GPM HAS USHERED IN A NEW ERA OF GLOBAL RAINFALL ESTIMATION FOLLOWING THE HIGHLY SUCCESSFUL TRMM MISSION. GPM PROVIDES A MORE GLOBAL VIEW OF PRECIPITATION COMPARED TO TRMM RESULTING IN A WIDER VARIETY OF PRECIPITATION REGIMES FROM LIGHT RAIN TO INTENSE MIXEDPHASE MID-LATITUDE CONVECTION AND SNOW. GPM ALSO EMPLOYS MORE COMPLEX RAINFALL ALGORITHMS COMPARED TO TRMM. OUR PROPOSED RESEARCH IS CENTERED ON THREE MAJOR OBJECTIVES WHICH BROADLY SEEK TO IMPROVE GPM RAIN AND SNOWFALL ESTIMATION AS WELL AS CARRY OUT FUNDAMENTAL RESEARCH REGARDING EXTRATROPICAL CYCLONES A MAJOR CONTRIBUTOR TO EARTH S PRECIPITATION. IN OBJECTIVE A WE SEEK TO IMPROVE GPM RAINFALL ESTIMATION BY LINKING DROP SIZE DISTRIBUTION (DSD) STRUCTURES TO LARGE SCALE ENVIRONMENTAL VARIABLES. WE ARGUE THAT FOR A GIVEN LARGE SCALE ENVIRONMENT DESCRIBED BY CAPE SHEAR ETC. A CONSTRAINED SET OF DSDS ARE LINKED TO THAT PARTICULAR ENVIRONMENT. THIS DISTRIBUTION OF DSDS IMPLIES CONSTRAINTS ON Z-R RELATIONSHIPS USED TO ESTIMATE RAINFALL WHICH CAN BE LEVERAGED BY THE GPM RAINFALL ALGORITHM. WE SEEK TO EXTEND THIS METHODOLOGY TO PARTICLE SIZE DISTRIBUTIONS OF SNOW WHICH WILL PROVIDE IMPORTANT CONSTRAINTS FOR GPM SNOWFALL RETRIEVALS. IN OBJECTIVE B WE WILL WORK WITH OLYMPEX DATA TO EXAMINE GPM RAINFALL AND SNOWFALL ESTIMATION VALIDATING THESE ESTIMATES AGAINST GROUND-BASED OBSERVATIONS IN THE SETTING OF COMPLEX TERRAIN. FINALLY OBJECTIVE C WILL TAKE ADVANTAGE OF THE WIDE COVERAGE OF GPM TO STUDY THE STRUCTURE AND PRECIPITATION PHYSICS OF EXTRATROPICAL CYCLONES.