Strategies for validating and directions for employing SMOS data, in the Cal-Val project SWEX (3275) for wetlands

Abstract. The paper tries interpreting how the method of SMOS observations realizes managing the problem of large scales and the target heterogeneity by means of employing the polarization angular signature. Land surface target on the Earth is naturally heterogeneous in its continuity of physical and biophysical properties. Soil moisture (SM) retrieval from SMOS data requires using the model CMEM to determine relations between the temperature brightness and water related properties and conditions, which are anchored to the ground by auxiliary data. SM retrieval must start from the conditions at least approaching physical reality. SMOS performs the data fusion in NRT (Nearly Real Time) in a very specific way, what is a new quality added to EO (Earth Observations). The paper demonstrates several effects of employing the SM retrievals from L1C data. Authors explain how they validate few selected test sites in Poland, and come to conclusions on choosing a strategy focused on validating single sites. Finally, they come to an understanding that SM retrieval is an advanced statistical method requiring good referencing to ground based physical conditions in large scales, worth confronting the shallow water content obtained from SMOS to that assessments of the total water content on continental scales, which available from effects of gravitational missions.