Presented at the 2016 Ocean Sciences MeetingAt the Eastern Tropical Pacific between the Panama Bight and the Galapagos Island a large region of low sea surface salinity (SSS) extends from the coast to around 90°W. It exhibits a strong seasonal cycle and distinct spatial pattern. The atmospheric and oceanic variability over this region is mainly modulated by the migration of the Intertropical Convergence Zone and El Niño Southern Oscillation. In addition, some of the most intense deep convective storms in the world take place over it making the Colombian coast the rainiest places on Earth, with average annual precipitation exceeding 12,500 mm. The mechanisms controlling the spatial and temporal variability of the SSS at this region are far from being fully understood. Is the SSS controlled by Ekman advection or freshwater exchanges, or something else?. So, this work aims to present a characterization of the interannual variability of SSS in the region delimited by 4°S-10°N and 100°W-75°W through satellite observations and numerical modeling. We use the SSS products derived from NASA-CONAE Aquarius (with a spatial resolution of 1°x1°) and Soil Moisture and Ocean salinity (SMOS, spatial resolution ¼° and 1°) missions for the period between 2009 and 2014 and an ensemble of numerical integration using the regional ocean model ROMS-Agrif under different atmospheric and oceanic forcing scenarios.