This effort will improve surface precipitation rate and hydrometeor path retrieval methods appropriate for present and future passive millimeter-wave spectral imagers on NASA research and NOAA operational satellites. The four elements of the effort involve improvements in: 1) millimeter-wave radiative transfer models (RTM), 2) snow and graupel production rates in a cloud-resolving numerical weather prediction (NWP) model based on MM5, 3) retrieval methods for surface precipitation rates and water paths for various hydrometeor species, and 4) methods for assimilating millimeter-wave radiances into MM5 that improve precipitation and hydrometeor water path retrievals and forecasts, particularly for hurricanes.
The frequency range of interest, 23-425 GHz, is relevant to launched or proposed satellite instruments such as the Advanced Microwave Sounding Unit (AMSU), ATMS, SSM/IS, CMIS, SSM/I, TRMM, GPM, potential geostationary microwave sounders, and others. The physical model improvements will be followed by tuning that minimizes the differences between model predictions and coincident observations 23-191 GHz by AMSU on the NOAA-15, -16, and -17 satellites, and on the NASA Aqua satellite (AMSU/HSB). The retrieval methods will be optimized by minimizing the differences between the retrievals and improved MM5/RTM models (assumed ground truth) for over 100 global storms. The resulting retrieval methods will be evaluated by comparison with nearly coincident NEXRAD, SSM/I, and TRMM observations, and with MM5 simulations. These retrieval methods will also be evaluated for proposed geostationary microwave instruments employing filled-aperture antennas and aperture synthesis techniques.
To further improve precipitation-rate retrieval and assimilation methods, simulated microwave spectral images of precipitation will be used to perturb MM5 at various earlier times so that the resulting MM5 predicted radiances approximate those same observations. Such experimental methods will be validated using real data, as will NWP predictions based on such assimilations. Progress has been made in all areas by Prof. Staelin and his students. The proposed work is directly relevant to the NASA NRA, Appendix A.8 in the area "Precipitation Science" under Category 1.2: Retrieval algorithms, validation, and multi-satellite precipitation analysis, and Category 1.4: Improvements in weather forecast capabilities.
