2016年1月京津冀地区连续性寒潮事件对比分析

Comparative Analysis of Continuous Cold Wave Events in Beijing-Tianjin-Hebei Region in January 2016

2016年1月京津冀地区在相隔较短的时间内连续出现2次寒潮天气,利用NCEP/NCAR再分析资料、常规观测资料和卫星云图,综合对比2次寒潮过程中的环流形势、前期回暖、冷平流、海平面气压及下沉运动等。结果表明:(1)寒潮Ⅰ主要影响京津冀北部及河北中部和南部的部分地区,以降温为主;寒潮Ⅱ的影响范围更广、强度更大,京津冀大部分地区出现明显降温和大风天气。(2)前期回暖、横槽转竖南压是2次寒潮天气的共同点,但寒潮Ⅱ的影响程度更大,主要原因为:①冷空气南下过程中有南支槽接应时,气流的经向度加大、偏北分量增强,能够快速引导冷空气主体大举向南爆发;②地面强冷高压形成较强的气压梯度和温度梯度,造成明显的梯度风;③下沉气流核所到达的高度越接近地面、持续时间越长,造成大风和降温的程度越剧烈。(3)寒潮天气过程中,气温变化若仅受单一冷平流作用的影响,最高气温和最低气温的降幅区域会比较接近;当云覆盖的影响增强时,会出现最高气温和最低气温降幅区域差异较大的情况。

It was exceptionally rare that two cold wave events occurred in Beijing-Tianjin-Hebei region during a short period in January 2016.Based on NCEP/NCAR reanalysis data,conventional observation data and satellite cloud images,the circulation situation,early warming,cold advection,sea level pressure and descending motion during two cold wave processes were comprehensively compared.The results are as follows:(1)Cold wave I mainly affected northern Beijing-Tianjin-Hebei and part of central and southern Hebei Province,and caused temperature drop.Cold wave II had a wider-impact area,and there were obvious cooling and gale in most parts of Beijing-Tianjin-Hebei.(2)Early warming and transverse trough turning to vertical were the common points of these two cold wave events.The main reason for the greater impact of cold wave II was as follows:①When the cold air was connected with the south trough in the process of southward movement,the longitude of the air flow increased and the northward component enhanced,which could quickly guide the main cold air to burst southward.②The strong cold and high pressure on the ground formed a strong pressure gradient and temperature gradient,which resulted in an obvious gradient wind.③The closer the height of the sinking air core was to the ground and the longer the duration was,the more severe the influence of cold air was.(3)In the processes of cold waves,if the temperature change was only affected by cold advection,the region of maximum and minimum temperature drop would be close.When the cloud coverage increased,the region of maximum and minimum temperature drop would be quite different.