New BEC SMOS products: improvements and performances from Level 1 to Level 4

Abstract

More than six years have been spent since the launch, on November 2, 2009, of the European Space Agency¿s (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite carrying a microwave synthetic aperture radiometer working at 1.4 GHz. The aim of the mission is to provide Sea Surface Salinity and Soil Moisture observations, with a spatial resolution of 30-50 km, and an accuracy suited for climate studies. Starting from L1brightness temperature (TB) observations, experimental Sea Surface Salinity (SSS) and Soil Moisture (SM) maps are being developed and progressively distributed at the Barcelona Expert Center (BEC). Data are distributed in NetCDF format using THREDDS and maps are served through a Web Map Service (ncWMS), both at the BEC distribution data website (http://cp34-bec.cmima.csic.es/). BEC ocean products are experiencing a great evolution thanks to the introduction of new key algorithms at different levels of the processing chain. At level 1, nominal TBs are replaced by the nodal sampled ones. Nodal sampling is a new image reconstruction technique that reduces tsidelobes and ripples that associated to abrupt changes in TB (see [1,2]). At level 2, systematic biases are removed by referring them to SMOS-derived climatologies. As a result, the new maps present a sharp reduction of the land-sea contamination. At level 3, the correlations of the optimal interpolation algorithm have been improved such that the resulting maps show a more coherent spatial structure at all the scales. Finally, at level 4, the spatial and temporal resolutions have been increased by means of multifractal synergy techniques, which allow generating global daily SMOS SSS maps (see [3,4]). Besides, all these improvements allow the production of a new SSS product fitted to polar regions. Surface density products are now also available in our website. For land applications, high resolution maps (1km at Iberian Peninsula) are produced using reliable non-remote sensing auxiliary parameters so that now these products are weather-independent and with full spatial coverage. That allows the generation of a new product focused on the fire forest risk prediction. Finally, new cryospheric sea ice concentration products have been developed following the methodology described in [5]. In summary, the new generation of BEC products, to be distributed soon, represent a real leap forward in quality that will enable a new generation of geophysical studies