Abstract
Tokuda and Nagamatsu (1999) proposed an automatic extraction method of surface current information from high-frequency radar echoes. Accuracy of this method was proved to be stable without the aid of an expert. We used the method, called "regression line method", to analyze Doppler spectra contaminated with high levels of external noise, and found it was unable to extract the surface current. Because power of the noise exceeded that of the so-called "first-order" echo which contains informations of the surface current.
From this reason, we have developed a new algorithm on the basis of the Bragg resonant mechanism that can extract the first-order echo from the spectra contaminated above. The algolism was verified by the following facts.
Surface currents extracted by this algorithm were in good agreement with those measured by a current meter, which were measured at the same point simultaneously. The eddy pattern appeared on the surface current map showed the remarkable similarity to the one appeared on the image data of MESSER of MOS-I, though each observation was carried out at different times.
Consequently we can conclude that the regression line method used in combination with this algorithm can be a more reliable method for automatically extracting surface currents.
