东北冷涡及其气候影响

Cold Vortex over Northeast China and Its Climate Effect

基于自动识别、追踪方法得到的近50年东北冷涡数据集,本文研究了东北冷涡的年际变率及演变趋势,并分析了其持续性活动对我国气候的影响及相关联的大尺度环流异常特征。结果表明,东北冷涡具有很明显的年际变率,且存在2.5年左右的主振荡周期,但没有显著的长期变化趋势。东北局地在持续性冷涡控制下,四季气温均明显偏低,并在春季和夏季能造成局部降水偏多。在东北冷涡活跃的夏季,长江流域往往降水显著偏多;而在冬季东北冷涡频繁活动时,我国大部分地区往往低温少雨,这与强盛的东亚冬季风密切相关。研究结果表明,冬季东北冷涡活动和东亚冬季风强度之间的相关系数达到99%的信度水平。在东北冷涡活跃的夏季,东亚地区对流层维持着深厚的偶极型位势高度异常,高空急流向南偏移并略加强,低层西北太平洋反气旋异常和中纬度地区的东风异常有助于局地的水汽通量的辐合,进而有利于降水的偏多。

Based on the long-term dataset of cold vortex over Northeast China derived from automatic method of detection and track,interannual variability of cold vortex over Northeast China,the effect of its persistent activities on regional climate,and the associated large-scale circulation anomalies are investigated.The results show that the cold vortex has a considerable interannual variability,but no significant long-term trends.Persistent activities of cold vortex have a major oscillation with a period of about 2.5 a.Frequent occurrences of cold vortex can cause a significant negative air temperature anomaly over Northeast China for all seasons and lead to more local rainfall in spring and summer seasons.There are likely more rainfalls over the Yangtze River basin when the summer cold vortex is more frequent.In winter when the cold vortex occurs more frequently,most of China experiences lower air temperature and less rainfall,which is highly related to strong East Asian winter monsoon.In the summer of more cold vortices,deep dipole-like geopotential height anomaly maintains over East Asia,the upper-level jet stream shifts southward and is strengthened slightly,and the lower-tropospheric anticyclonic anomaly over the western North Pacific and the easterly anomaly over high latitudes facilitate the water vapor flux to be convergent over the Yangtze River basin and Northeast China,respectively.