THE OVERARCHING GOAL OF THIS RESEARCH PROJECT IS TO LEVERAGE MULTI-RADAR/MULTI-SENSOR (MRMS) QUANTITATIVE PRECIPITATION APPLICATIONS TO GPM TO SYNERGIZE CONUS-WIDE GROUND VALIDATION AND TRMM/GPM ALGORITHM ENHANCEMENT. THE FOCUS IS ON PRECIPITATION MICROPHYSICS AND UNCERTAINTY CHARACTERIZATION BY TAKING ADVANTAGE OF THE MRMS MULTI-SCALE SURFACE PRECIPITATION INFORMATION AND THE GPM VALIDATION NETWORK (VN) TO BRIDGE 2-D SURFACE WITH 3-D PRECIPITATION STRUCTURES FOR IMPROVED UNDERSTANDING OF PRECIPITATION PROCESSES AND THEIR PARAMETERIZATION IN GPM RETRIEVAL ALGORITHMS. ULTIMATELY THE RESEARCH SEEKS TO IMPROVE GPM RETRIEVAL ALGORITHMS FOR BOTH LEVEL-2 AND LEVEL-3 AND CHARACTERIZE THE UNCERTAINTY OF THE PRECIPITATION PRODUCTS. TASKS ARE: 1.PERFORM AN IN-DEPTH COMPARISON ANALYSIS BETWEEN SPACE RADARS TRMM-PR/GPM-DPR/COMBINED DPR+GMI (GCI) AND MRMSGPM UNDER VARIOUS REGIMES OF PERFORMANCE. COMPLEMENTARY INSIGHT WILL BE EXTRACTED BY CONDITIONING THE ANALYSIS BY RESPECTIVE MRMS-BASED AND GPM-BASED ALGORITHM ASSUMPTIONS AND METHODS. COMPARISON OF 3-D PRECIPITATION STRUCTURES MICROPHYSICAL PROPERTIES AND PARAMETERIZATIONS (HYDROMETEOR TYPES AND PHASE PARTICLE SIZE DISTRIBUTION) AND SURFACE PRECIPITATION BETWEEN GROUNDAND SPACE-BASED RETRIEVALS WILL IMPROVE UNDERSTANDING AND QUANTIFICATION OF PRECIPITATION PROCESSES OVER VARIOUS SURFACES (E.G. COMPLEX TERRAIN). WE WILL CHECK CONSISTENCY REGARDING PRECIPITATION DETECTABILITY ANALYZE THE IMPACT OF SMALL-SCALE VARIABILITY AND EVALUATE THE REFLECTIVITY ATTENUATION CORRECTION.