Metop ASCAT Soil Moisture Time Series

The soil moisture product represents the water content in the upper soil layer (< 2 cm) in relative units between totally dry conditions (0%) and total water capacity (100%). The time series are available on a discrete global grid (DGG) with a spatial resolution of 25 km (grid spacing 12.5 km). The temporal sampling rate is irregular (every 1-2 days) and depends on the latitude. Each surface soil moisture estimate has an associated noise value, indicating the uncertainty. The soil moisture product has not been pre-filtered, meaning that a masking of invalid measurements (e.g. frozen ground, snow cover) by the user is highly recommended before further processing.


The surface soil moisture data are retrieved from the radar backscattering coefficients measured by the ASCAT (Advanced scatterometer) instrument on board the MetOp-A satellite using a change detection method, developed at the Research Group Remote Sensing, Department of Geodesy and Geoinformation (GEO), Vienna University of Technology (TU Wien). In the TU Wien model, long-term scatterometer data are used to model the incidence angle dependency of the radar backscattering signal. Knowing the incidence angle dependency, the backscattering coefficients are normalised to a reference incidence angle (40°). Finally, the relative soil moisture data ranging between 0% and 100% are derived by scaling the normalised backscattering coefficients between the lowest/highest backscatter values corresponding to the driest/wettest soil conditions.


Category Soil Moisture
Variable SSM
Unit Degree of saturation (%)
Product Level 2
Resource Type series
Data Structure vector
Spatial Resolution 25km
Spatial Sampling 12.5km
Satellite/Sensor MetOp-A/ASCAT
Originator TU Wien
Owner H-SAF
Distributor H-SAF
Processor TU Wien
Principal Investigator TU Wien
Reference System WGS84