Rapid advances have been made in the development of satellite-based microwave precipitation retrieval algorithms and the quality of the associated precipitation products primarily due to the preparation for and subsequent launch of NASA's Tropical Rainfall Measuring Mission (TRMM). Each precipitation product has its strengths and weaknesses based on the instrument or instruments used, ancillary physical retrievals used as inputs and finally the assumptions and methods in the retrieval algorithms themselves. Highlighting the strengths and weaknesses of these precipitation products not only directly benefits those involved in the specific retrieval algorithms but those using the products for applications and climate research as well. For future missions, such as the Global Precipitation Mission (GPM), this type of analysis will need to continue as new retrieval algorithms are proposed using new measurement capabilities. The Precipitation Processing System (PPS) is the data system that will generate the standard precipitation products for both Version 7 TRMM and precipitation missions in the GPM era. The role of the data system in the testing of retrieval algorithms, generation of standard products and quality control of both is clear. An additional capability of the data system is the generation of analysis products (zonals, time-series, statistical analyses, sensitivity tests, etc.) for the sole purpose of improving retrieval algorithms. The work proposed here goes beyond the mechanics of generating these various analysis products and is focused on the integration of the knowledge gained back into the retrieval algorithms through the Precipitation Measuring Missions (PMM) Science Team. Our group is in a unique position to assist in evaluating and improving precipitation retrieval algorithms, not only having been involved in the development and prototyping of PPS but having been involved with the TRMM data system and the developers of the retrieval algorithms since before launch.
