Spaceborne Demonstration of GNSS-R Scattering Cross Section Sensitivity to Wind Direction

Abstract

This letter investigates the sensitivity of the ocean surface bistatic scattering cross section measured by the Cyclone Global Navigation Satellite System (CYGNSS) to wind direction using the kurtosis of the delay-Doppler map (DDM) samples within a given area. The azimuthal dependence of the kurtosis is modeled by a cosine expansion of the relative wind direction, as is done in scatterometry for the radar cross section. The harmonic coefficients of the model depend on wind speed and incidence angle. Results show a coefficient of determination ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R^{2}$ </tex-math></inline-formula> ) between 0.6 and 0.9 for wind speeds between 4 and 10 m/s and negligible sensitivity outside this range. This study opens the door to the potential of using CYGNSS data for wind direction estimation.