冬季北大西洋濤動（NAO）的變異及其對歐洲天氣的影響機制研究
發(fā)布時間：2018-11-21 08:06
【摘要】：北大西洋濤動（North Atlantic Oscillation簡稱：NAO）是北半球冬季最顯著的大氣低頻偶極子模態(tài)。NAO對局地及周邊地區(qū)的天氣氣候有著顯著的調控作用。已有的大部分的研究主要是關注NAO氣候態(tài)的平均特征（月平均，季節(jié)年平均），但是并不能刻畫每個NAO事件生命過程的具體變化特征，因此也無法研究NAO生命過程對歐洲天氣的影響，尤其是對低溫降雪天氣的影響機制。另外，對于時空變異的NAO事件來說，傳統(tǒng)的NAO正、負位相（NAO+和NAO-）的分類方法并不能完全刻畫其特征。本文針對上述問題，從NAO生命周期分解和NAO事件變異兩個主要方面進行了系統(tǒng)的研究。具體結論如下： 本文通過將NAO生命過程詳細分解為開始階段（B1），發(fā)展階段（B2），衰減階段（A1）及結束階段（A2）四個關鍵期，分析了不同生命階段對應的歐洲地區(qū)阻塞、溫度及降水的分布變化。合成分析發(fā)現(xiàn)，阻塞分布明顯受到NAO位相的調控作用。受NAO+事件調控，阻塞從大西洋東部至歐洲東北部呈現(xiàn)西南－東北（SW-NE）方向分布；受NAO-事件調控，阻塞從歐洲中部至北大西洋和格陵蘭地區(qū)呈現(xiàn)東南－西北（SE-NW）方向分布。特別發(fā)現(xiàn)，在NAO+（NAO-）事件生命周期中，對應的升溫（降溫）最明顯的階段為衰減階段，這主要是由于溫度平流對歐洲大陸的延遲影響導致的。物理機制分析發(fā)現(xiàn)，NAO-（NAO+）階段北歐（南歐）阻塞頻率的增加與NAO-（NAO+）偶極子結構的西退（東移）密切相關。大西洋中高緯度西風的減弱（加強）與NAO偶極子結構的緯向西退（東移）密切相關，即NAO過程的自我反饋機制。 圍繞2012年1月～2月歐洲地區(qū)發(fā)生的一次極端低溫（暴雪）事件，結合最近提出的原地型（In-situ）和位相轉換型（Transition）NAO事件的分類，指出發(fā)生位置變異的偏東型位相轉換事件（NAO+轉Eastern NAO-簡稱： NAO+轉ENAO-）的發(fā)生有利于歐洲爆發(fā)低溫降雪天氣過程。ENAO-事件會給整個歐洲地區(qū)尤其是東歐和南歐帶來大幅度持續(xù)的降溫過程，同時在ENAO-環(huán)流所對應的南北分支風暴路徑的調控作用下，南歐降水（雪）增多。 進一步的氣候統(tǒng)計分析表明，雖然NAO+（NAO-）會給歐洲帶來升溫（降溫）過程，同時降水分布表現(xiàn)為單支（南北兩支）結構，但是NAO事件緯向位置的變異會給歐洲地區(qū)的天氣氣候造成不同的影響。本文中，以NAO偶極子中心的北部中心為標準，判斷其位置處在10W經線以東和以西來劃分偏東型NAO（EasternNAO簡稱：ENAO）和偏西型NAO（Western NAO簡稱：WNAO）事件。分析表明，不論對于In-situ NAO-事件還是Transition NAO-事件，ENAO－給歐洲地區(qū)帶來的降溫幅度和面積要大于WNAO-。另外發(fā)現(xiàn)在2005年之后，NAO+轉ENAO-事件發(fā)生的頻率明顯增多，，可能是近10年歐洲地區(qū)頻發(fā)極端寒冷暴雪天氣的原因。進一步的分析發(fā)現(xiàn)，相比WNAO+事件，ENAO+事件會給歐洲帶來更加明顯的升溫作用。同時，ENAO事件對應的阻塞的分布位置也相對偏東。NAO的緯向位置與西風強弱有密切關系，較強的西風會強迫NAO向下游（東）發(fā)展變異；如果西風偏弱，NAO位置就會相對偏西。
[Abstract]:The North Atlantic Treaty (NAO) is the most significant low-frequency dipole modality in the northern hemisphere. The NAO has a significant regulatory effect on the weather and climate in the local and surrounding areas. Most of the studies have focused on the average (monthly, seasonal, average) characteristics of the NAO climate state, but it is not possible to describe the specific change characteristics of the life process of each NAO event, so it is not possible to study the effect of the NAO life process on the European weather. in particular to a mechanism for influencing the low-temperature snowfall weather. In addition, the traditional NAO positive and negative phase (NAO + and NAO-) classification methods do not completely characterize the NAO events of space-time variation. In the light of the above-mentioned problems, the research of the system is carried out from the two main aspects of the NAO life cycle decomposition and the NAO event variation. The specific conclusions are as follows: In this paper, through the detailed breakdown of the NAO life process into four key periods of the start stage (B1), the development stage (B2), the attenuation stage (A1) and the end stage (A2), the distribution of the obstruction, the temperature and the precipitation in the European region corresponding to the different life phases is analyzed. The results of synthesis and analysis show that the blocking distribution is obviously affected by the control of the NAO phase. The function is controlled by the NAO + event, blocking the distribution of the southwest-northeast (SW-NE) direction from the eastern part of the Atlantic to the north-east of Europe, and is controlled by the NAO-event to block the direction of southeast-northwest (SE-NW) from the central part of Europe to the North Atlantic and Greenland. Distribution. In particular, in the life cycle of the NAO + (NAO-) event, the most obvious phase of the corresponding temperature rise (cooling) is the attenuation stage, which is mainly due to the influence of the temperature advection on the European continent's delay. The