A new hybrid surface reference method for the TRMM Precipitation Radar

This paper describes the new hybrid method adopted in the TRMM standard algorithm that estimates the vertical profiles of attenuation-corrected radar reflectivity factor and rainfall rate. The attenuation correction is based on a hybrid of the Hitschfeld-Bordan method and a surface reference method. The new hybrid algorithm assumes errors in both the surface reference and the measured rain echoes. The optimum attenuation correction factor is determined by maximizing the conditional probability of the path-integrated attenuation for a given surface reference and a measured reflectivity profile