Downscaling Earth Observation Operational Soil Moisture Products Using multi-sensor Satellite Data: “A Triangle Inversion Approach"

Monitoring key parameters that drive land-surface processes, such as surface soil moisture (SSM)), is essential for understanding global biogeochemical cycles, including those of water, energy, and carbon. While Earth Observation (EO)-based SSM products have demonstrated significant potential, their practical application is often limited by coarse spatio-temporal resolution. Therefore, downscaling these operational products is a critical scientific challenge for enabling their effective use in regional and local-scale applications.

This study’s aims at presenting an innovative approach for downscaling operational soil moisture products using a variant of the so-called “triangle” method, named the “simplified” triangle. The use of the proposed technique is demonstrated herein using the European Space Agency's (ESA) operational soil moisture product from the Soil Moisture and Ocean Salinity (SMOS) and optical data from ESA’s Sentinel-3 platform. The enhanced spatial SSM estimates are compared against near collocated reference ground data from multiple validated experimental sites across Europe. The results obtained indicate a satisfactory agreement, confirming the proposed approach's promising potential to accurately estimate key land-surface interaction parameters. Conceptually the proposed herein methodological framework is applicable to any operational product, a topic of further investigation.