IMPROVED CALIBRATION OF CYGNSS MEASUREMENTS FOR DOWNBURSTS IN THE INTERTROPICAL CONVERGENCE ZONE

CYGNSS is a space borne GNSS-R mission that uses the GPS L1 signal which usually has negligible attenuation due to rain. However, under heavy precipitation its effects need to be properly accounted for. In this paper, we characterize the effects of precipitation on the CYGNSS Normalized Bistatic Radar Cross Section (NBRCS) resulting from propagation losses, from rain induced surface roughening, and from increased near-surface wind associated with the presence of rain. Proper accounting for these effects is necessary to accurately retrieve ocean surface wind speed under heavy precipitation and, for example, to resolve the horizontal wind shear present in the rain bands of the ITCZ.