台灣極端降雨氣候事件判定方法

Detection of the Climatic Extreme Rainfall Events in Taiwan

陳佳正(Chia-Jeng Chen) ； 盧孟明(Mong-Ming Lu)

《大氣科學》 35卷2期 (2007/06) Pp. 105-117

摘要

本文提出了一個以時雨量資料機率分佈為基礎的氣候極端降雨事件判別方法。根據台北、台中、台南、台東、花蓮五個測站1951-2005年的時雨量資料，先把原始資料以箱型計數(box-counting)方式組合為1hr、3hr、6hr、12hr、24hr、48hr 及72hr七種延時的降雨事件，然後根據線性動差方法(L-Moments)的推估結果採用皮爾森第三類(Pearson type Ⅲ)模擬降雨事件雨量的母體機率分佈，並據此計算超越機率為1%、5%、10%的雨量閾值，作為判斷氣候極端降雨事件的標準。
本研究的結果可用在建立氣候極端事件監測系統以分析每一個颱風帶來的豪大雨的氣候極端程度；不同延時事件的分析結果可以透露颱風雨受到大尺度環境背景場的影響程度。另外，本文提出的分析方法也可用於製作即時氣候監測作業的年度分析報告。以2005年為例，西部的三個測站的極端降雨事件發生頻率明顯高於氣候平均值；而東部的兩站並沒有頻率偏多現象，台東的事件甚至偏少。這些氣候現象的特徵值得即時記錄。
本文提出的機率法可克服百分位判定法必須每年更新閾值並且對資料長度相當敏感的缺點。在即時氣候監測分析方面，未來只需要每五年更新一次各測站極端降雨事件閾值標準即可。

關鍵字

極端降雨 ； 水文氣候 ； 氣候統計分析

並列摘要

This paper documents a procedure used for detecting the climatic extreme rainfall events. The hourly rainfall data during 1951-2005 at five Taiwan stations, namely, Taipei, Taichung, Tainan, Taitung and Hualien is analyzed. The hourly series are rearranged using the box-counting method into seven types of rainfall events, with the durations of 1, 3, 6, 12, 24, 48 and 72 hour, respectively. Pearson type Ⅲ distribution is chosen to simulate the rainfall events based on the L-Moments method. The threshold values corresponding to the exceedance probability of 1%, 5% and 10% are selected as the criteria for determining the climatic extreme rainfall events.
We demonstrate two areas that the analysis method described in this paper can be applied. One is to establish a typhoon rainfall analysis system for monitoring the extremity of rainfall events from the climate and statistical point of view. The shorter duration of an extreme event implies more intense rainfall and probably relatively less influence from large-scale flow patterns compared with local random processes. Another application area is to be used for documenting the annual frequency of extreme rainfall events in a real-time manner. The rainfall statistics provide background climate information for quantifying the extremity of the current climate. The background information is recommended to be updated in every five years.

並列關鍵字

Climate and Rainfall extremes ； Hydro-climatology ； Statistical Climatology