北大西洋涛动对新疆冬季极端冷事件的影响

利用1961—2016年新疆各站逐日气温、NCEP再分析高度场、风场资料及北大西洋涛动（NAO）指数，分析了新疆1961—2016年冬季出现的极端冷事件频次变化及与其相联系的环流特征。冬季NAO通过欧亚（EU）波列传播影响新疆冬季极端冷事件的变化，但冬季NAO位相与新疆冬季极端冷事件并没有逐年一一对应的负相关关系。在冬季NAO负位相年，由EU波列传播，70°N以北北风偏弱，当乌拉尔山及其以东区域位势高度偏高（低），50°~70°N西风偏弱（强）时，新疆冬季极端冷事件偏多（少）；在冬季NAO正位相年，由EU波列传播，70°N以北北风偏强，当乌拉尔山及其以东区域位势高度偏高（低），50°~70°N西风偏弱（强）时，新疆冬季极端冷事件偏多（少）。因此，冬季NAO、乌拉尔山及其以东区域高度场和50°~70°N西风三者共同作用决定了新疆冬季极端冷事件的发生频次，其中乌拉尔山及其以东区域位势高度和50°~70°N西风在冬季NAO对新疆极端冷事件的影响关系中起到了重要的调制作用。

Effects of NAO on the Extreme Cold Events in Xinjiang in Winter

The frequency and circulation of extreme cold events in Xinjiang in winter were analyzed based on the daily air temperature data from the meteorological stations in Xinjiang,NCEP reanalysis data of the height field,wind field,temperature field and North Atlantic Oscillation (NAO) index during the period of 1961-2016. The variation of extreme cold events in Xinjiang in winter was affected by the Eurasia (EU) wave train transmission,in winter,however,there was no one to one corresponding negative correlation between the NAO phase and the extreme cold events in Xinjiang in winter. In the winter of NAO negative phase,NAO was spread by the EU wave train,and the north wind was weak in north of 70°N. Under this background,the extreme cold events in Xinjiang in winter were more (less) when the geopotential height over the Ural Mountain and its east region was high (low) and the west wind was weak (strong) in 50°-70°N. In the winter of NAO positive phase,NAO was spread by the EU wave train,and the north wind was strong in north of 70°N. Under this background,the extreme cold events in Xinjiang in winter were more (less) when the geopotential height over the Ural Mountain and its east region was high (low) and the west wind was weak (strong) in 50°-70°N. The result showed that the occurrence frequency of extreme cold events in Xinjiang was mainly affected by the interaction of NAO,the geopotential height field over the Ural Mountain and its east region and the west wind in 50°-70°N,of which,the west wind in 50°-70°N in winter and the geopotential height field over the Ural Mountain and its east region were the main affecting factors.