北极涛动对冬季北京极端低温事件的影响分析

Influence Analysis of Arctic Oscillation on Extreme Cold Events in Beijing

根据1951-2009年冬季北京观象台逐日最高、最低气温资料和NCAR/NCEP逐日海平面气压、500hPa高度再分析资料,分析了冬季北极涛动(Arctic Oscillation,简称AO)对北京极端低温事件的影响。结果表明,近59 a冬季北极涛动指数与北京极端低温事件显著负相关,有56.7%(57%)的冷夜(冷日)发生在月AO负异常时期,仅17%(20.7%)的冷夜(冷日)发生在月AO正异常时期。进一步分析表明,当AO负位相时,北京地区冷空气暴发的关键系统容易发展,即对流层中层欧亚北部地区易出现阻塞形势,低层西伯利亚高压增强发展。

Using Beijing meteorological station daily surface maximum and minimum temperature data and NCAR/NCEP daily sea level pressure and 500 hPa height reanalysis data from December 1st 1951 to February 28th 2010,the relationship between Arctic Oscillation and extreme cold events in Beijing are investigated.Correlation analysis for the last 59 winters shows that frequency of the extreme cold events in Beijing changes out of phase against AO.56.7% and 57% of cold nights and cold days are prone to onset during abnormal negative periods of AO separately,while only 17% and 20.7% of cold nights and cold days break up during abnormal positive periods of AO separately.Under the negative phase of AO,the key systems for cold-air outbreak in Beijing develop,when blocking situation over the northern part of the Eurasian continent is more to happen on the 500 hPa,and the Siberian high strengthens at sea level pressure.