中国北方暴雪的年代际变化及其与大气环流和北极海冰的联系

采用相关、回归等统计方法,对中国北方暴雪的年代际变化特征及其与大气环流和北极海冰的联系进行探讨。结果表明:中国北方冬季暴雪发生频次较高区域主要位于东北,在空间分布上呈现由西北向东南增加的态势,且存在明显的年代际变化特征:1965—1980年为东北暴雪少发期; 2002—2011年为东北暴雪多发期。分析表明:暴雪少发期,输送至东北的水汽较少;暴雪多发期,更多的水汽输送来自于西北太平洋,同时偏北气流引导的极地冷空气与偏南风引导的太平洋暖湿空气在东北地区汇合,提供暴雪频发的动力条件,造成东北暴雪出现年代际增多。此外,研究发现:前期秋季北极海冰的年代际减少与东北暴雪的年代际增加存在很好的相关性;秋季北极海冰异常偏少导致的大气环流异常主要表现为纬向西风减弱和NAO负位相,由此导致大气经向活动增强,利于极地冷空气向南入侵,且冷空气与暖湿空气在东北地区汇合,这是东北暴雪年代际增加的重要原因之一。

Interdecadal variation of heavy snowfall in northern China and its linkages with atmospheric circulation and Arctic sea ice

This study explored interdecadal variation of heavy snow in northern China and its relationship with atmospheric circulation and Arctic sea ice by using statistical methods such as correlation and regression.Results show that the high frequencies of heavy snow in northern China in winter are mainly located in Northeast China (NEC),and its spatial distribution shows an increasing trend from northwest to southeast,together with obvious interdecadal variations.Heavy snowfall in NEC is less during 1965-1980,but more during 2002-2011.Analysis shows that there is less water vapor transported to NEC during 1965-1980,but more water vapor transported from Northwest Pacific to NEC during 2002-2011.Meanwhile,the cold polar air guided by northerly airflow and Pacific warm moisture transport guided by southerly airflow benefit a convergence frontogenesis in NEC,providing favorable dynamic conditions for the frequent occurrence of heavy snow,and leading to the interdecadal increase of heavy snow in NEC.Furthermore,it is found that there is a close linkage between the interdecadal decrease of Arctic sea ice in early autumn and the interdecadal increase of snowstorm in NEC.Anomalous circulation pattern caused by the decreased Arctic sea ice in autumn shows that the zonal westerly decreases and NAO is in the negative phase,which can intensify atmospheric meridional activity and be conducive to the southward invasion of polar cold air,leading to the convergences of cold air and warm moist air in NEC.This is a possible important reason for the interdecadal increase of heavy snow in NEC.