Airborne measurements of rain and the ocean surface backscatter response at C- and Ku-band

Abstract

During the 2002, 2003, and 2004 Hurricane seasons, and the 2005 Ocean Winds and Rain Winter Experiment, the University of Massachusetts (UMass) installed two instruments on the NOAA N42RF WP-3D research aircraft: the Imaging Wind and Rain Airborne Profiler (IWRAP) and the Simultaneous Frequency Microwave Radiometer (SFMR). IWRAP is a dual-band (C- and Ku), dual-polarized pencil-beam airborne radar that profiles the volume backscatter and Doppler velocity from rain and that also measures the ocean backscatter response. It simultaneously profiles along four separate incidence angles while conically scanning at 60 RPM. SFMR is a C-band nadir viewing radiometer that measures the emission from the ocean surface and intervening atmosphere simultaneously at six frequencies. It is designed to obtain the surface wind speed and the column average rain rate. Both instruments have previously been flown during hurricane seasons 2002, 2003 and 2004. Spectral techniques can been used to differentiate the contributions of the volume backscatter from rain from the ocean surface backscatter. Initial results from the Winter 2005 datasets are presented. Attenuation from rain is also particularly important at high microwave frequencies such as Ku-band. Thanks to IWRAP's profiling capabilities, Ku-band attenuation models and dropsize distribution (DSD) parameters of the observed precipitation from dual-wavelength techniques within tropical cyclones are presented.