THE SUITE OF CURRENT GLOBAL PRECIPITATION CLIMATOLOGY PROJECT (GPCP) PRECIPITATION PRODUCTS BASED ON GLOBAL OBSERVATIONAL DATA HAS BECOME A SCIENCE COMMUNITY STANDARD HAVING BEEN USED IN OVER 3500 JOURNAL ARTICLES. THE CURRENT MONTHLY (1979-PRESENT) AND DAILY (1996-PRESENT) PRODUCTS HAVE BEEN DEVELOPED BY RESEARCH GROUPS OVER THE LAST 20 YEARS. THE GPCP IS THE PRECIPITATION COMPONENT OF AN INTERNATIONALLY COORDINATED SET OF (MAINLY) SATELLITE-BASED GLOBAL PRODUCTS DEALING WITH THE EARTH S WATER AND ENERGY CYCLES UNDER THE AUSPICES OF THE GEWEX OF THE WCRP. WE PROPOSE TO USE THE STRENGTHS OFFERED BY RECENT SPACE-BORNE SENSORS AND RETRIEVAL METHODS TO GENERATE THE NEXT GENERATION GPCP MERGED PRECIPITATION PRODUCTS IN HIGH LATITUDES (GPCP V3.HL) POLEWARD OF 40O LATITUDE AND INTEGRATE IT TO THE LATEST GPCP PRODUCT. REVISING GPCP DATA PRODUCTS OVER SUCH CLIMATE-SENSITIVE AND HYDROLOGICALLY IMPORTANT REGIONS HAS REMAINED A MAJOR GAP BECAUSE IN HIGH LATITUDES (1) GPCP UNCERTAINTIES ARE THE HIGHEST (ADLER ET AL. 2012) AND (2) GPCP HAS NOT GONE THROUGH ANY MAJOR UPDATE OVER THE LAST 20 YEARS. THE PROPOSED WORK WILL IMPROVE GPCP IN HIGH LATITUDES BASED ON THE EMERGENCE OF ADVANCED NASA SENSORS IMPROVED RETRIEVAL TECHNIQUES INTERNATIONAL EFFORTS ON PRECIPITATION MEASUREMENT IN HIGH LATITUDES AND ADVANCES IN NUMERICAL MODELING. WE WILL IDENTIFY QUANTIFY DIAGNOSE AND REDUCE UNCERTAINTIES IN THE GPCP DATA PRODUCTS IN HIGH LATITUDES AND GENERATE AN IMPROVED LONG-TERM GPCP DATA RECORD CALIBRATED TO THE RECENT OBSERVATIONS FROM NASA S MISSIONS AND IN-SITU OBSERVATIONS FROM INTERNATIONAL GROUPS. CONNECTING THESE NEW SHORT-TERM MEASUREMENTS TO THE LONG-TERM GPCP ANALYSIS WILL AMPLIFY THE IMPACT OF NASA S NEW MISSIONS. THE PROPOSED WORK WILL USE VARIOUS EMERGING CAPABILITIES TO REVISE THE GPCP DATA PRODUCTS IN HIGH LATITUDES. THESE INCLUDE BUT ARE NOT LIMITED TO: (1) RAINFALL AND SNOWFALL DATA FROM NASA CLOUDSAT MISSION (2006-PRESENT) (2) SNOW ACCUMULATIONS THROUGH MASS BALANCE ANALYSES BASED ON NASA GRACE MISSION (2003-PRESENT) (3) ADVANCES IN HIGH LATITUDE PRECIPITATION ESTIMATION DRIVEN BY THE NASA GPM MISSION (4) RECENT INTERNATIONAL PROJECTS THAT ENHANCED SNOWFALL OBSERVATIONS AND BIAS CORRECTION FOR GAUGES (5) RECENT OCEANIC SHIPBOARD PRECIPITATION OBSERVATIONS (OCEANRAIN) RECORD FOR SURFACE VALIDATION AND (6) NEW GENERATION OF REANALYSIS (E.G. NASA MERRA2) AND HIGH RESOLUTION REGIONAL MODELS (I.E. ROCMO2). THE PROPOSED WORK WILL INVOLVE A MAJOR SHIFT TO NEW DATA STREAMS MODERN LEVEL 2 ALGORITHMS ADVANCED MERGER TECHNIQUES AND FINER TIME AND SPACE RESOLUTIONS. WE WILL COMPLEMENT THE LATEST VERSION OF GPCP (V3) CURRENTLY BEING FINALIZED (UNDER PREVIOUS MEASURES PI: HUFFMAN) THAT FOCUSES ON IMPROVEMENT OF GPCP OVER LOW AND MIDDLE LATITUDES USING TRMM AND GPM DATA. WE WILL ALSO BUILD ON THE METHODS DEVELOPED UNDER OTHER MEASURES EFFORTS (E.G. PI: ADLER) PROVIDING ERROR ESTIMATES FOR PRECIPITATION PRODUCTS AT MONTHLY TO DAILY TIME SCALES SO THAT THE REVISED GPCP PRODUCTS WILL HAVE BIAS AND RANDOM ERROR ESTIMATES WITH UNPRECEDENTED ACCURACY. THE PROPOSED WORK WILL PRODUCE IMPROVED MONTHLY GPCP IN HIGH LATITUDES USING RECENT DATA SETS AND USE THE NEW CALIBRATIONS TO UPDATE THE ENTIRE GPCP RECORD (1979-PRESENT) AT 0.5 O X0.5O SPATIAL RESOLUTION CONSISTENT WITH GPCP V3. ACCORDINGLY DAILY PRODUCTS WILL BE IMPROVED THROUGH UPDATED LEVEL 2 PRODUCTS AND WILL BE ADJUSTED TO MONTHLY PRODUCTS USING THE STANDARD GPCP PROCEDURES. THEREFORE THE PROPOSED WORK WILL COMPLEMENT PREVIOUS MEASURES INVESTMENT SO THAT THE NEXT GENERATION OF GPCP WILL INCLUDE UPDATES ACROSS THE ENTIRE GLOBE. AS WELL WE WILL WORK TO PRODUCE AN ADDITIONAL COMBINED OBSERVATION-MODEL ANALYSIS. THE PROPOSAL TEAM INCLUDES KEY GPCP DEVELOPERS. THIS ENSURES THAT THE OUTCOME OF THIS STUDY WILL BE EFFECTIVELY INTEGRATED TO THE FINAL PRODUCT FOLLOWING THE REQUIREMENTS FOR THE LONG-TERM CDR.