ONE OF THE MOST INTRIGUING ASPECTS OF THE SEA SURFACE SALINITY (SSS) VARIABILITY IN THE INDIAN OCEAN IS THE PRESENCE OF WESTWARD PROPAGATING PERTURBATIONS ACROSS THE SOUTHERN BASIN AT SEASONAL TIME SCALES. THESE SIGNALS HAVE BEEN DESCRIBED IN SSS FIELDS RECENTLY DERIVED FROM AQUARIUS AND SMOS SATELLITES ARGO FLOATS AND HIGH-RESOLUTION MODEL SIMULATIONS. MOREOVER AQUARIUS HAS ALSO REVEALED THAT SSS PERTURBATIONS PROPAGATE EASTWARD NEAR THE JAVA-SUMATRA COAST IN THE SOUTHEASTERN BASIN. THE OVERALL GOAL OF THIS PROPOSAL IS TO UNDERSTAND THE SSS PROPAGATING SIGNALS THROUGH THE ANALYSIS OF SALINITY DATA FROM MULTIPLE SATELLITES. PROPAGATING SIGNALS ARE IMPORTANT TO UNDERSTAND BECAUSE THEY ARE THE BASIC MEANS BY WHICH TRANSFER OF INFORMATION ACROSS AN OCEAN BASIN IS ACCOMPLISHED AND A CRUCIAL PROCESS IN CLIMATE MODES SUCH AS THE INDIAN OCEAN DIPOLE. PROPAGATING SIGNALS IN VARIABLES SUCH AS SEA SURFACE HEIGHT (SSH) SEA SURFACE TEMPERATURE (SST) AND CHLOROPHYLL ARE KNOWN TO BE ASSOCIATED WITH PLANETARY WAVES AND EDDIES BUT IN THE CASE OF SSS THEIR DYNAMICS IS STILL LARGELY UNKNOWN. PREVIOUS STUDIES HYPOTHESIZE THAT THE WESTWARD SSS PROPAGATING ANOMALIES ARE SURFACE EXPRESSIONS OF ROSSBY WAVES OR EDDIES SINCE THEIR PHASE SPEEDS DECREASE WITH LATITUDE AND ARE OF THE ORDER OF LINEAR ROSSBY WAVE SPEEDS. MOREOVER THE EASTWARD PROPAGATION NEAR JAVA-SUMATRA DETECTED IN AQUARIUS FIELDS HAS BEEN SUGGESTED TO BE ASSOCIATED WITH COASTAL KELVIN WAVES. HOWEVER NO FURTHER STUDY HAS BEEN DONE TO CONFIRM THESE HYPOTHESES AND SEVERAL QUESTIONS ARE STILL OPEN. ARE THE SSS PROPAGATING FEATURES SURFACE EXPRESSIONS OF THREE-DIMENSIONAL PROCESSES? ARE THESE FEATURES RESTRICTED TO THE SOUTH INDIAN OCEAN? DO THEY OCCUR FOR EXAMPLE IN THE ARABIAN SEA A REGION WHERE PLANETARY WAVES AND EDDIES ARE KNOWN TO BE IMPORTANT FOR THE DYNAMICS? WHY ARE THEY DIFFERENT FROM THE PROPAGATING FEATURES IN SSH? ARE THEY COMPENSATED BY TEMPERATURE? THESE ARE SOME OF THE QUESTIONS THAT MOTIVATE THIS PROPOSAL. OUR PROJECT HAS TWO MAIN OBJECTIVES: (1) TO INVESTIGATE THE DYNAMICS OF SSS ANOMALIES IN RELATION TO PLANETARY WAVES AND EDDIES IN TWO REGIONS WHERE IT IS WELL KNOWN THAT THESE DYNAMICAL FEATURES ARE UBIQUITOUS: THE SOUTH INDIAN OCEAN AND THE ARABIAN SEA. THE AIM IS TO CONSTRUCT A BASIC UNDERSTANDING OF THE PHYSICAL MECHANISMS INVOLVED IN THE SSS PROPAGATING PERTURBATIONS IN THE EXTRAEQUATORIAL REGION. (2) TO EVALUATE THE RECENTLY RELEASED SMAP DATA IN THE INDIAN OCEAN SINCE THESE DATA CAN POTENTIALLY ALLOW A BETTER CHARACTERIZATION OF WAVE TYPES AND EDDY SIGNATURES IN SALINITY. PARTICULAR REGIONS OF INTEREST ARE THE NORTHWEST (ARABIAN SEA GULF OF ADEN AND RED SEA) AND THE SOUTHEAST (LEEUWIN CURRENT) INDIAN OCEAN. THIS PROJECT RESPONDS TO THE ROSES 2017 A.11 "OCEAN SALINITY SCIENCE TEAM" OBJECTIVES 1 AND 2 BY FOCUSING ON THE SSS VARIABILITY. A DETAILED EVALUATION OF THE SMAP AGAINST IN SITU OBSERVATIONS AND SMOS DATA WILL BE PERFORMED. THIS WILL PARTIALLY RESPOND TO OBJECTIVE 3 OF THE ROSES A.11. TO ACCOMPLISH THE OBJECTIVES LISTED ABOVE SSS MEASUREMENTS FROM AQUARIUS SMAP AND SMOS SATELLITES TOGETHER WITH ARGO SATELLITE SSH AND SST DATA WILL BE ANALYZED. ECCO OCEAN STATE ESTIMATE V. 4 (4.3) WHICH ASSIMILATES AQUARIUS DATA AND FORCING FIELDS WILL BE USED TO GAIN INSIGHT INTO THE PHYSICAL MECHANISMS INVOLVED IN THE SSS PROPAGATING ANOMALIES. THE PROPOSED RESEARCH WILL ADVANCE OUR UNDERSTANDING OF FUNDAMENTAL OCEANIC PROCESSES CONTROLLING THE SALINITY VARIABILITY IN THE INDIAN OCEAN. ALTHOUGH THE RESEARCH WILL BE RESTRICTED TO THE INDIAN OCEAN THE KNOWLEDGE OBTAINED WILL IMPROVE THE UNDERSTANDING ABOUT EXTRA-EQUATORIAL PROPAGATING SIGNALS IN SALINITY IN A BROAD SENSE INCLUDING THE ROLE OF MESOSCALE EDDIES. IT MAY ALSO PROMPT NEW QUESTIONS RELEVANT TO THE DYNAMICS OF OCEANIC PLANETARY WAVES WHOSE MAIN ADVANCES IN THE LAST TWENTY YEARS CAM FROM EXTENSIVE ANALYSES OF SSH SST AND OCEAN COLOR FIELDS BUT NOT YET FROM SSS.