THE CENTRAL OBJECTIVE OF THIS PROPOSAL IS TO USE ANALYSIS OF OBSERVATIONS AND HIGH RESOLUTION SIMULATIONS TO EXPLORE THE SEASONAL AND INTERANNUAL DYNAMICS OF THE FRESH AMAZON/ORINOCO PLUME AND ITS INTERACTIONS WITH THE CONTINENT AND SURROUNDING OCEAN. THE AMAZON/ORINOCO PLUME (REFERRED TO HEREAFTER AS THE AMAZON PLUME) IS A SHALLOW SEASONALLY VARYING TURBID LOW SALINITY WATER THAT SPANS AN AREA IN EXCESS OF 106 KM2 BY LATE SUMMER - EARLY FALL. IT HAS STRIKING FEATURES THAT MAKE IT AN APPEALING TARGET FOR APPLICATION OF THE REMOTE SENSING TOOLS MADE AVAILABLE BY NASA. IT IS THE WORLD S LARGEST FRESHWATER PLUME FORCED BY THE MASSIVE DISCHARGE FROM THE AMAZON AND ORINOCO RIVER SYSTEMS AND THUS LINKS AN ACTIVE CONTINENTAL HYDROLOGIC SYSTEM TO OCEANIC DYNAMICS. BESIDES THE TERRESTRIAL FRESHWATER DISCHARGE FORCING IT LIES IN A REGION OF SOME OF THE HIGHEST SEASONAL RAINFALL RATES ANYWHERE IN THE WORLD OCEAN. THE LARGE SPATIAL EXTENT OF THE PLUME ITS HIGH VALUES OF SST AND EVAPORATION AND LOW RATES OF VERTICAL HEAT EXCHANGE WITH THE COOLER AND SALTIER WATER BELOW PROMOTE INTERACTION WITH AND INTENSIFICATION OF FALL SEASON HURRICANES. AND MOST IMPORTANTLY THE PLUME LIES ON TOP OF THE VIGOROUS EDDY-SHEDDING NORTH BRAZIL CURRENT SYSTEM WHICH IS A KEY COMPONENT OF THE UPPER BRANCH OF THE ATLANTIC MERIDIONAL OVERTURNING CIRCULATION THAT CONNECTS THE AMAZON PLUME TO THE CARIBBEAN AND THE NORTH ATLANTIC. YET DESPITE ITS IMPORTANCE THIS IS ONE OF THE LESS-WELL STUDIED WESTERN BOUNDARY CURRENT SYSTEMS. WE PROPOSED TO EXAMINE THE PLUME DYNAMICS THROUGH A MULTI-SENSOR ANALYSIS AND A NUMERICAL SIMULATION STUDIES TO EXPLORE THE ROLE OF MESOSCALE OCEAN DYNAMICS IN THE WESTERN TROPICAL ATLANTIC. A GOAL WILL BE TO UNDERSTAND THE ROLE THAT NASA CONSTELLATION OF REMOTE SENSING TOOLS SUCH AS AQUARIUS AND SMAP WITH THEIR UNIQUE CAPABILITIES TO MAP SSS CAN PLAY IN EXAMINING RELATIVE ROLES OF THE OCEAN AND TERRESTRIAL ELEMENTS OF THIS SYSTEM. ALONG WITH OBSERVATION ANALYSES THIS PROPOSED RESEARCH WILL EMPLOY A NUMBER OF EXISTING AND PROCESS-TARGETED SIMULATIONS. THE EXISTING EDDY RESOLVING 1/12O POP2 OCEAN MODEL WITH 10M GRID SPACING IN THE UPPER 150M AND THE NEWEST SODA VERSION 3 WILL BE USED TO EXPLORE THE MIXED LAYER SALT BUDGET. PROCESS-TARGETED MODEL SIMULATIONS WILL EMPLOY A SERIES OF TWIN ROMS RUNS SPANNING THE PLUME-TO-CARIBBEAN REGION IN WHICH OBSERVED DISCHARGE AND ATMOSPHERIC FORCING ARE PERTURBED. BY ADDRESSING THE ABOVE SCIENTIFIC QUESTIONS WE FOLLOW THE BULLETS (1) AND (2) OF THE OSST/2016 CALL IN ORDER TO EXPLOIT THE NASA SATELLITE SSS MEASUREMENTS TO INVESTIGATE SSS VARIABILITY ITS INFLUENCE ON OCEAN CIRCULATION AND THE LINKAGE WITH CLIMATE AND WATER CYCLE. NASA SSS MEASUREMENTS WILL BE USED IN SYNERGY WITH OTHER SATELLITE AND IN SITU MEASUREMENTS (INCLUDING SALINITY MEASUREMENTS FROM SMOS AND ARGO AS WELL AS SATELLITE MEASUREMENTS OF OTHER OCEANIC PARAMETERS). BY USING CONTINUING RECORDS OF SMAP SSS WE WILL ALSO ADDRESS THE BULLET (3) BY INVESTIGATION THE VALUE OF SMAP DATA AND THEIR CONSISTENCY WITH ONGOING SMOS AND PREVIOUS AQUARIUS.