Dependence of SMOS/MIRAS Brightness Temperatures on Sea Surface Parameters
Yin, Xiaobin1; Boutin, Jacqueline1; Martin, Nicolas1; Spurgeon, Paul2; Ardhuin, Fabrice3; Reul, Nicolas3; Martin, Adrien1

SMOS (Soil Moisture and Ocean Salinity) has been successfully launched in November 2009 and its only payload, Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument, is the first interferometric radiometer at L band (1.4GHz) in orbit. MIRAS employs aperture synthesis in 2D with a Y-shaped antenna structure to create an image of emissions from the Earth surface at L-band over a range of incidence angles (0iã to 65iã) with a spatial resolution of 35 to 110 km. More than two years after launch the level 1C (L1C) brightness temperatures (TBs) reprocessed with the up-to-date ESA level 1 processing version (the Level 1 processor V5.04 and V5.05), have been released. It has been shown during the commissioning phase that the receivers onboard of MIRAS are affected by a short-term drift during each orbit, and a seasonal variation due to the thermal drifts of the antenna patch. Although a new antenna model is incorporated in the ESA L1 V5 processing to account for these variations, latitudinal and seasonal biases in L1C TBs are still observed. Using L1C TBs version 344, Yin et al. 2012 have proposed a new roughness/foam forward model. However, the derivation of that model was performed over a large latitudinal range and was possibly affected by latitudinal biases presenet in L1C v344, that have been partly corrected in L1c version 5. In this presentation, we reinvestigate the wind dependency derived from L1c v504 at multi-incidence angles and separately for various latitudinal bands and different seasons in order to separate artificial effects of TB drifts from sea surface effects. We also study the dependencies of TBs with wind direction (we did not find any significant correlation with previous SMOS L1c versions), mean square slope and significant wave height.


Yin, X., J. Boutin and P. Spurgeon, Optimization of L-band sea surface emissivity models deduced from SMOS data, IEEE Transactions on Geoscience and Remote Sensing, doi: 10.1109/TGRS.2012.2184547, 2012.