Tropical Cyclone Parameters Derived from Synthetic Aperture Radar (SAR) Images

Abstract

Ocean waves play an important role in the dynamics of extreme events like hurricanes or typhoons by conditioning the air/sea fluxes of momentum, heat and moisture. In this study a data set of ENVISAT ASAR Scan SAR images (400 times 400 km coverage) are used to observe the structure of tropical cyclones and typhoons at the sea surface. The following features of hurricanes were determined: wavelength and direction of boundary layer rolls for information of mixed boundary layer depth, radius of maximum wind speed, sea state in terms of wavelength, and direction. These image parameters are related to parametric models of hurricanes and validated by aircraft measurements from the National Hurricane Center (NHC). The work aims at the improvement of prediction of the cyclone track, intensity and sea state at these high wind speed conditions. The paper focuses on two illustrative case studies from August 2005, e.g., images of Hurricane Katrina acquired over the Gulf of Mexico and of Typhoon Talim acquired over the NW Pacific.