IN ORDER TO VALIDATE SATELLITE SEA SURFACE SALINITY (SSS) MEASUREMENTS ASSIMILATE SSS IN NUMERICAL MODELS AND USE SSS TO OBSERVE THE OCEAN COMPONENT OF THE GLOBAL HYDROLOGICAL CYCLE THE DYNAMICS AND SPATIO-TEMPORAL SCALES OF NEAR-SURFACE SALINITY STRATIFICATION NEED TO BE BETTER UNDERSTOOD. RAIN FRESHENS THE OCEAN LEADING TO A STRATIFIED SURFACE LAYER BUT MEASUREMENTS SUGGEST THAT MATHEMATICAL RELATIONSHIPS DERIVED TO EXPLAIN HOW RAIN AND WIND INFLUENCE SALINITY STRATIFICATION ARE DIFFERENT DEPENDING ON THE SPATIO-TEMPORAL RESOLUTION OF RAIN AND WIND DATA USED. THESE DIFFERENCES IMPLY THAT MORE OBSERVATIONAL RESEARCH IS NEEDED TO BETTER UNDERSTAND THE DEPENDENCE OF SALINITY STRATIFICATION ON THE HORIZONTAL AND TEMPORAL VARIABILITY OF RAIN AND WIND RANGING FROM IN SITU POINT MEASUREMENTS TO SATELLITE FOOTPRINT SCALES. BOTH RAIN AND WIND SPEED ARE KNOWN TO BE IMPORTANT FOR DETERMINING NEAR-SURFACE SALINITY STRATIFICATION; THE CENTRAL HYPOTHESIS OF THIS PROPOSAL IS THAT THAT THE RELATIONSHIP OF SALINITY STRATIFICATION TO RAIN AND WIND DEPENDS ON THEIR SPATIO-TEMPORAL SCALES. THE PROPOSED WORK IS MOTIVATED BY THREE CENTRAL QUESTIONS: (1) WHAT ARE THE MOST IMPORTANT RAIN METRICS FOR DETERMINING THE FORMATION STRENGTH LIFETIME AND HORIZONTAL EXTENT OF SALINITY STRATIFICATION AND HOW ARE THESE RELATIONSHIPS INFLUENCED BY WIND SPEED? (2) DO SATELLITE-BASED RAIN AND WIND MEASUREMENTS CAPTURE ENOUGH SPATIAL AND TEMPORAL VARIABILITY TO ADEQUATELY DESCRIBE THE PHYSICS ASSOCIATED WITH NEAR-SURFACE SALINITY STRATIFICATION? (3) IN WHAT REGIONS UNDER WHICH CONDITIONS AND AT WHICH SCALES IS SALINITY STRATIFICATION PREDICTABLE WITH SATELLITE-BASED RAIN AND WIND ESTIMATES? THESE QUESTIONS WILL BE ANSWERED BY COMPLETING THE FOLLOWING OBJECTIVES: (1) RELATE IN SITU MEASUREMENTS OF SALINITY STRATIFICATION FROM THE SPURS-2 EXPERIMENT TO THE SPATIAL AND TEMPORAL VARIABILITY OF RAINFALL AND WIND AS ESTIMATED BY SATELLITE METHODS AND AS MEASURED BY SPURS-2 IN SITU INSTRUMENTS INCLUDING AREA-EXTENSIVE RAIN MEASUREMENTS COLLECTED BY RAIN RADAR AND DISDROMETER. (2) QUANTIFY THE DIFFERENCES AND ANY BIASES BETWEEN THE CAPABILITIES OF SATELLITE VS. IN SITU RAIN AND WIND METRICS FOR PREDICTING IN SITU SALINITY STRATIFICATION VARIABILITY. (3) TEST SATELLITE-BASED PREDICTIONS OF SALINITY STRATIFICATION DEVELOPED IN OBJECTIVE 2 WITH ARGO SALINITIES AND SATELLITE-BASED RAIN WIND SPEED AND SURFACE SALINITY. BECAUSE SATELLITE INSTRUMENTS AND IN SITU OBSERVATIONS PROVIDE DIFFERENT VIEWS OF THE PROCESSES THAT GENERATE SURFACE FRESHENING IT IS IMPORTANT TO UNDERSTAND HOW THE SPATIAL AND TEMPORAL SCALES OF RAIN AND WIND ARE RELATED TO THE OBSERVED VARIABILITY IN NEAR SURFACE SALINITY. THE PROPOSED WORK WILL ADDRESS THIS ISSUE IN ORDER TO UNDERSTAND HOW DATASETS FOR RAIN AND WIND EACH WITH DIFFERENT MEASUREMENT SCALES CAN BE USED TO MODEL NEAR-SURFACE SALINITY STRATIFICATION. THIS PROPOSAL RESPONDS DIRECTLY TO THE FOURTH TOPIC OF THE NASA-ROSES 2017 OCEAN SALINITY SCIENCE TEAM SOLICITATION: "NEAR-SURFACE SALINITY STRATIFICATION (IN THE UPPER FEW METERS) AND THE UNDERLYING PHYSICAL PROCESSES CONTINUE TO NEED ATTENTION." THE PROPOSED WORK WILL DETERMINE THE MOST IMPORTANT SCALES AND METRICS OF RAIN AND WIND FOR DETERMINING IN SITU SALINITY STRATIFICATION. THIS WORK WILL ALSO ESTABLISH A MORE INFORMED BASELINE FOR USING SATELLITE RAIN AND WIND PRODUCTS TO MODEL OBSERVED SALINITY STRUCTURES. THE PROPOSED RESEARCH WILL ADVANCE THE SALINITY SCIENCE TEAM GOAL OF USING SATELLITE SSS ESTIMATES AS A "RAIN GAUGE" BY DETERMINING WHERE WHEN AND HOW SATELLITE RAIN AND WIND PRODUCTS CAN BE USED TO ESTIMATE VARIATIONS IN NEAR-SURFACE SALINITY STRUCTURE AS WELL AS BY DETERMINING THE CONDITIONS IN WHICH SALINITY STRATIFICATION REVEALS FRESHWATER IMPACTS NOT CAPTURED BY SATELLITE RAIN ESTIMATES.