Investigation of Typhoons using ERS-2 SAR Wave Mode Data

Abstract

It is well known that typhoons are hard to forecast because of their complicated dynamical behaviour. In this study a new global data set of reprocessed ERS-2 wave mode data is used to study typhoons assessing the potential of these data for improving typhoon forecast. Operating in Wave mode the ERS SAR acquires high resolution images of 10 by 5 km size every 200 km along the track yielding a patchy coverage of the global oceans with about 1500 scenes taken each day. The images contain information on both ocean waves and near surface wind. The typhoon TRINING in November 1999 is analyzed. Local wind speeds are estimated from the SAR image intensity. Results are compared with collocated ERS-2 altimeter measurements of wave height and wind speed as well QuikScat wind vectors. The potential of the high resolution SAR information with regard to the analysis of rain cells and atmospheric turbulence is dicussed. SST measurements obtained from spaceborne radiometers are used as complementary information. The combined use of altimeter wind speeds and radar cross sections obtained from SAR to estimate wind vectors is investigated.