2022年广东省冬季一次臭氧污染过程的气象成因及潜在源区分析

Meteorological Formation Mechanisms and Potential Sources of an Ozone Pollution Process in Winter of 2022 in Guangdong Province

气象条件是造成臭氧季节变化的重要原因,为了解广东省冬季臭氧污染的气象成因,使用空气质量和气象要素的地面、垂直探测资料和再分析资料,选取了2022年1月3~6日广东省臭氧中度污染过程与2015~2021年秋季(高污染季)进行对比分析.结果表明:(1)污染过程期间超标城市总数为8个,其中1月4日肇庆达中度污染(219μg·m^(-3));广东省ρ(O_(3)-8h)平均值为123μg·m^(-3),较历史秋季平均浓度偏高了21%,但臭氧污染影响范围小于历史秋季污染过程.(2)风速偏小、日照时数偏长和局地环流影响下的气流回流效应是此次臭氧污染过程最主要的地面气象条件,气温偏低可能是这次污染过程影响范围偏小的重要原因.(3)垂直探测表明,夜间至早晨的贴地逆温,配合下沉气流偏强、风速偏小,使得上午时段NO_(2)浓度维持较高水平,进一步促使臭氧浓度增量比非污染时段偏高34.2μg·m^(-3),残留层臭氧下传加剧1月4日臭氧污染.(4)气流轨迹分析显示臭氧存在水平输送和高空地面混合,近地面不同高度潜在源区主要集中在广东省内,此次污染过程受广东省本地排放影响较大.

Meteorological conditions play an important role in seasonal ozone variations.In order to understand the meteorological formation mechanisms of ozone pollution in Guangdong Province in winter,the moderate ozone pollution process in Guangdong Province from January 3-6,2022 was selected for comparison with that in autumn(high pollution season)of 2015 to 2021.The research was based on ground and vertical sounding data and reanalysis data of air quality and meteorological elements.Eight cities exceeded the standard during the pollution process,among which Zhaoqing showed moderate pollution(219μg·m^(-3))on January 4th.The average O_(3)-8h concentration in Guangdong Province was 123μg·m^(-3),which was 21%higher than that in historical autumn.However,its scope of pollution was less than the historical pollution processes in autumn.Lower wind speed,longer sunshine hours,and airflow reflux effect under local circulation were the most important ground-level meteorological conditions for the ozone pollution process,whereas lower temperature might be an important reason for its small scope of pollution.Vertical detection analysis showed that the combined effect of low-level temperature inversion layer,stronger downdraft,and lower wind speed kept the NO_(2) concentrations at a high level,and further induced a higher increment of ozone concentration in the morning(34.2μg·m^(-3) higher than that in the non-pollution period).The downward transport of ozone in the residual layer aggravated the ozone pollution on January 4th.The accumulation of ozone and its precursors was an important factor of the aggravation of ozone pollution the following day.Airflow trajectory analysis revealed that the ground-level ozone was affected by horizontal transport and vertical mixing of pollutants.Potential sources at 10 m were mainly distributed in the coastal areas from Fujian to Guangdong,and the scope of potential sources was concentrated in Guangdong as the height increased.Airflow backward trajectories at different heights during the ozone process passed over the areas of potential sources in Guangdong,which indicated that the local emissions in Guangdong had a greater impact on the ozone pollution process.