The PM-1 AMSR land and ocean rainfall algorithms are being developed separately, but the final global rainfall algorithm will be unified such that both land and ocean instantaneous rainfall estimates will be produced using the Goddard Profiling Algorithm (GPROF). The GPROF produces instantaneous rainfall estimates from the weighted average of rainfall rates from different hydrometeor profiles created from a cloud model database. The profiles used for estimation are chosen so that the observed microwave radiances match those obtained from radiative transfer calculations with the cloud model output. For the unified PM-1 AMSR algorithm, different profile databases will be used over land and ocean.
The databases used in this algorithm are selected to satisfy specified objectives. The initial database is chosen from cloud model output cases that result in relationships between rainfall rate and brightness temperature similar to those of the current FNMOC operational SSM/I land rainfall algorithm (that was developed at NESDIS). This database is then modified based on considerations such as location, season, and convective/stratiform classification, with the objective of providing the most realistic set of candidate profiles for the given situation. The results of this study are applied to SSM/I, TMI, and AMSR algorithms (all in the GPROF framework), as the same cloud model output cases are used in calculations of microwave brightness temperatures for the different frequencies and resolutions of each of these three sensors.
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