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題 名 | 夏季副熱帶高壓之年際震盪分析=Interannual and Interdecadal Variability of the Western North Pacific Subtropical High |
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作 者 | 鐘珮瑄; 隋中興; 李天明; | 書刊名 | 氣象預報與分析 |
卷 期 | 192 2007.09[民96.09] |
頁 次 | 頁40-46 |
分類號 | 328.3 |
關鍵詞 | 副熱帶高壓; |
語 文 | 中文(Chinese) |
中文摘要 | 分析1958-2005年NCEP/NCAR月平均再分析資料結果顯示,夏季北半球副熱帶高壓(簡稱副高)在西北太平洋地區的年際變化明顯,主要的變化週期為2-3年(準兩年)及3-5年。 副高的準兩年震盪在1980年之後出現頻率增加。較強副高所伴隨的夏季海溫分布類似La Nina發展期時特徵:中、東太平洋有較冷海溫,西太平洋海洋大陸一帶有較暖海溫。此分布導致較強對流與上升運動發生於暖海溫區,所產生之波動包括:局部哈得里環流,於臺灣東南方下沉,產生反氣旋距平,減弱西北太平洋季風,抑制當地對流;日本、 韓國一帶氣旋距平環流,增強日本南部的對流。 副高的3-5年震盪於1965-1990年間較顯著,夏季較強副高通常發生在E1 Nino減弱期,中、東太平洋有較暖海溫,其西北及東北二側有相伴之較冷海溫,延伸到西太平洋副熱帶地區。中、東太平洋的上升氣流往西北邊下沉,加上下墊面的較冷海溫,抑制局部對流,於臺灣東方產生反氣旋距平環流,此環流與中緯度西風帶相互作用,產生一連串的波列往北美洲傳播。 |
英文摘要 | This study analyzes the NECP/NCAR reanalysis data for the period of 1958-2005 to examine the interannual variability of the western North Pacific Subtropical High (WNPSH) in summer. The analysis reveals the WNPSH exhibits significant 2-3 years and 3-5 years oscillations with interdecadal variability. The 2-3-year oscillation is most evident after 1990. SST in the former (latter) region evolves from cold (weak warm) anomalies in the preceding summer to warm (cold) anomalies in the concurrent summer of strong WNPSH. The above change exhibits an eastward propagation, and is similar to the La Nina development. The stronger downward motion causes drier air and more outgoing longwave radiation. Such a heat balance maintains the anomalous high with equivalent barotropic vertical structure. The 3-5-year oscillation is most pronounced during the 1980s. The associated SST evolution is similar to that of El Nino with longer life cycle when WNPSH intensifies in the El Nino decaying summer. In the preceding summer, warm SST appears in the central-eastern Pacific, which is surrounded by cold SST to its north and south. The SST distribution persists till the concurrent summer of strong WNPSH. The complementary cooling and descending motion in the western Pacific are related to anomalous east-west circulation associated with ENSO. The anomalous WNPSH as part of the wave response exhibits baroclinic vertical structure. The analysis suggests that the 2-3-year oscillation is due to the monsoon-warn ocean interaction in the maritime continent, and the 3-5-year oscillation is related to the suppressed convection over the cold SST in the western North Pacific, causing Rossby wave response (anticyclonic flow) that is maintained by wind-evaporation-SST feedback mechanism. An intermediate atmopheric model which is forced by SST anomalies obtained from the analysis is used to further examine the above mechanisms. The model results support our mechanism for 3-5-year oscillation, but no clear evidence for 2-3-year oscillation. More model studies are required to investigate the relevant mechanism. |
本系統中英文摘要資訊取自各篇刊載內容。