First Surface Soil Drying Validation in A Productive Area in Central Argentina

Surface soil moisture (SSM) dry-downs have been employed to compare independent data sources on the dynamics of water in soils, including such remote sensing, land surface models and in-situ measurements, which are often difficult to contrast with standard methodologies. The soil drying approach summarizes the soil response to climate as well as surface conditions during a dry period. In this work it is estimated as the SSM e-folding decay, named as dry-down time scale. This is the first assessment over eastern Cordoba, Argentina, a region with a very high cultivated land fraction that was subject of important agricultural changes in the last decades. SMOS SSM product (derived from microwave measurements at L band) is validated with in-situ SSM measurements provided by the National Commission for Space Activities during 2012-2018. Both products agree in showing that the austral spring season has the largest number of dry-down events for the whole period. The dry-down time scale sensitivity to the chosen detection method as well as the data sampling frequency is larger in summer than in spring. A faster soil drying in SMOS than in In-situ SSM is found, likely as a consequence of the shallower sensing depth of the first. This dependency seems to be more important than the temporal sampling frequency in the SSM data.