THE GPM SATELLITE HAS USHERED IN A NEW ERA OF GLOBAL RAINFALL ESTIMATION AS IT PROVIDES A MORE GLOBAL VIEW OF PRECIPITATION COMPARED TO TRMM RESULTING IN A WIDER VARIETY OF PRECIPITATION REGIMES FROM LIGHT RAIN TO INTENSE MIXED-PHASE MID-LATITUDE CONVECTION AND SNOW. THE PROPOSED RESEARCH IS CENTERED ON THREE MAJOR OBJECTIVES WHICH SEEK FUNDAMENTAL UNDERSTANDING OF STORM PROCESSES INCLUDING THE LIFECYCLE AND STRUCTURAL CHARACTERISTICS OF EXTRATROPICAL CYCLONES (ETCS) COMPARING THE NATURE OF CONVECTION IN GPM DUALPRECIPITATION RADAR (DPR) OBSERVATIONS AND HIGH-RESOLUTION CONVECTION-PERMITTING OPERATIONAL AND REGIONAL CLIMATE MODEL SIMULATIONS AND EVALUATING PRECIPITATION ESTIMATION IN EXTREME RAINFALL OVER THE OCEAN AND COMPLEX TERRAIN THE LATTER LEVERAGING A UNIQUE DATASET ON HEAVY RAIN. IN OBJECTIVE A WE WILL VALIDATE AND BETTER UNDERSTAND THE PERFORMANCE OF GPM ALGORITHMS (GMI IMERG DPR) IN REGIONS EXPERIENCING HEAVY RAINFALL OVER LAND OCEAN AND COMPLEX TERRAIN REGIONS USING DATA FROM RECENT AND PLANNED FIELD CAMPAIGNS. UNDERESTIMATES OF GPM DPR COMPARED TO GROUND OBSERVATIONS IN THE HEAVIEST RAINFALL OVER BOTH OCEAN AND LAND REGIONS OF THE WESTERN PACIFIC INDICATE THAT MORE RESEARCH IS NEEDED TO UNDERSTAND THE BIAS IN ESPECIALLY HEAVY RAINFALL LEADING TO IMPROVED SATELLITE ESTIMATES GLOBALLY. UNDER THIS OBJECTIVE WE WILL EVALUATE IMERG AND DPR RAIN ESTIMATES USING THE PRECIP FIELD CAMPAIGN DATASET TO BE OBTAINED IN SUMMER 2022 AND PRIOR FIELD CAMPAIGN DATASETS OF THE WESTERN AND EASTERN PACIFIC OCEANIC REGIONS FROM THE PISTON AND SPURS CAMPAIGNS RESPECTIVELY. OBJECTIVE B WILL BUILD ON OUR PREVIOUS WORK BY CONTINUING OUR INVESTIGATION OF THE THREE-DIMENSIONAL CHARACTERISTICS AND LIFE CYCLE OF ETCS IN THE NORTHERN AND SOUTHERN HEMISPHERES USING GPM DPR AND IMERG DATASETS. PARTICULAR ATTENTION WILL BE GIVEN TO ETCS OVER STORM TRACKS (INCLUDING OVER LAND) THE SOUTHERN OCEAN ETCS ASSOCIATED WITH ATMOSPHERIC RIVERS AND LAND FALLING ETCS. WE WILL EVALUATE SPECIFIC ETC CASES THAT OCCURRED DURING THE OLYMPEX FIELD CAMPAIGN TO EXAMINE RAIN VS. SNOW ESTIMATION IN COMPLEX TERRAIN LEVERAGING GROUND-BASED DISDROMETER AND POLARIMETRIC AND MULTIWAVELENGTH RADAR OBSERVATIONS. FINALLY OBJECTIVE C IS AN INVESTIGATION OF THE GLOBAL POPULATION OF PRECIPITATION SYSTEMS USING BOTH GPM DPR AND HIGH-RESOLUTION CONVECTION-PERMITTING REGIONAL CLIMATE SIMULATIONS TO PROVIDE IMPROVED UNDERSTANDING OF THE GLOBAL WATER CYCLE AND REPRESENTATION OF CLOUDS AND PRECIPITATION IN CURRENT CLIMATE SIMULATIONS. WE WILL CATEGORIZE DIFFERENT LIFECYCLE STAGES OF PRECIPITATING SYSTEMS USING BOTH GPM DPR AND SIMULATED REFLECTIVITY MODEL OUTPUT TO DETERMINE HOW WELL CONVECTION-PERMITTING CLIMATE SIMULATIONS REPRESENT THE SPECTRUM OF PRECIPITATING SYSTEMS IN THE U.S. AND SOUTH AMERICA. OUR RESEARCH WILL PROVIDE IMPORTANT INSIGHTS THAT WILL IMPROVE UNDERSTANDING OF THE VARIABILITY OF THE THREE-DIMENSIONAL CHARACTERISTICS OF GLOBAL PRECIPITATING SYSTEMS VALIDATE SATELLITE RETRIEVALS OF PRECIPITATION OVER COMPLEX TERRAIN AND OCEANS AND EVALUATE HOW WELL CONVECTION-PERMITTING NWP AND REGIONAL CLIMATE MODELS REPRODUCE THE STORM STRUCTURES VIEWED BY GPM. IMPROVING UNDERSTANDING OF THE GLOBAL NATURE OF CLOUDS AND HIGH-IMPACT WEATHER IS THE PRIMARY MOTIVATION BEHIND THE PROPOSED WORK AND THUS THIS RESEARCH IS A KEY FOCUS OF NASA S EARTH SCIENCE RESEARCH PROGRAM. THE PROPOSED RESEARCH DIRECTLY ADDRESSES 4 OUT OF 5 OF THE GPM SCIENCE OBJECTIVES. THE PROPOSED RESEARCH OBJECTIVES PRIMARILY ADDRESS PMM SOLICITATION RESEARCH CATEGORY 2.2 BY USING SATELLITE AND FIELD CAMPAIGN DATA TO STUDY PRECIPITATION AND MICROPHYSICAL PROCESSES BUT ALSO CONTRIBUTE TO CATEGORY 2.1.