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題 名 | 夏季西北太平洋副高年際變化機制之研究=A Study on the Interannual Variation of Northwestern Pacific Subtropical High in Summer |
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作 者 | 呂芳川; 郭漱泠; 陳昭銘; | 書刊名 | 大氣科學 |
卷 期 | 34:1 民95.03 |
頁 次 | 頁25-45 |
分類號 | 328.3 |
關鍵詞 | 西北太平洋副熱帶高壓; 海溫異常對比; 羅士培波源; 南海海溫; 聖嬰與反聖嬰現象; 海氣交互作用; Northwestern Pacific subtropical high; SST anomaly contrast; Rossby wave response; E1 Niño; La Niña; |
語 文 | 中文(Chinese) |
中文摘要 | 西北太平洋副熱帶高壓是夏季時甚受矚目的環流,具有相當強的年際變異訊號,本文使用自 1978至2002年的NCEP/NCAR重分析資料分析驅動西北太平洋副熱帶高壓異常增強的機制,再進步釐清海溫所扮演的角色。為了能清晰地表現人氣熱動力結構,本文以區間(10°-30°N,100°-150°E)的平均850mb流函數駐留渦流場距平並標準化後定義為西北太平洋副熱帶高壓強度指標 (WPI)。 本文利用合成分析法探討與西北太平洋副熱帶高壓強度年際變化相關的環流特性、海溫與對流系統,認為維持西北太平洋副熱帶高壓強度異常發展有兩個主要機制,一個是以約140°E為界的大尺度東西向海溫距平對比調變的沃克環流,造成大尺度非絕熱熱源(匯)的偏西發展,因羅士培波源響應導致西北太平洋副熱帶高壓反氣旋渦度的增強,另個機制是90°E-140°E間約以10°N為界的南多北少的降水差異,這種區域性哈德雷環流的調變,提供了西北太平洋副熱帶高壓強度異常發展的質量平衡。 考慮海溫與大氣非絕熱熱源,以夏季為中心的動態分析顯示,四月至五月間,近赤道西北太平洋海域與南印度洋海域的海溫變異在各自海域的大洋動力影響下獨立發展,兩者海溫距平對比偶合的強度與夏季時西北太平洋副熱帶高壓發展強度密切相關。在WPI偏高年的春末夏初時,配合反聖嬰(La Niña)的開始發展,熱帶東太平洋海溫變涼,印度洋海溫偏暖,調變的熱源將導引羅士培波源響應,有利於西北太平洋副熱帶高壓所在位置的反氣旋渦度的發展發展中的反氣旋東南端有東北風異常輸送較冷的海水,南側的東風異常導致的湧升流將進步使赤道中至東太平洋的海水變冷,使得大尺度的東西向海溫差異對比加強,對西北太平洋副熱帶高壓的異常發展有正回饋的作用,又進而有利於東太平洋海溫的變冷,也就是說夏季西北太平洋副熱帶高壓的反氣旋異常環流與反聖嬰現象的發展兩者互相回饋;在WPI偏低年則有相反的結果。 |
英文摘要 | The relationship between the western north Pacific subtropical high (WNPSH) and the related SST anomaly is studied using NCEP reanalysis data from 1978 to 2002. In order to clarify the thermodynamic mechanism for WNPSH anomaly, we define the normalized anomaly of the average intensity of 850mb stream function over the region (10°-30°N, 110°-150°E) as index WPI to indicate the intensity of WNPSH. In this study, it is shown that there are two mechanisms to maintain WNPSH anomaly. First, the large-scale west-east SST anomaly contrast in tropics, which could be represented by Nino3.4 SST, will modulate the Walker circulation and enhance anticyclone anomaly by Rossby wave response. Second, the modulated local Hadley cell is needed for mass balance as WNPSH enhanced. Considering SST forcing and heat budget, the analysis shows that the vigorous WNPSH anomaly is originated two months before summer. The intensity of SST anomaly contrast between western Pacific and Indian Ocean during April and May is closely related to the intensity of the WNPSH anomaly in summer. Also, the anticyclone is excited by the large-scale west-east SST anomaly contrast in tropics via Rossby wave response. Because the cool water is driven to central to eastern Pacific by friction drag of the enhanced easterly and northeasterly anomaly over the rare of WNPSH, the cold episodes is favorable to develop and, in turn, the large-scale SST anomaly contrast gives the positive feedback to enhance the anticyclone anomaly. |
本系統中英文摘要資訊取自各篇刊載內容。