Observation of Hurricane Winds Using Synthetic Aperture Radar

In the last five years several synthetic aperture radar (SAR) images of hurricanes have been acquired by the Canadian satellite RADARSAT-1 as well as the European satellite ENVISAT. Several of these SAR images have captured hurricanes of category 4 and 5. These SAR data give the unique opportunity to investigate the possibilities of SAR data for observation and forecast of hurricanes. In this study wind fields under hurricane conditions are retrieved from the SAR utilizing WiSAR. WiSAR is an algorithm, which has shown to give good results under low and moderate wind conditions. The algorithm extracts wind directions from wind induced streaks imaged by the SAR at scales above 200m. Wind speeds are extracted from the SAR measured normalized radar cross section (NRCS) utilizing the C-band model CMOD5, which describes the dependency of the NRCS on wind. It will be shown that the algorithm enables to measure wind directions as well as wind speeds of over 50 ms−1. The SARretrieved wind fields are compared to results of a high resolution numerical hurricane model.