SMOS the water cycle mission : an overview, Earth Observation for water cycle science
Résumé
The SMOS (Soil Moisture and Ocean Salinity) satellite was successfully launched in November 2009. This ESA led mission for Earth Observation is dedicated to provide soil moisture over continental surface (with an accuracy goal of 0.04 m3/m3) vegetation water content over land and ocean salinity. These geophysical features are important as they control the energy balance between the surface and the atmosphere. Their knowledge at a global scale is of interest for climatic and weather researches in particular in improving models forecasts. The SMOS instrument measures the passive microwave emission of the Earth surface at a frequency of 1,4 GHz (L‐band). The instrument is an interferometer and provides brightness temperatures with an average resolution of 40 km, at several angles and dual polarizations. Data are acquired at two times in a day at 6 am and 18 pm (local time) and insure a complete coverage of the Earth surface in 3 days with a sampling of 15 km. The main products of the mission are of course Soil Moisture and Sea Surface salinity, but also vegetation opacity (directly related to water content) of vegetation covers including forests, surface dielectric constant for level two but also brightness temperatures at the surface, strong winds, root zone soil moisture and RFI (radio frequency interferences) maps. From Level 2 SMOS data several groups have started making new products several of them being either operational or on the verge of being such. We will show some of them or refer to related presentations. They include freeze defreeze (FMI), thin sea ice (Klimat Center Hamburg), near real time brightness temperatures and soon soil moisture (ECMWF), root zone soil moisture and drought indices (USDA and CESBIO). We are also working on more elaborate products such as water fractions, flood risk indexes, improved precipitation with use of assimilated SMOS data, etc. The focus in this presentation will be given to the latter new science products. The purpose of this communication is to present the mission results after almost 6 years in orbit and a major re‐processing as well as some outstanding results already obtained. A special attention will be devoted to level 2 products and to the retrieval quality improvements from version 3 (at launch) to the current version 620.