- 學位論文
2010東歐夏季熱浪的診斷與模擬
On the 2010 Anomalous Europe Blocking High and Wave Activity
摘要
在2010年的夏天，東歐發生了俄羅斯熱浪，造成一萬多人死亡以及嚴重的經濟損失，屬於相當極端的熱浪。熱浪起因於在東歐影響整個夏季之阻塞高壓，噴流位置的改變也使的非洲的暖空氣容易進入東歐，創下高溫紀錄。此高壓在長期的百分位數上非常突出，因大氣提供良好的條件使阻塞生成及維持，分析後發現2010年瞬變渦流活動情形明顯，不僅阻塞上游渦流活躍，阻塞下游的活動情形更是突出，也顯示阻塞影響的範圍涵蓋整個歐亞大陸，瞬變渦流的活躍反映在能量轉換上，在阻塞上游能量由瞬變渦流轉換至平均流的情形顯著，E向量分析上也顯示這些能量輻合到阻塞區累積，使得阻塞有足夠的能量長期維持。而在駐波能量通量上則發現由北美及大西洋向東頻散的波列，並且在垂直上面發現顯著的由低層向高層頻散之通量，在阻塞發生處輻散，分成兩支向下游東南及東北方頻散，顯示能量可能來源除了北美及大西洋方向外，也有來自低層地表或海洋的作用。 這樣極端的阻塞現象，雖然有良好的大氣條件，但必有其他因素影響才可能發生，本研究目的為了解此極端現象之相關的因素，企圖找出維持阻塞長期籠罩東歐之影響因素，故由海溫著手，探究是否高海溫維持了此阻塞高壓，並利用ECHAM5模式做檢驗。 2010年的海溫有幾處相當的高，尤其是鄰近歐洲的熱帶、高緯度大西洋以及印度洋，皆超過95百分位數，以此海溫距平作為邊界驅動大氣環流模式，三實驗皆可以在東歐地區產生正的壓力距平，但程度遠小於實際情形，瞬變渦流與平均場的交互作用情形微弱，在大西洋兩實驗中，能量進入波導引發類似的波列，印度洋的實驗可能經由羅士培波源的引發，引發高壓及影響波列傳送。 本研究以大氣環流模式探究海溫對於東歐阻塞高壓的貢獻，結果顯示不論是大西洋海溫或者印度洋海溫，皆對東歐阻塞高壓有加強的貢獻，且印度洋的影響較大西洋來的強烈，但無法在模式中得到如實際般的極端情形。長期統計分析顯示東歐阻塞與熱帶大西洋和高緯大西洋海溫呈現顯著正相關，表示海溫是造成東歐擾動的重要因素，但2010年個案的極端強度則不是極端海溫異常可以單獨解釋。
並列摘要
A series of severe heat waves, wildfires and droughts occurred in Eastern Europe in the 2010 summer. This dramatic event is also known as the 2010 Russian heat wave. Over 15,000 people lost their life in this event, and the economic loss was dramatic. A long-lasting blocking high that affected this region between June 20th and August 16th. The percentile analysis showed the 500hPa pressure in the region was the highest among the past 53 summers. Meanwhile, the sea surface temperature (SST) in parts of the North Atlantic was also found to be among the highest in the past 130 years. The possible effect of the anomalously high Atlantic SST anomaly (SSTA) on the Eastern European blocking high was explored in this study using the ECHAM5 AGCM. Different initial conditions and resolutions were first tested in the simulations forced by the observed global SSTA. The observed high SSTA in the tropical and high-latitude Atlantic were prescribed as forcing to explore their relative influence. The results were sensitive to both the spatial resolution and initial condition. The T106 simulations with proper initial conditions were able to produce reasonable results, while all T63 simulations with or without proper initial condition failed to simulation the event. Both tropical and high-latitude SSTA experiments reasonably simulated the high-pressure anomaly in the Eastern Europe, however, the high-latitude SSTA experiment performed slightly better than the tropical SSTA one. The wave activity flux calculated from the model output showed that both SSTA experiments carried energy flux into waveguide. Thus, the pattern that simulated performed analogously. India Ocean SSTA were also anomalous high in 2010 summer. The effect of the high SSTA was tested by same condition. The India ocean SSTA experiment may induce Rossby wave source near Mediterranean that cause a resembling wave pattern near East Europe. The result showed India ocean SSTA had more effect then the Atlantic SSTA. The preliminary results suggest that the anomalously high SSTA in the Atlantic and India ocean could be partially responsible for the European blocking in the 2010 summer. However, the simulated amplitudes are smaller the observed. Such an experiment approach cannot explain the record-breaking amplitude and duration of this unusual event.
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