台灣地區春梅雨期短期氣候之模擬研究

Short Term Climate Simulation on Springtime and Mei-Yu Period of Taiwan

蕭志惠(Chih-Hui Shiao) ； 莊漢明(Hann-Ming Henry Juang)

《大氣科學》 30卷4期 (2002/12) Pp. 291-312

摘要

本報告為台灣地區春梅雨時期（3至6月）之短期氣候模擬研究。目的在探討美國國家環境預報中心(NCEP)區域波譜模式(RSM)對該時期降水變化之模擬能力，及分析東亞和台灣地區偏濕降水時的平均距平環流特徵。
實驗期間為1995年至2001年，並以中央氣象局全球預報系統之分析場作為區域模式之初始值及背景場。區域模式之模擬降水將分別計算東亞(110°E-130°E和12°N-35°N)及台灣地區(120°E-122°E及22°N-26°N)之平均降水距平百分比，並以正負0.5個標準差區分為偏乾、正常及偏濕三種類型，分別與東亞地區之GPCP降水分析資料及中央氣象局地面25個測站之雨量作校驗。中央氣象局全球模式的分析場則同時作為模式距平環流的校驗之用。
模擬結果顯示：在東亞地區降水為偏濕或台灣地區降水為偏濕時，東亞地區之中低層大氣都出現逆時針方向的距平環流。在850hPa，前者以南海為中心、後者以東海為中心，影響範圍均涵蓋整個東亞地區。受環流中之乾冷東北氣流所影響，當東亞地區降水普遍偏濕時仍有乾區出現在華南地區；在台灣地區降水為偏濕時，則中緯度及熱帶普遍偏乾。環流南支之西風及南風距平與強烈降水的位置有非常密切的關係，因此可作為判斷距平降水分布的重要參考指標。

關鍵字

春梅雨季 ； 短期氣候 ； 區域氣候模式 ； 距平降水 ； 區域環流

並列摘要

Rainfall and associated circulation over the Eastem Asian on March to June, which is the spring and Mei-Yu rainfall season of Taiwan area, are examined in this study.
The NCEP regional spectral model(RSM) is used to provide four months long simulation during the experimental period and the selected years,1995 to 2001.In which initial conditions and base field were interpolated from the CWB global analyses and updated twice daily. GPCP monthly and 25 CWB observed data are use to evaluate the model precipitation on Eastern Asian(110E-130E,12N-35N)and Taiwan(120E-122E,22N-26N)area, and the simulated circulations are evaluated by CWB analyses.
Results of simulations show that model climate of this period are reasonable. One anti-clock wise anomalous circulation appeared on 850 hPa in both wet anomalous case of Eastern Asian and Taiwan, which is centered at South China and at East Sea separately. The positive rainfall anomaly in simulation is strongly associated with the westerly anomaly on the south side of the local circulation and the dry anomaly is within the easterly on the north side.
The detail and enhanced structure of rain band and local circulation are the effort of regional nested model. In some cases, model would cause systematical shift to the local circulation and then change the position of precipitation. It should be a seriously problem to the predictability of local area like Taiwan.

並列關鍵字

Spring and Mei-Yu season ； Short term climate ； Regional climate model ； Rainfall anomaly ； Local circulation