Satellite passive microwave measurements are of interest for improving our understanding of cloud structures and for estimating precipitation over the globe. One type of retrieval algorithm estimates precipitation profiles based on cloud-radiation databases. However, many meteorological field experiments have indicated natural variations in microphysical parameters. Deficiencies or uncertainties in the knowledge and treatment of explicit microphysics schemes within mesoscale or cloud models will lead to errors and uncertainties in model precipitation then into calculated radiance and retrieved rain rate and vertical hydrometeor profiles. The main purpose of the study is to establish suitable ranges of cloud-processes related parameters, and to systematically evaluate the impacts of those parameters on simulated precipitation structures and microwave radiance.

The Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) mesoscale model (MM5) is utilized to quantify the influences of changes in microphysical parameters on the simulated surface rain rate, integrated hydrometeor content, water vapor and temperature fields. Two simulations of mid-latitude cyclones over the ocean have been performed. The corresponding satellite microwave images generated by a 3-D Monte Carlo model are compared with actual satellite measurements. The simulated images of clouds and rain bands have similar patterns to the observations. However, calculated brightness temperatures are not quite consistent with observed values in magnitude, and they are sensitive to the microphysical assumptions. These results indicate deficiencies both in the hydrometeor distributions produced by MM5 and in the default assumptions utilized in radiative transfer calculations.