Investigations into CYGNSS-based soil moisture retrieval algorithms

NASA’s Cyclone Global Navigation Satellite System (CYGNSS) receives the forward scattered L-band GNSS signals between ±37^◦ latitudes. The received signals over land are previously shown to be highly sensitive to surface soil moisture (SM). Assuming coherent reflections over land, the CYGNSS bistatic radars can provide a spatial resolution of around 7 x 0.5 km and a revisit time of 1-2 days. SM retrieval at such a high spatio-temporal resolution could help advance hydro-meteorology and agriculture applications. This study examines case scenarios for determining the relations of CYGNSSdeliverables and available SM data as well as specifying the requirements for CYGNSS-derived SM retrieval. Preliminary results demonstrate moderate correlation between CYGNSS measurements and SMAP SM. However, the results also show that accurate derivation of high spatio-temporal SM products from CYGNSS measurements is a challenging problem due to the heterogeneous land covers, varying topography, and surface roughness.