profiles.