臺灣東部梅雨鋒面降水中尺度氣候法之預報校驗

Forecast Evaluation for the Meiyu Frontal Rainfall over Eastern Taiwan Using Mesoscale Climatology

陳泰然(George Tai-Jen Chen) ； 王子軒(Tzy-Shyuan Wang) ； 周鴻祺(Hon-Chi Chou) ； 黃心怡(Shin-Yi Huang)

《大氣科學》 42卷1期 (2014/06) Pp. 1-27

摘要

本文利用中央氣象局1997~2006年5~6月每3小時之地面天氣圖，分析臺灣與鄰近地區的鋒面位置，結果顯示有54、50及46道鋒面分別通過Post-TAMEX臺灣東部分區13（宜蘭縣）、14(花蓮縣）及15（臺東縣）。以各分區之地理位置中心點為準，將鋒面通過該點時間定為t_0（即t = 0），分析鋒面過境前後之降雨氣候特徵，包括降雨機率、降雨強度及豪（大）雨發生機率，並以2007年與2008年梅雨季鋒面過境前後之觀測資料進行校驗，以了解中尺度氣候值法（CL法）在臺灣東部地區於鋒面過境前12小時至後24小時內之定量降水預報能力，以及在各分區之預報可應用性。結果顯示，各分區之降雨機率與降雨強度在鋒面過境後皆較過境前為高，且有由北往南遞減趨勢，顯見梅雨鋒之舉升作用在東部地區降雨扮演重要角色。中尺度氣候法預報校驗顯示，在鋒面過境期間（前12小時至後24小時），CL法之降雨機率在3~6小時預報缺口具有預報參考價值，對豪雨而言亦然，但對降雨強度幾無預報能力。整體而言，臺灣東部地區CL法具有3~6小時預報能力，特別是在3小時之後，持續法誤差普遍增加之時，氣候值法可提供預報參考價值，以彌補數值預報模式之預報缺口。

關鍵字

氣候變遷 ； 東亞季風 ； 政府間氣候變遷小組第四期評估報告

並列摘要

Surface weather maps at 3-hour intervals in the period of May-June 1997~2006 from Central Weather Bureau were used to analyze the position of the fronts over Taiwan and its vicinity. The results showed that there were 54, 50, and 46 fronts, respectively, passing Post-TAMEX subdivision 13 (Yilan County), 14 (Hualien County), and 15 (Taitung County).The time at which a front passed the geographically central point of each subdivision was set as t_0 (t = 0), and the climatological characteristics of rainfall, including probability of precipitation (PoP), intensity of precipitation, and the probability of the occurrence of heavy rainfall, were analyzed. Furthermore, the mesoscale climatological method (CL method) was used to evaluate the ability of the quantitative precipitation forecast using observational data of 2007~2008 Meiyu season. The results showed that both the PoP and intensity of precipitation in each subdivision for after the passage of the front were higher than that for before and had the tendency of the southerner, the smaller. Thus it is obvious that the lifting effect of the Meiyu front played an important role in the precipitation in eastern Taiwan. The verification of forecasting using the CL method showed that during the passage of the Meiyu front (from 12 hours before the passage to 24 hours after the passage), the probability of precipitation of CL method offered valuable reference for forecasting at the forecasting gap 3-6 hours, and the same to heavy rainfall although precipitation intensity of CL method only with little skill. As a whole, CL method was capable of 3-6 hours forecast in eastern Taiwan, and could offer valuable reference for forecasting to compensate the forecasting gap of the numerical forecasting model, especially when the error of the persistence forecast generally increased after 3 hours.

並列關鍵字

Mei-Yu season ； Probability of precipitation (PoP) ； Mesoscale climatological method (CL method)