| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 97 === As typhoon waves propagate out of the storm, it is called the swell. Since the group velocity of swell is swifter than the typhoon itself so that it often arrives shore earlier. Without warning the swell may cause serious property damage and even loss of human lives. Liang(1989) had proposed the typhoon swell forecast model. However, the swell hindcast for typhoon Ewiniar in 2006 is much higher than measured data. Therefore, in this study the author analyzes wave data at Hualain Harbor and typhoon data provided by Central Weather Bureau obtaining an empirical equation for typhoon swell period, i.e.
Tp=(0.041667×A+0.1321)×UR4s
A=(DD3×R4)/(TR4Br)^4
Where Tp is the peak period in second ,DD3 is the distance between typhoon center and the station in nautical mile, R4 is the radius of maxium winds in nautical mile estimated by Rodolfo''s method (2002), TR4Br、UR4s are the wave period at radius of maximum winds in second、sea-surface wind speed at radius of maxium winds in km.h-1 for stationary typhoon caculated by Bretschneider’s method (1976).
The swell height empirical equaiton is:
Hs=0.2331×(HR4Br)×[√(R4/DD3)]×λ
Where Hs is the significant wave in meter, HR4Br is the wave height at radius of maxium winds in feet for stationary typhoon calculated by Bretschneider’s method (1976).λ is the coefficient of wave height modification by Doppler effect(Liang,2003). Applying to typhoon Xangsane、Bilis、Korsa、Sinlaku,the typhoon swell hindcasting is acceptable.
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