SSM/I衛星資料在颱風降雨潛勢預報上之應用

Apply SSM/I data to predict Typhoon Rainfall Potential

趙俊傑(Chun-Chieh Chao)

指導教授 ： 劉振榮

國立中央大學/地球科學學院/大氣物理研究所/博士(2011年)

摘要

對於侵臺前之颱風降水預報，氣象雷達之掃描區域有限制性，而模式亦有初始化及參數化之相關問題，皆無法很準確地預測短期的強烈降水，而被動式微波輻射計推估降水預報是可行的方法。Kidder et al(2005)使用SSM/I、TMI及AMSU等被動微波輻射計估算，參考美國官方之颱風最佳路徑，預測豪大雨之24小時潛勢預報，此技術(Tropical Rainfall Potential，簡稱TRaP)提供一個快速又實用的方法，應用此技術預測降雨量比中尺度數值預測模式更接近於實際觀測(Ferraro et al，2005)。
本研究參考TRaP方法，加上颱風螺旋雨帶的變化，以台灣附近外島雨量站當作驗證，結果可以增進TRaP的降雨準確率將近百分之四十，另外利用中國大陸東南沿海地區測站驗證，結果可以增進TRaP的降雨準確率將近百分之十二，若考慮強度變化加入TRaP中，則有微幅的改善，另外本文利用紅外線雲圖計算颱風雲圖旋轉速度，並以此推估颱風強度的方法，則得到不錯之結果。
另外，本研究亦探討地形效應對TRaP潛勢降雨預測之影響，結果顯示迎風面對於TRaP有低估的情況，背風面則有高估的情形，故本研究參考Lin等(2001)的方法，改善颱風降雨潛勢的計算，有地形修正之ETS技術得分比無地形修正要佳，尤其在颱風雨帶旋轉角度0至4度修正幅度較大，技術得分增加幅度將近百分之十。
最後評估中央山脈地形對侵台颱風風雨分佈之鎖定效應，可以增進颱風潛勢降雨預測之結果，對未來台灣地區颱風潛勢降雨方法的改良有助益。

關鍵字

衛星遙測 ； 潛勢降雨 ； 颱風

並列摘要

Pursuing accuracy of quantitative precipitation forecast is a scientific goal and also people’s expectation, especially for disastrous rainfall predictios of landing typhoons. All typhoons get birth and develop on ocean where traditional observations are scarce for them. Therefore, weather satellite observations are very crucial. The typhoons are coming and approaching to offshore area, where are only a few observations around. The scanning from land-based weather radar for rainfall structures of typhoons are valuable, but only could be available while typhoons in near coast. Satellite-borne microwave radiometers can be used to measure instantaneous rain rates through the full cover of typhoons which are very suitable for typhoon rainfall potential prediction.
As for simple Tropical Rainfall Potential (TRaP, Ferraro et al., 2005), it is assumed that estimated rain rates are correct and no intensity change and rain structure change occurred during typhoon’s movements. First we use JTWC’s typhoon best track data to predict rainfall potential of next six hours. The results are validated by offshore rain gauges data. The second, the rainband rotation rates are computed and further are applied to predict rainfall potential which be validated in Tainwan offshore island and mainland china. It could be reached about 40% improvements. The third, intensity changes are taken into considerations in the TRaP. It could have little improvement after comparing to the simple TRaP. Finally terrain effects are calculated during the TRaP processes and are discussed when estimating the typhoon rainfall potential. The performances of the results have further improvements.

並列關鍵字

rainfall potential ； satellite remote sensing ； Typhoon

參考文獻

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