旋轉與強度變化效應於估算熱帶氣旋登陸後之降雨潛勢

鄭丞衡(Cheng-Heng Cheng)

指導教授 ： 劉振榮

國立中央大學/太空及遙測研究中心/遙測科技碩士學位學程/碩士(2012年)

摘要

颱風所帶來的豪大雨往往對我們生命以及經濟造成極大傷害，因此準確的颱風降水預測對於防洪減災任務相當重要。Kidder et al. (2005)提出熱帶氣旋降雨潛勢(Tropical Rainfall Potential Technique, TRaP)的估算方法，可用來快速的估算颱風累積降水分佈。由於其TRaP方法並未考慮颱風旋轉效應以及降雨率隨時間變化關係，因此以TRaP方法估算降雨時往往造成可觀誤差。本研究引用Kaplan et al. (1995)方法，建立估算大陸華南沿海地區熱帶氣旋登陸後強度遞減模式，並嘗試利用氣旋登陸時初始強度、季節、及強度加季節等三種分類，分別建立強度變化估算模式，結果顯示，以強度分類建立的估算模式所估算的強度變化結果最佳。

降雨估算方面，本研究使用TRaP方法，搭配本研究所建立的氣旋強度遞減估算模式來預測氣旋登陸後降雨率變化，以及使用Liu et al. (2008)所提出颱風旋轉角度估算方法，以估算氣旋登陸後累積降雨潛勢。因受到測站資料時間解析度限制，本研究只分析6、24小時累積降雨。估算得之的6小時累積降雨結果顯示僅考慮平移時其估算結果與測站相關係數為0.74，而同時考慮旋轉加強度變化的相關係數則提升為0.78；而24小時累積雨量估算結果顯示僅考慮平移時其相關係數為0.51，但加入了旋轉以及強度變化因素後其相關係數提升至0.60，且RMSE也從37.1 mm/24hr大幅降低至13.8 mm/24hr。整體而言，其結果顯示當考慮旋轉及強度變化因素後可有效提升估算降雨的準確度。

關鍵字

熱帶氣旋降雨潛勢 ； 強度遞減模式

並列摘要

Typhoons usually pose a serious threat to the livelihood of people. Therefore, making accurate rainfall predictions has been a key focus in weather forecasting. Kidder et al. (2005) introduced a method called the Tropical Rainfall Potential Technique (TRaP) to predict the accumulated rainfall. However, the method didn’t consider the cyclone intensity variations and rotation, which may cause significant errors when estimating the rainfall potential. The intensity decay model (Kaplan et al., 1995) is used in this study to estimate the landing cyclone intensity variations. The different landing typhoon intensity, seasons, and intensity plus seasons, were categorized and tested in this model, the results show that the consideration of intensity had the best result.

Based on the TRaP method, the study considered the cyclone rotations (Liu et al., 2008) and intensity variations in estimating the rainfall potential in the southern China coastal area. Due to the limitation of the rain gauge temporal resolution, only 6 and 24 hours accumulated rainfall were analyzed in this study. For the 6 hrs rainfall potential, results revealed that the correlation was 0.74 when only the shift-motion was considered. Yet, the correlation rose to 0.78 when the tropical cyclones’ intensity and rotation changes were also taken into account. In terms of the 24 hrs rainfall potential prediction, the correlation increased from 0.51 to 0.60 and the RMSE decreased from 37.1 to 13.8 mm/24hr when intensity variations and rotation change were factored in. In general, the results showed that the additional considerations in this study could notably improve the TRaP method accuracy.

並列關鍵字

tropical rainfall potential ； intensity decay model

參考文獻

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