Validation of Parametric Hurricane Models by ENVISAT ASAR

Abstract

In the past decade several satellite borne synthetic aperture radars (SAR) have been put into orbit. A synthetic aperture radar (SAR) not only records the intensity of the returned signal, but also the phase history of the backscattered radar signal and is processed to high spatial resolution images. To observe the structure of tropical cyclones at the sea surface RADARSAT 1 and ENVISAT ASAR Scan SAR images (400 x 400 km coverage) are the preferred datasets used. Together with optical imagery that yield information on the cloud tops they yield the possibility to investigate the three dimensional structure of tropical cyclones. The intensity images are calibrated and information on wind speed is derived. In addition sea surface features relating to cloud structure and rain rate are analysed. We give an assessment on the possibility to retrieve wind speed from SAR using the CMOD algorithms. In addition we have been investigating the following features in SAR images of hurricanes: - 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 in such high wind speed conditions.