Ocean surface salinity - the why, what and whether, in Consultative meeting on Soil Moisture and Ocean Salinity measurement requirements and radiometer techniques (SMOS

In this paper a range of oceanographic problems are reviewed, for which knowledge of the ocean surface salinity is an important factor (which will answer the question why the measurements are needed). These problems include: the circulation of the ocean on global scales, the effect of changes in salinity on the tropical ocean, the formation of deep water in the high latitude oceans, the changes in salinity at the meso-scale (that is, those related to fronts and eddies) and the changes in salinity in coastal waters. The possibility of using surface salinity to constrain estimates of the exchange of fresh water at the sea surface E-P (evaporation minus precipitation) will also be considered. On the basis of the review, requirements for the spatial and temporal sampling, and the accuracy of the measurements necessary to address the various problems will be derived (which will answer the question what measurements are needed). These will then be compared to what is known of the capabilities of proposed ocean surface salinity sensors (such as MIRAS and ESTAR). From this comparison, conclusions will be drawn about the usefulness of the data that is likely to be acquired from the sensors, and what improvements in capability might be necessary to increase the utility of such measurements (which will answer the question whether the measurements are useful). In addition, various issues are raised that need to be considered in more detail if measuring salinity from space is to be more than just a theoretical possibility. 1