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    請使用永久網址來引用或連結此文件: http://ir.lib.ncu.edu.tw/handle/987654321/5019


    題名: 北極震盪(Arctic Oscillation, AO)對東亞地區氣候系統影響之研究
    作者: 楊竣凱;Chun-kai Yang
    貢獻者: 大氣物理研究所
    關鍵詞: 北極震盪;Arctic Oscillation
    日期: 2008-06-27
    上傳時間: 2009-09-22 09:43:10 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 本研究除了要探討,在北極震盪(Arctic oscillation, AO)相位影響下,東亞地區氣候系統的變化與其影響,也藉由AO與其他氣候系統如ENSO的交互作用,進一步瞭解其對東亞地區的影響。研究方法主要是利用合成的環流場和EOF分析,來了解其氣候特徵。使用的資料為ERA-40各氣象場和CRU的降水資料,以及NCEP-NCAR reanalysis(R1)各氣象場與GPCP的降水場。 結果發現,AO暖相位時,西伯利亞高壓減弱造成東亞沿岸有西南風距平,以及阿留申低壓減弱導致西太平洋上有西風距平,此距平會將暖濕空氣帶入東亞地區。在中對流層有高度正距平位於日本一帶,此距平西側有利於斜壓擾動的發展(脊之西邊有利於斜壓擾動)。在水氣多且斜壓擾動加強的情況下,東亞沿岸降水的機會就會增加。AO冷相位時,雖然中對流層的東亞主槽會加強,但是西伯利亞高壓加強會將乾冷空氣帶至東亞沿岸,且西太平洋有低壓距平導致暖濕空氣不會進入東亞地區,進而不利東亞沿岸地區的降水。 ENSO暖事件時,西伯利亞脊減弱導致西伯利亞高壓跟著減弱,中國大陸低層會出現壓力負距平。另外,中對流層的東亞主槽北移,最後導致下對流層的西太平洋有壓力正距平。中國大陸的低壓距平和西太平洋的壓力正距平,會導致東亞沿岸有西南風距平並帶來暖濕空氣,此時東亞沿岸降水機會就會增加。反之亦然。 由氣候特徵之間的交互作用個案,可以發現AO和ENSO兩者的特徵皆會存在於各氣象場,且會產生相互影響。由溫度場分析發現,中緯度地區(35°N-60°N,115°E-150°E)是受AO所控制,而副熱帶地區以南(5°N-30°N,60°E-110°E)是受ENSO所影響。從海平面氣壓發現,在AO冷相位和ENSO冷事件的個案中,下對流層的西伯利亞高壓加強最多。在風場發現,只要是AO暖相位時,無論是和ENSO冷、暖事件的交互作用個案,在西太平洋會有東風距平。AO冷相位和ENSO暖事件在各別影響時,都會導致東亞主槽加強,在兩事件同時發生的個案中,發現東亞主槽加強最顯著。 比較2008年中國雪災(AO暖事件與ENSO冷事件)和交互作用的個案(AO暖事件與ENSO冷事件)氣候特徵的差異發現,雪災的發生可能是和中對流層在巴爾喀什湖有高度負距平,下對流在菲律賓一帶有壓力負距平有關,而這些現象也代表交互作用下個案與2008年的個案在氣候特徵上是個案之間的差異。最後,中國大陸雪災的發生可能跟ENSO冷事件有相當程度的關係。將含有兩年的交互作用個案分開討論,發現各氣象場和降水場有相當的一致性,這也代表交互作用的影響與存在是有利於瞭解氣候特徵的價值。 This study focus on climate systems variation due to Arctic Oscillation and its effect in East Asia, and the impact of the interaction of the Arctic Oscillation and the ENSO on East Asia climate. The analysis methods are composite analysis and EOF analysis. The data used are various meteorological fields from ERA-40 and CRU, and from NCEP-NCAR reanalysis (R1) and GPCP data for 2008. In the AO warm phase, the results show that the Siberian High is weaker which results in southwesterly anomaly in East Asia, the Aleutian Low becomes weaker too which induces westerly anomaly in West Pacific coastal region. The westerly anomaly brings warm and humid air into East Asia. There is positive geopotential height anomaly in mid-troposphere over the Japan area. Consequently, there is a positive anomaly of baroclinic disturbance in East Asia. There is a positive precipitation anomaly in East Asia due to humid air and more baroclinic disturbance. In the AO cold phase, the Siberia High is enhanced that brings dry and cold air into East Asia. There is negative pressure anomaly in West Pacific Ocean that causes low warm and humid air in East Asia. This situation results in reduction of precipitation in East Asia. In the ENSO warm case, the Siberia High becomes weaker in the lower-troposphere due to the weakening of Siberia ridge in the mid-troposphere. Consequently, there is a negative pressure anomaly in China area. The east Asian main trough shifts to the north in the mid-troposphere. This situation causes positive pressure anomaly in the West Pacific Ocean. Negative pressure anomaly in China and positive pressure anomaly in the West Pacific Ocean intensify southwesterly anomaly, so that warm and humid air come to East Asia. Therefore, there is a positive precipitation anomaly in East Asia. The ENSO cold case is an opposite phenomenon. Compare 2008 China snow disaster case (AO warm phase and ENSO cold phase) with cases of 1976 and 2000 under the same climate condition. The result shows that the features are different between the case of 2008 and the former cases. However ENSO cold phase affect on China snow disaster more than AO warm phase.
    顯示於類別:[大氣物理研究所 ] 博碩士論文

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