physical mechanism analysis shows that the increase of the blocking frequency of the NAO-(NAO +) phase in the Northern Europe (NO +) phase is close to that of the NAO-(NAO +) dipole structure. Correlation between the weakening (strengthening) of the high-latitude westerly wind in the Atlantic and the weft-to-west (east-shift) of the NAO dipole structure, that is, the self-feedback of the NAO process Mechanism. An extreme low temperature (Blizzard) event that occurred in the European region from January to February 2012, in combination with the recent classification of In-situ and Transition NAO events, it was noted that the east-type bit-phase transition event (NAO + to Eastern N, The occurrence of AO-abbreviation: NAO + (NAO-) is beneficial to the low temperature drop in Europe The process of snow and weather. The ENAO-event will bring a significant and sustained cooling process to the whole European region, especially in Eastern Europe and Southern Europe, while the south-European precipitation is under the control of the north-south branch storm path corresponding to the ENAO-circulation. (snow) increased. The further analysis of climate statistics shows that while NAO + (NAO-) will bring a temperature rise (cooling) process to Europe, the precipitation distribution is shown as a single branch (both north and south), but the variation of the weft-to-position of the NAO event will give the weather gas in the European region In this paper, the north center of the center of the NAO dipole is used as the standard, and the position is determined to be east and west of the 10W warp, and the Eastern NAO and the Western NAO (Western NAO) are divided.: WNAO) events. The analysis shows that, whether for In-situ NAO-event or transition NAO-event, the temperature drop and area of the ENAO-to the European region To be greater than the WNAO-. It is also found that, after 2005, the frequency of NAO + to ENAO-events has increased significantly and may be the most frequent extreme cold in the European region in the last 10 years The reason for the cold snowstorm is that the ENAO + event will bring more to Europe than the WNAO + event. Add a significant temperature rise effect. At the same time, the ENAO event corresponds to a blocked score The position of the cloth is also relative to the east. The latitude position of the NAO is closely related to the strength of the westerly wind. The stronger westerly wind forces the NAO to develop the variation to the downstream (east); if the westerly wind is weak, the NAO
【學位授予單位】：中國海洋大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：P461.2;P732
本文編號：2346397
[Abstract]:The North Atlantic Treaty (NAO) is the most significant low-frequency dipole modality in the northern hemisphere. The NAO has a significant regulatory effect on the weather and climate in the local and surrounding areas. Most of the studies have focused on the average (monthly, seasonal, average) characteristics of the NAO climate state, but it is not possible to describe the specific change characteristics of the life process of each NAO event, so it is not possible to study the effect of the NAO life process on the European weather. in particular to a mechanism for influencing the low-temperature snowfall weather. In addition, the traditional NAO positive and negative phase (NAO + and NAO-) classification methods do not completely characterize the NAO events of space-time variation. In the light of the above-mentioned problems, the research of the system is carried out from the two main aspects of the NAO life cycle decomposition and the NAO event variation. The specific conclusions are as follows: In this paper, through the detailed breakdown of the