Retrieval of sea surface velocity during tropical cyclones from RAD ARS AT-1 ScanSAR Doppler centroid measurements

This paper presents here aims at the retrieval of sea surface velocity during tropical clones using RADARSAT-1 ScanSAR Doppler centroid measurements. The sea surface velocity can be estimated by comparing Doppler shift anomalies between predicted and estimated Doppler centroids. The predicted Doppler centroid, defined as the Doppler centroid assuming that the target is not moving, is calculated based on the geometry model. While the estimated Doppler centroid, representing the moving target, can be extracted directly from SAR raw signal data by applying the Average Cross Correlation Coefficient (ACCC) method. In this study, we present characteristics of the sea surface response to tropical cyclones such as the size of hurricane eye or intensity and the spatial patterns of surface velocity from the center of hurricane. And we present the first attempt to derive sea surface velocity using RADARSAT-1 ScanSAR Doppler centroid measurements during two different hurricane (Typhoon Xangsane and Hurricane Lili) and three sequential cases of Hurricane Lili, especially when using inaccurate satellite´s orbit and attitude information with wide coverage, such as RADARSAT-1 ScanSAR wide mode. Although the result was compared with one drifting buoy data in a single location during Typhoon Xangsane, it clearly shows that the sea surface velocity during tropical cyclones can represent the sea surface current.