An algorithm to retrieve sea surface salinity from SMOS L-band radiometric measurements

Abstract

The European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission, the second of the ESA's Living Planet Program Earth Explorer Opportunity Missions, aims at obtaining global maps of soil moisture and sea surface salinity from space for large scale and climatic studies. This mission, with launch scheduled for early 2008, uses and L-band (1400-1427 MHz protected to human emissions) Microwave Interferometric Radiometer by Aperture Synthesis (MIRAS) to measure brightness temperature at the Earth surface at horizontal Th and vertical Tv polarizations (a fully polarized mode is also implemented and will be tested during the commissioning phase). These radiometric parameters will be be used together to retrieve the two geophysical variables, following specifically designed algorithms that will be applied when the satellite field-of-view is covering land or ocean surfaces. The retrieval of salinity is a complex process that requires the knowledge of the other evironmental information and an accurate processing of the radiometer measurements, due to the narrow range of ocean brightness temperatures and the strong impact in the measured values of different gephysical parameters (as sea state) other than salinity. Here we present the baseline approach chosen by ESA to retrieve sea surface salinity from MIRAS data, as it has been developed and implemented by the joint team of scientists and engineers responsible for the SMOS Ocean Salinity Level 2 Prototype Processor