Abstract:

During the summer of 2022, the Yangtze River Basin in China is severely affected by high temperatures and drought, leading to significant variations in pollutants including ozone (O₃). Surface air quality, hourly meteorological monitoring data, and meteorological reanalysis data were used to examine the effects of high temperatures and droughts on pollutants. These data were analyzed to understand the characteristics of high temperatures and drought and their impact on O₃ and fine particulate matter (PM_2.5) concentrations. The results showed that extremely high temperatures and drought events occurred in the Yangtze River Basin of China during the summer of 2022, which is characterized by a long duration and widespread impact caused by the plateau warm high pressure, westward extension, and northward uplift of the Western Pacific Subtropical High. The Sichuan Basin and Yangtze River Delta region had higher surface temperatures, lower relative humidity, and precipitation, which had an impact on the concentrations of O₃ and PM_2.5 near the surface. The Sichuan Basin is particularly affected by high temperatures and droughts in July and August. The abnormally high temperature and drought enhanced atmospheric photochemical reactivity, contributing to the generation of ozone and secondary aerosols. The wet removal effect of precipitation on pollutants was significantly weakened, leading to a significant increase in the O₃ concentration and the number of days exceeding the standard in the Sichuan Basin. The concentration of PM_2.5, increased in some cities, even causing a compounded heat wave and ozone pollution event that lasted more than ten days. The most significant impact on O₃ pollution occurred in the Chengdu Plain, followed by urban agglomeration in southern Sichuan, where the number of days with O₃ exceedance was over 20 days and 17 days. The number of high-temperature days and O₃ exceedance days increased by approximately 250% and 120%, respectively, in the Chengdu Plain compared with 2021. In addition to the influence of high-temperature heat waves, topographical obstruction of the plateau and vertical wind transport are important factors that affect O₃ pollution in the Sichuan Basin.

Key words: high temperature and drought, western pacific subtropical high, ozone pollution, compound event, the Sichuan Basin

摘要：

2022年夏季高温干旱严重影响中国长江流域，臭氧（O₃）等污染物也出现明显异常，为研究高温干旱对污染物的影响，利用2015-2022年夏季逐小时地面空气质量和气象监测数据以及气象再分析资料，分析了夏季高温干旱特征以及对O₃和细颗粒物（PM_2.5）浓度的影响。结果表明：2022年夏季受高原暖高压和西太平洋副热带高压西伸北抬的影响，中国长江流域出现极端高温干旱天气事件，持续时间长，影响范围广，其中四川盆地和长三角地区地面温度明显偏高，相对湿度和降水量偏低，对近地面O₃和PM_2.5浓度造成了一定的影响。7-8月高温干旱对四川盆地产生的影响尤其严重。异常的高温干旱增强了大气光化学反应能力，对O₃和二次气溶胶生成有贡献，且降水对污染物的湿清除作用大大减弱，导致四川盆地O₃浓度和超标天数明显增加，PM_2.5浓度也有所升高，甚至造成持续十多天的高温热浪和O₃污染复合事件，其中对成都平原O₃污染的影响最为显著，其次为川南城市群。成都平原和川南城市群O₃超标天数分别为22 d和17 d；成都平原高温日数和O₃超标天数分别比2021年增加了约250%和120%。除高温热浪的影响外，高原地形阻挡以及风的垂直输送也是四川盆地O₃污染形成的重要原因之一。

关键词: 高温干旱, 西太平洋副热带高压, 臭氧污染, 复合事件, 四川盆地