Methodology to simulate GPM radar observations, from combined radiometer and radar measurements from TRMM and cloud models

The Global precipitation mission is conceptually centered on the deployment of a “core” satellite with an active dual-frequency (Ka/Ku band) precipitation radar, and microwave imager capable of sensing the total precipitation within all cloud layers (http://gpm.gsfc.nasa.gov). Compared to the single-frequency TRMM (Tropical Rainfall Measuring Mission) precipitation radar (PR), the dual-frequency precipitation radar (DPR) onboard GPM core satellite is expected to enhance our understanding on microphysics, and provide more accurate retrieval of rainfall and liquid water content. The goal of the present study is to combine the TMI (TRMM's Microwave Imager), TRMM PR and a mesoscale WRF (Weather Research and Forecast) model to simulate the DPR reflectivity profiles. Prior studies to simulate the DPR profiles were done based on TRMM PR observation using frequency scaling arguments and hydrometeor classification [1]. First, the methodology to retrieve self consistent hydrometeor profiles from a combination of TMI, PR observations as well as WRF model is described. Using the TRMM constrained WRF model profiles, a procedure to simulate DPR observations is described. Attenuation from cloud water and cloud ice is considered. Simulation of cyclone Nargis shows reasonable results using TMI retrieved microphysics. Attenuations from both precipitation and non-precipitation are also compared.