GPM Dual-frequency Precipitation Radar (DPR) and TRMM Precipitation Radar (PR) single-orbit rainfall estimates. The objective of these radar algorithms is to generate f radar-only derived meteorological quantities on an instantaneous FOV (field of view) basis working from the level 1 radar products. A subset of these estimates serves as input data to the level 2 combined radar-radiometer algorithm and the level 3 combined and radar-only products. The general idea behind these level 2 algorithms is to determine general characteristics of the precipitation, correct for attenuation, and estimate profiles of the precipitation water content, rainfall rate. When dual-wavelength data are available, the algorithm also estimates the particle size distributions in the phase of the precipitation (i.e., liquid or frozen). GPM's dual-wavelength data will provide better estimates of rainfall and snowfall rates than those of the TRMM PR data.