NAO life process into four key periods of the start stage (B1), the development stage (B2), the attenuation stage (A1) and the end stage (A2), the distribution of the obstruction, the temperature and the precipitation in the European region corresponding to the different life phases is analyzed. The results of synthesis and analysis show that the blocking distribution is obviously affected by the control of the NAO phase. The function is controlled by the NAO + event, blocking the distribution of the southwest-northeast (SW-NE) direction from the eastern part of the Atlantic to the north-east of Europe, and is controlled by the NAO-event to block the direction of southeast-northwest (SE-NW) from the central part of Europe to the North Atlantic and Greenland. Distribution. In particular, in the life cycle of the NAO + (NAO-) event, the most obvious phase of the corresponding temperature rise (cooling) is the attenuation stage, which is mainly due to the influence of the temperature advection on the European continent's delay. The physical mechanism analysis shows that the increase of the blocking frequency of the NAO-(NAO +) phase in the Northern Europe (NO +) phase is close to that of the NAO-(NAO +) dipole structure. Correlation between the weakening (strengthening) of the high-latitude westerly wind in the Atlantic and the weft-to-west (east-shift) of the NAO dipole structure, that is, the self-feedback of the NAO process Mechanism. An extreme low temperature (Blizzard) event that occurred in the European region from January to February 2012, in combination with the recent classification of In-situ and Transition NAO events, it was noted that the east-type bit-phase transition event (NAO + to Eastern N, The occurrence of AO-abbreviation: NAO + (NAO-) is beneficial to the low temperature drop in Europe The process of snow and weather. The ENAO-event will bring a significant and sustained cooling process to the whole European region, especially in Eastern Europe and Southern Europe, while the south-European precipitation is under the control of the north-south branch storm path corresponding to the ENAO-circulation. (snow) increased. The further analysis of climate statistics shows that while NAO + (NAO-) will bring a temperature rise (cooling) process to Europe, the precipitation distribution is shown as a single branch (both north and south), but the variation of the weft-to-position of the NAO event will give the weather gas in the European region In this paper, the north center of the center of the NAO dipole is used as the standard, and the position is determined to be east and west of the 10W warp, and the Eastern NAO and the Western NAO (Western NAO) are divided.: WNAO) events. The analysis shows that, whether for In-situ NAO-event or transition NAO-event, the temperature drop and area of the ENAO-to the European region To be greater than the WNAO-. It is also found that, after 2005, the frequency of NAO + to ENAO-events has increased significantly and may be the most frequent extreme cold in the European region in the last 10 years The reason for the cold snowstorm is that the ENAO + event will bring more to Europe than the WNAO + event. Add a significant temperature rise effect. At the same time, the ENAO event corresponds to a blocked score The position of the cloth is also relative to the east. The latitude position of the NAO is closely related to the strength of the westerly wind. The stronger westerly wind forces the NAO to develop the variation to the downstream (east); if the westerly wind is weak, the NAO
【學位授予單位】：中國海洋大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：P461.2;P732
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