基于风廓线雷达的成都地区一次持续性臭氧污染过程分析

Analysis of a persistent ozone pollution process in Chengdu based on wind profile radar

利用成都地区空气质量数据、地面气象观测和成都天府风廓线雷达资料,对2023年7月成都地区一次持续性臭氧污染天气过程的大气边界层特征进行了研究.结果表明:本次污染过程,成都地区前期主要受青藏高压外围西北气流影响,后期转为大陆高压和副热带高压系统共同影响;高温低湿强辐射无雨的地面气象条件有利于臭氧生成;边界层水平风速普遍小于4 m·s^(-1),垂直上升和下沉运动弱;臭氧浓度与边界层通风系数呈负相关,相关系数为-0.63,非污染日的平均通风系数(8501 m^(2)·s^(-1))约为污染日(3648 m^(2)·s^(-1))的2.3倍,通风系数对污染态势的变化具有指示意义;回流指数与臭氧污染过程的发生存在反向关系,当边界层内整层或部分高度层回流指数小于0.4时,臭氧污染发生的可能性较大.

Based on the air quality data,ground meteorological observations and wind profile radar data,the atmospheric boundary layer characteristics of a persistent ozone pollution process in Chengdu during July 2023 were analyzed.The results showed that in the early stage of this pollution process,Chengdu was mainly affected by the north-west airflow in the periphery of the Qinghai-Tibetan high pressure,and later became influenced by both the Qinghai-Tibet high pressure and subtropical high pressure system.The ground meteorological conditions of high temperature,low humidity,strong radiation,and no precipitation were conducive to ozone generation.Horizontal wind speeds in the boundary layer were generally less than 4 m·s^(-1),and vertical upward and downward movements were weak.There was a negative correlation between ozone concentration and boundary layer ventilation index,with a correlation coefficient of-0.63.The average boundary ventilation index of clean days(8501 m^(2)·s^(-1))was approximately 2.3 times of that on polluted days(3648 m^(2)·s^(-1)),indicated that the ventilation index is useful to characterize air pollution trends.There was an inverse relationship between the recirculation factor and ozone concentration.The occurrence of ozone pollution was higher when the recirculation factor of the whole or partial of the boundary layer was less than 0.4.