河南3次重污染天气过程的气象条件诊断及传输影响分析

Meteorological Condition Diagnosis and Transmission Impact Analysis of Three Heavy Pollution Processes in Henan Province

利用空气质量监测数据、气象常规观测资料、L波段雷达探空资料、EC-Intrim再分析资料和NCEP全球资料同化系统提供的再分析资料,以及HYSPLIT模式模拟结果,分析了2016年12月至2017年1月间发生在河南的3次重污染天气过程的影响范围、气象条件和传输影响等。结果表明,3次过程河南地区均呈现出500 hPa等高线平直、9251000 hPa风垂直切变小和海平面气压场均压等特征。在近地面,3次过程在污染开始和加强时段均有小风和低湿特征,过程临近结束时有大风或增湿出现。前两次污染过程为干霾过程,均因加强的偏西风而结束,但是在结束阶段,相较于第1次过程的西南风,第2次过程的西北风能更快速有效地清除污染物;第3次过程为湿霾(雾、霾混合)过程,因偏东风而结束,但由于偏东风风力较小,对污染物彻底清除能力有限,过程结束后很快出现反复。郑州近地面存在明显逆温和“上干下湿”的层结特征,这种“干暖盖”严重阻碍着空气的对流运动,使近地层的污染物垂直扩散能力变弱,从而导致污染加重。HYSPLIT后向轨迹传输影响显示,第1次过程主要以省外西北路输送为主,后两次过程主要以本省和本地累积为主。

Based on the air quality data,conventional meteorological observations,L-band sounding data,EC-intrim reanalysis data,NCEP Global Data Assimilation System(GDAS)reanalysis data,and HYSPLIT model simulation,three heavy air pollution events from December 2016 to January 2017 are contrastively analyzed in terms of impact scope,meteorological conditions and transmission impacts.The results indicates that all the three heavy pollution events took on the features of flat isohypse at 500 hPa,small vertical wind shear for 925—1000 hPa and uniform pressure field.In the near surface,light winds and low humidity appeared in the onset and strengthening stages of the pollution processes,and strong winds or wetting occurred near the end.The first two events were dry hazes,terminated due to the strengthening westerly wind.At the end of stage,compared with the southwest wind in the first process,the northwest wind in the second process worked more quickly and efficiently.The third pollution event was wet haze mixed with fog.It was terminated by persistent easterly wind,but the wind was too weak to thoroughly clean the pollutants,thus easily resulting in a return of air pollution.In the near surface of Zhengzhou,the stratification features of obvious temperature inversion and“wetter in low level compared to upper air”(i.e.,warm dry lid)hindered the air convection,weakening vertical diffusion of pollutants and aggravating the pollution.In terms of transmission impact of HYSPLIT backward trajectory,the first event was mainly the transmission by northwest paths from other provinces,and the latter two were locally accumulated.