Improving the instantaneous vertical profiling of precipitation from spaceborne radiometers using high sensitivity ground based radar measurements

The main element that is missing from current passive-microwave retrievals that are based on the a-priori knowledge provided by simultaneous radar and radiometer measurements, as provided by the TRMM radar and radiometer, is the quantitative description of the vertical distribution of the precipitation. Indeed, the TRMM radar being a single-channel instrument, it cannot by itself identify the phase of the condensation. In addition, its detection threshold is high enough to make it insensitive to the solid condensation that overlies much of the precipitation that occurs in the tropics. During to the CINDY-DYNAMO experiment that took place in 2011-2012, the dual-wavelength polarimetric radar SPolKa was deployed, providing a unique set of observations. Three complementary measurements are available: the Zdr, and the S- and Ka-band reflectivities. This allows insight into rainfall characteristics for different species. Using cloud-resolving simulations, different moments of the Drop Size Distribution such as the rainfall rate, the cloud liquid water, or the mean diameter can be retrieved from SPolKa data. Different assumptions (on hydrometeor habit and size distributions) for those simulations were used, and their impact on the retrievals evaluated. Also, brightness temperatures were simulated for different assumptions on the DSD and compared to TRMM overpasses. This sensitivity analysis study will allow the elaboration of a new database for passive microwave algorithms, accounting for the quantitative vertical distribution of precipitation.