京津冀及周边地区夏季和初秋气象条件对PM_(2.5)和O_(3)双高影响

Effects of Meteorological Conditions in Summer and Early Autumn on PM_(2.5) and O_(3)Pollution in Beijing-Tianjin-Hebei and Surrounding Areas

为了解2021年京津冀及周边地区夏季和初秋的PM_(2.5)和O_(3)的双高特征及气象影响,对京津冀及周边地区PM_(2.5)和O_(3)浓度的时空分布特征以及气象条件、副高指数和天气形势进行了分析.结果表明,2021年6~9月PM_(2.5)浓度和DPO_(3)[O_(3)日最大8 h均值与06:00 O_(3)浓度的差值]与2020年和2022年同期相比都有所降低,浓度高值主要集中在6月;PM_(2.5)浓度和DPO_(3)整体呈现从中部向南北逐渐下降的特征,并具有同步的时空变化特征.PM_(2.5)浓度小时均值呈双峰分布,在07:00~10:00和22:00~24:00达到峰值;O_(3)浓度小时值呈相反的变化趋势,在14:00~16:00达到峰值.高PM_(2.5)浓度和DPO_(3)时近地面气象要素特征表现为气温在24.0~28.0℃,相对湿度在58.4%~76.3%,风速在1.5~3 m·s^(-1).副高指数与DPO_(3)存在滞后相关,当副高离京津冀及周边地区越远且强度越强时,DPO_(3)越高.研究区域PM_(2.5)和O_(3)浓度双高的主要天气形势为近地面低压前部、高压型和锋前型,高空受高压脊控制且副高脊线稳定在21°~28°N.

PM_(2.5) pollution remains prominent in autumn,whereas O_(3)pollution gradually manifests in summer.To understand the dual high characteristics and meteorological effects of PM_(2.5) and O_(3)in the summer and early autumn of 2021 in the Beijing-Tianjin-Hebei and surrounding areas,the spatiotemporal distribution characteristics of PM_(2.5) and O_(3)concentrations,as well as meteorological conditions,subtropical high index,and weather situation in the Beijing-Tianjin-Hebei and surrounding areas were analyzed.The results showed that PM_(2.5) concentration and DPO_(3)(O_(3)daily maximum 8h mean minus O_(3)concentration at 06:00)from June to September 2021 decreased compared with those in the same period in 2020 and 2022,and high concentrations were mainly occurring in June.The overall PM_(2.5) concentration and DPO_(3)showed a gradual decrease from the middle to the north and south,with synchronous spatiotemporal changes.The hourly value of PM_(2.5) concentration presented a multimodal distribution,reaching the peak at 07:00-10:00 and 22:00-24:00.O_(3)concentration showed an opposite trend of change with PM_(2.5) concentration,reaching their peak from 14:00-16:00.When DPO_(3)and the concentration of PM_(2.5) were high,the characteristics of near-surface meteorological elements were characterized by temperatures ranging from 24.0-28.0℃,relative humidity concentrated at 58.4%-76.3%,and wind speeds ranging from 1.5-3 m·s^(-1).There was a high lag correlation between the subtropical high index and DPO_(3).When the subtropical high was farther and stronger from the BeijingTianjin-Hebei and surrounding areas,DPO_(3)was higher.The major weather patterns with both high PM_(2.5) and O_(3)concentrations in the study area were near surface low-pressure front,high-pressure type,and frontal type.The high altitude was controlled by high-pressure ridges,and the subtropical high ridge line was stable between 21°-28°N.