2012年欧亚寒冷天气过程与北极涛动异常活动的联系

THE LINKAGE BETWEEN THE COLD WEATHER PROCESS OVER EURASIAN CONTINENT AND THE ABNORMAL ACTIVITY OF THE ARCTIC OSCILLATION IN 2012

利用NCEP/NCAR再分析资料和CPC逐日北极涛动(AO)指数资料,结合近30年欧亚地区地面气温年际异常变化的可能机理,分析了AO异常波动对2012年欧亚地区严寒天气过程的影响。结果表明,AO发生负异常波动对2012年1—2月欧亚地区异常寒冷天气起到至关重要的作用。AO在12月为正异常波动,次年1—2月则呈现负异常波动,其中1月中下旬至2月中旬的负异常波动过程比较显著。在AO负异常影响下,极涡面积增大,冷空气活动加强,中纬度纬向环流减弱而经向环流增强,造成冷、暖空气交换加剧,极地冷空气南下入侵到中纬度地区,从而导致欧亚大陆异常寒冷天气;同时,由北大西洋及地中海北上的暖湿气流,在遭遇冷空气阻碍后给西欧和南欧一些地区带来了大面积的雨雪天气。

In combination with the possible mechanism of surface temperature anomalies over Eurasian ground in nearly 30 years, the NCEP/NCAR reanalysis data and CPC daily Arctic Oscillation （AO） index material are used to analyze the influence of AO unusual fluctuation on the cold weather process over Eurasian continent in 2012. The results show that the negative AO abnormal fluctuation plays a key role in the cold weather process over Eurasian continent from January to February in 2012. AO abnormal fluctuation is positive in December last year, while negative in January and February next year. From the mid-late ten days of January to the middle ten days of February, the negative abnormal fluctuation is significant. AO negative＇ abnormal fluctuation increases the polar vortex area, strengthens the cold air activity, decreases the mid-latitude zonal circulation and enhances the meridional circulation, which intensify the exchanges between cold and warm air, and result in polar cold air to invade to the mid-latitude area, eventually, cause the unusual cold weather in Eurasia. Meanwhile, after being obstructed by cold air, the warm and moist southerly from north Atlantic and Mediterranean brought large-area rain and snow over western and southern Europe.