TRMM Validation Program

The Tropical Rainfall Measuring Mission (TRMM) Validation Program has established, participates in and supports a broad range of complementary activities, including instrument development, algorithm development, research on data assimilation techniques, modeling studies, field experiments and international cooperative arrangements, all aimed at providing the most accurate rainfall measurements possible at a number of representative sites around the tropics in order to validate estimates of rainfall from the space-borne instrument complement that will orbit Earth aboard the TRMM satellite. The Program also includes ground-based measurements of the vertical structure of precipitation systems, physical process and modeling studies to better understand the relation between vertical structure and latent heat release, development of airborne sensing technology for instantaneous validation and/or calibration of TRMM: over oceans, investigations of multiparameter radar techniques for improved accuracies, and determination of pre-mission climatologies for the refinement of sampling error analyses. The TRMM validation strategy also includes establishment of one or more world-class facilities for rain measurement research and calibration of both new and existing rainfall measuring instruments, including ocean techniques. Given the difficulties of measuring rain intensity because of its extreme variability in time and space, it is recognized that a consistent rain measurement/estimation scheme for calibrating and validating space measurements will necessarily involve a hybrid system of observations that, with appropriate climatologically-dependent algorithms and analysis schemes, will ensure data of uniform quality and reliability