Aquarius/SAC-D Ocean Salinity Mission Science Overview

Scheduled for launch in 2009, the international Aquarius/SAC-D satellite will begin a mission to map the global sea surface salinity (SSS) field and its variability from space. The overarching scientific goal is to provide the essential data to study the interactions between the ocean circulation, global water cycle and climate. Key scientific issues to address are (1) mapping large expanses of the unexplored ocean, (2) understanding the seasonal and interannual SSS variations and the link to precipitation, evaporation and sea-ice patterns, (3) links between SSS and circulation variations in the North Atlantic overturning circulation, (4) air-sea coupling processes in the tropics that influence El Nintildeo, and (4) closing the marine freshwater budget. The satellite will provide repeat global coverage every 7 days with a footprint resolution ranging from 90 to 150 km over a three-beam ~390 km wide swath. Monthly SSS means will have an average root mean square (rms) accuracy of 0.2 psu at a spatial resolution of 150 km. Accuracies will be somewhat better in the tropics than high latitudes. Coincident microwave measurements of rain, sea ice and surface wind speed will be made with a resolution of about 45 km. The mission duration is initially three years, with probable extensions of two or more years.