2017年12月大气环流和天气分析

摘要

2017年12月大气环流的主要特征如下:北半球极涡呈偶极型分布,欧亚中高纬环流呈两槽一脊型;南支槽位于70°E附近,较常年同期偏西,副热带高压位置偏西,不利于水汽向我国中东部地区输送.12月,全国平均降水量为5.9 mm,比常年同期(10.8 mm)偏少44.8％,我国北方大部分地区降水量较常年同期偏少4～8成.全国平均气温-2.2℃,较常年同期(-3.2℃)偏高1℃;受偏强东北低涡影响,东北地区和内蒙古中东部气温较常年同期偏低1～～3℃.月内,冷空气活动频繁,但强度较弱,出现5次一般强度冷空气过程.受频繁冷空气影响,雾-霾天气较常年同期偏少,仅28 30日出现一次大范围持续性雾霾天气.%The main characteristics of the general atmospheric circulation in December 2017 are as follows.There were two polar vortex centers in the Northern Hemisphere.The circulation presented the trough-ridge-trough pattern in the middle-high latitudes of Eurasia.The south branch trough was located near 70°E,obviously more westward than that in the same period of normal years.Therefore,the location of the south branch trough was not favorable for the water vapor transport to eastern China.The subtropical high was located more westward than that in normal years.The monthly mean precipitation over China was 5.9 mm,which is 44.8％ less than the normal value (10.8 mm),especially for northern China,where precipitation amount decreased by 40％-80％ of the normal.The monthly mean temperature over China was-2.2℃,1℃ higher than the normal (-3.2℃).However,the temperature over northeastern China and the mid-eastern of Inner Mongolia was lower by 1-3℃ because of the strong east major trough.There were five cold air processes,which were not as strong as the normal events but more active than the normal.These active cold airs led to less fog-haze weather,and only one fog-haze period which occurred from 28 to 30 December 2017.