The Global SMOS Level 3 daily soil moisture and brightness temperature maps

Abstract

Abstract. The objective of this paper is to present the multi-orbit (MO) surface Soil Moisture (SM) and angle binned Brightness Temperature (TB) products for the SMOS (Soil Moisture and Ocean Salinity) mission based on the a new multi-orbit algorithm. The Level 3 algorithm at CATDS (Centre de Traitement Aval des Données SMOS) makes use of multi-orbit (multi-revisits) retrieval to enhance the robustness and quality of SM retrievals. The motivation of the approach is to make use of the temporal auto-correlation of the vegetation optical depth (VOD) to enhance the retrievals when an acquisition occurs at the border of the swath. The retrieval algorithm is implemented in a unique operational processor delivering multiple parameters (e.g. SM and VOD) using angular signatures, dual polarization and multiple revisits. A subsidiary angle binned TB product is provided. In this study the L3 TB V300 product is showcased and compared to SMAP (Soil Moisture Active Passive) TB. The L3 SM V300 product is compared to the single-orbit (SO) retrievals from Level 2 SM processor from ESA (European Space Agency) with aligned configuration. The advantages and drawbacks of the Level 3 SM product (L3SM) product are discussed. The comparison is done at global scale between the two datasets and at local scale with respect to in situ data from AMMA-CATCH and USDA-ARS WATERSHEDS networks. The results obtained from the global analysis show that the MO implementation enhances the number of retrievals up to 9 % over certain areas. The comparison with the in situ data shows that the increase of the number of retrievals does not come with a decrease of quality. But rather at the expense of an increased lag of product availability from 6 hours to 3.5 days which can be a limiting factor for forecast applications like flood forecast but reasonable for drought monitoring and climate change studies. The SMOS L3 soil moisture and L3 brightness temperature products are delivered using an open licence and free of charge by CATDS (http://www.catds.fr).