THE INTERTROPICAL CONVERGENCE ZONE (ITCZ) EXTENDS ACROSS THE EASTERN AND CENTRAL PACIFIC FOR MORE THAN 6 000 KM. WHEN THE ITCZ MOVES SOUTHWARD DURING EL NI O HUGE INTERANNUAL FLUCTUATIONS IN RAINFALL OCCUR AND SEA SURFACE SALINITY (SSS) IS LOWERED FOR MORE THAN 6 000 KM FROM THE EQUATOR TO 5 DEGREES N. HOW EXACTLY DOES THE OCEAN RESPOND TO SUCH A HUGE FLUX OF FRESH WATER? WE PROPOSE TO ANALYZE THE PHYSICS OF THE OCEAN RESPONSE USING AQUARIUS AND SMAP SSS AND OTHER SATELLITE AND IN SITU OBSERVATIONS. OTHER SATELLITE OBSERVATIONS WILL INCLUDE ALTIMETER SEA SURFACE HEIGHT SEA SURFACE TEMPERATURE (SST) AND PRECIPITATION FROM THE INTEGRATED MULTISATELLITE RETRIEVALS FOR GLOBAL PRECIPITATION (IMERG); IN SITU DATA WILL COME FROM THE EQUATORIAL AND NEAR-EQUATORIAL TAO MOORED BUOY ARRAY ARGO FLOAT OBSERVATIONS AND BOTTOM PRESSURE FROM THE DEEP-OCEAN ASSESSMENT AND REPORTING OF TSUNAMIS (DART). SPECIFICALLY WE AIM TO ACHIEVE THE FOLLOWING GOALS (I) VERIFY OBSERVATIONALLY THAT THE INITIAL OCEAN RESPONSE TO FRESH WATER MASS FLUX IS SO RAPID THAT THE ADDITIONAL MASS SIGNAL AND ITS ASSOCIATED-BAROTROPIC PRESSURE ARE TYPICALLY NEGLIGIBLE WITHIN A FEW HOURS AFTER THE RAIN HAS FALLEN. (II) ESTIMATE THE SHALLOW NEAR-SURFACE SALINITY-INDUCED INTERANNUAL FLOWS IN THE EASTERN PACIFIC BETWEEN 12 DEGREES S AND 12 DEGREES N AND EAST OF 140 DEGREES W. THIS WILL INCLUDE A MORE DETAILED EXAMINATION OF A PREVIOUSLY UNIDENTIFIED VERY SHALLOW SALINITY-INDUCED INTERANNUAL FLOW STRETCHING FOR THOUSANDS OF KILOMETERS ACROSS THE EASTERN EQUATORIAL PACIFIC. (III) DETERMINE THE ORIGIN OF THE MONTHLY SALINITY ANOMALIES. (IV) DETERMINE THE INTERANNUAL NEAR-SURFACE FLOW S EL NI O PREDICTION CAPABILITY. (V) PROVIDE A CONTEXT FOR THE 1-YEAR SALINITY PROCESSES IN THE UPPER-OCEAN REGIONAL STUDY-2 (SPURS-2). THIS WILL INCLUDE AN ASSESSMENT OF THE DYNAMICAL EFFECT OF THE ANNUAL CYCLE AND INTERANNUAL VARIABILITY OF NEAR-SURFACE SALINITY ON THE SEA LEVEL AND SURFACE FLOW IN THE LARGE-SCALE SPURS-2 REGION OF STUDY. IN ADDITION TO THE ABOVE THE P.I. WILL MENTOR AND EDUCATE A NEW YOUNG SCIENTIST IN PHYSICAL OCEANOGRAPHY AND CLIMATE DYNAMICS. THIS WILL INVOLVE SHOWING HOW SATELLITE SSS AND OTHER SATELLITE OBSERVATIONS CAN BE LINKED WITH IN SITU OBSERVATIONS TO UNDERSTAND THE KEY PHYSICS OF THOSE OBSERVATIONS. SIGNIFICANCE OF THE PROPOSED WORK TO THE NASA SOLICITATION THE PROPOSED WORK MAKES EXTENSIVE USE OF AQUARIUS AND SMAP SSS AND LINKS THESE OBSERVATIONS TO OTHER SATELLITE AND IN SITU DATA TO UNDERSTAND THE INFLUENCE OF SSS ON INTERANNUAL FLOW IN THE EASTERN PACIFIC. THE PROJECT WILL PROVIDE A LARGE-SCALE INTERANNUAL CONTEXT FOR THE ONE-YEAR SPURS-2 EXPERIMENT.