新冠肺炎疫情期间天津市重污染天气的边界层特征

Boundary layer characteristics of heavy pollution process in Tianjin during the epidemic period of COVID-19

为探讨新冠肺炎疫情期间天津市重污染天气成因,利用环境监测、气象常规观测及255 m气象塔梯度观测,结合WRF-Chem模式研究了天津市2020年2月9—13日新冠肺炎疫情期间重污染过程来源及边界层特征。结果表明:水平和垂直扩散条件变差、地面弱气压场和暖湿明显为此次重污染天气的主要特征;重污染天气过程外来源的区域输送率达54.6%;稳定类层结(E类和F类)占比高达67.5%,较为稳定的大气造成大气扩散条件变差,是污染发生的重要气象条件;污染过程逆温率达50.0%,垂直温差、逆温厚度、逆温强度与PM_(2.5)浓度相关性分别为0.99、0.90和0.56,逆温层的存在是污染过程维持的主要因素。

In order to investigate the causes of heavy pollution in Tianjin during the epidemic period of COVID-19 in 2020,the environmental monitoring,routine meteorological observation and 255 m meteorological tower gradient observation,together with WRF-Chem model simulation were used to discuss the sources and boundary layer characteristics of heavy pollution process during February 9-13th,2020 in Tianjin.The results showed that the deterioration of horizontal and vertical diffusion conditions,weak air pressure field and warm and humid atmosphere on the ground were the main weather characteristics of this heavy pollution case.The regional transportation rate of external sources in the process of heavy pollution was 54.6%.The stable stratification(E and F)accounted for 67.5%,and the relatively stable atmosphere decreased the atmospheric diffusion condition,which was an important meteorological condition for the occurrence of this pollution.The inversion rate of the pollution process reached 50.0%,and the correlations between the vertical temperature difference,inversion thickness,inversion intensity and PM_(2.5) concentration were 0.99,0.90 and 0.56,respectively.The existence of inversion layer was the main factor to maintain the pollution process.