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As a dominant source of tropical variability, the Madden-Julian oscillation (MJO) influences the ocean in many ways. One approach to observe the atmosphere-ocean relationship is by examining sea surface salinity (SSS) due to direct freshening by MJO precipitation. The convectively enhanced (suppressed) phase of the MJO is associated with negative (positive) SSS anomalies that propagate eastward along the equatorial Indian and Pacific oceans. In this study, primary MJO events are identified, and their SSS signatures are compared for the first time across multiple satellite salinity products (the European Space Agency's Soil Moisture Ocean Salinity; the National Aeronautics and Space Administration's Aquarius and Soil Moisture Active Passive) from 2010 to 2017. While all satellite missions are capable of detecting MJO signals and primary events on an unprecedented observational scale, we find that the use of the combined active passive algorithm increases signal robustness, with the strongest signal response in Soil Moisture Active Passive and Soil Moisture Ocean Salinity (+/- 0.2 psu) and the lowest in Aquarius (+/- 0.1 psu).

Plain Language Summary The Madden-Julian Oscillation (MJO) is the dominant form of intraseasonal variability in the tropics. It manifests as a pattern of eastward propagating enhanced and suppressed atmospheric convection over the equatorial Indian and Pacific Oceans. These atmospheric patterns can be easily observed in the surface ocean through sea surface salinity (SSS), as salinity is highly dependent on precipitation from convectively active events. Using satellite-derived salinity products, we can observe how the convection and precipitation associated with the MJO influence SSS. In this study, we compare the different salinity satellite products and their associated processing algorithms in order to determine which product most adequately captures the MJO signal in SSS. MJO events can be further described as being either primary or successive events, based on their duration, timing, and strength. After identifying these primary events during strong MJO years, we compared the SSS response to these events using the satellite salinity products. We found that the best salinity product was SMAP, which has higher spatiotemporal resolution and could reach closer to coastlines, particularly around the Maritime Continent. MJO studies of salinity are crucial, as salinity is the best way to see how precipitation events and air-sea interactions are translated into the ocean.