Evaluation of TRMM PR attenuation correction using ground radar estimations of the raindrop size distribution along the PR beam

Estimation of the raindrop size distribution (RSD) is made along the beam-path of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The PR is a nadir-pointing spaceborne radar that operates at 13.8 GHZ frequency. It is currently being used, along with other instruments aboard the TRMM satellite, for meteorological research. Short wavelength systems are used to reduce cost while maintaining the resolution near the Earth´s surface required for meteorological sampling. The limitations are the high signal degradation of the return signal caused by scattering and absorption of the precipitating medium that it is intended to probe. Correction of the TRMM PR return echo is based on a single-frequency technique, which is evaluated using ground-based polarimetric radar observations. Quantitative estimation of a 3-parameter gamma model is made of the RSD along the PR beam. PR attenuation correction is compared to the median values of the RSD parameters. In particular, variations of the median drop size diameter (DO) and normalized intercept parameter (N_w) with PR correction is made along the PR vertical profile in the rain layer. Data collected during the TExas and FLorida UNderflights (TEFLUN-B) experiment and TRMM Large Biosphere-Atmosphere experiment in Amazonia (LBA) field campaign is used in the evaluation.