ASCAT and SMOS soil moisture retrievals: A comparison over Europe and Northern Africa

An analysis of two remotely sensed soil moisture data sets, derived from the Advanced SCATterometer (ASCAT) and from the Soil Moisture ad Ocean Salinity (SMOS) radiometer, has been performed. This analysis has been carried out within the framework of an activity aiming at validating the EUMETSAT Hydrology Satellite Application Facility (H-SAF) soil moisture products derived from ASCAT over Europe and North Africa. The data acquired from 2010 to 2012 have been used. We have also considered the soil moisture maps predicted by a Land Surface Model, namely the ERA Interim/Land data set. Results demonstrate that, after a conversion of the H-SAF saturation index into a volumetric soil moisture, SMOS and ASCAT present a fairly good degree of correlation and their consistency depends on season, geographical zone and surface land cover. Moreover, to estimate the relative amount of error affecting the different sources of soil moisture maps, the Triple Collocation technique has been implemented. Such an approach has been applied also considering different conditions in terms of season, time of the day and data filtering approaches.