Validation of raindrop size distribution retrieval from spaceborne radar using ground polarimetric radar observations

The cumulative attenuation (A) along TRMM PR path given by the surface reference technique (SRT) can be distributed along the radar range using a power law relation between the specific attenuation (k) and reflectivity factor (z) written as, k=aZ^beta. A commonly used approximation is that beta is constant and alpha changes according to the raindrop size distribution (DSD). More recently physical interpretation of alpha has been provided with the normalized drop size distributions. This paper evaluates the method to estimate the DSD parameters from TRMM PR observations. Coincident data collected with polarimetric radar on the ground during the TRMM field campaigns was used to compare the estimates of DSD retrieved from TRMM PR. This paper also introduces a new methodology for comparing DSD estimates from widely varying sampling volumes. The cross validation shows fairly good agreement, thereby validating the DSD retrieval process