A LOOK AT CYGNSS DEPENDENCE ON SEA SURFACE SALINITY AND SEA SURFACE TEMPERATURE

The GNSS reflectometry response to sea surface salinity (SSS) and sea surface temperature (SST) is explored using CyGNSS normalized bistatic radar cross section measurements (NBRCS). SSS data from the NASA's Soil Moisture Active-Passive instrument is used for this analysis, including data from NOAA Optimum SST measurements. This study shows that CyGNSS NBRCS is in fact dependent on the SSS under all wind speed conditions, where CyGNSS NBRCS monotonically increases as the salinity increases. CyGNSS NBRCS dependence on the SST is shown to be weaker, compared to its dependence on the SSS. Impact to NOAA current 25 km wind speed product is also assessed where the wind speed error (i.e. CyGNSS-ECMWF) increases with decreasing salinity, whereas the error varies with increasing SST. These findings warrant the inclusion of both SSS and SST effects into future GNSS based wind retrieval algorithms.