西北太平洋地區颱風活躍度分析：活躍年和不活躍年比較

Examining Typhoon Activity in the Western North Pacific: Difference between Active and Non-Active Years

邱品竣(Pin-Gin Chiu) ； 余嘉裕(Jia-Yuh Yu)

《大氣科學》 34卷3期 (2006/09) Pp. 201-215

摘要

文利用1965~2003年JTWC所提供之颱風資料以及NCEP/NCAR大氣資料，探討西北太平洋地區颱風活動與背景大氣問之關係，並藉由累積颱風動能作為颱風活躍度指標以比較颱風活躍年和不活躍年差異。由於累積颱風動能考慮了颱風強度和持續時間，比颱風生成個數更能反映出實際颱風活躍度變化。
研究結果顯示，西北太平洋颱風活躍度和西北太平洋副熱帶高壓、Walker環流、低層跨赤道氣流三個大氣因素有關，三者並有顯著的動力連結。副熱帶高壓變化與赤道太平洋異常大氣環流結構有密切關係，在颱風活躍（不活躍）年時，異常Walker環流在東太平洋上升（下沈），西太平洋下沈（上升），其中由於西太平洋下沈（上升）中心偏向南半球，激發低層跨赤道南風（北風），增強（減弱）西北太平洋地區水氣輻合，加強（減弱）季風槽範圍和強度，有利（抑制）颱風發展。簡言之，欲加強西北太平洋颱風季節預報能力可由掌握副熱帶高壓、Walker環流、低層跨赤道氣流三個大氣因素的變化來加以提升。

關鍵字

颱風 ； 颱風活躍度

並列摘要

In this paper, JTWC best track data of Typhoon and NCEP/NCAR atmospheric data are employed to examine relation between Typhoon activity in the Western North Pacific (WNP) and the associated background atmospheric circulation. The so-called ”accumulated wind energy” of Typhoon is used to characterize Typhoon activity. Since the accumulated wind energy considers the strength and duration of each Typhoon, it can represent Typhoon activity more realistically compared to the total number of Typhoon genesis.
Our study indicates that three factors, which are dynamically linked to each other, can affect Typhoon activity: Subtropical Pacific High (SPH), Walker circulation, and cross-equatorial flow. We note that variation of the SPH is closely associated with anomalous atmospheric patterns in the equatorial Pacific. In the active (inactive) years, anomalous Walker Circulation ascends (descends) in the eastern Pacific while descends (ascends) in the western Pacific. Since the descending (ascending) center tends to bias to Southern Hemisphere, it results in cross-equatorial southerlies (northerlies) in the western Pacific and enhancing (weakening) moisture convergence in the Monsoon trough. This situation is found to favor (disfavor) Typhoon activity in the WNP. In summary, an improved prediction of seasonal Typhoon activity in the WNP can be accomplished by knowing well the variation of SPH, Walker Circulation, and cross-equatorial flows.

並列關鍵字

Typhoon ； Typhoon activity