福建省PM_(2.5)-O_(3)双高特征与天气形势影响分析

Analysis of the Characteristics of PM_(2.5)-O_(3) Compound Pollution and the Impact of Synoptic Weather Patterns in Fujian Province

为理清福建省天气形势对PM_(2.5)与O_(3)演变的影响,识别二者的不同趋势与特点,揭示双高过程的气象场特征,利用2015-2021年PM_(2.5)与O_(3)连续观测资料,采用统计合成、天气学诊断等方法,探究PM_(2.5)与O_(3)变化趋势、污染状况及其与主导天气形势的关系,阐明气象因素对PM_(2.5)与O_(3)(简称“PM_(2.5)-O_(3)”)双高过程的协同作用。结果表明:2015-2021年福建省PM_(2.5)质量浓度年均值呈明显下降趋势,超标天数从5.6 d(2015年)下降到0.3 d(2021年)。O_(3)日最大8 h平均(简写为O_(3)-8h)质量浓度的年均值呈先上升后略下降的趋势,2018年O_(3)超标天数为2016年的8倍以上。天气形势对PM_(2.5)与O_(3)的影响存在一致性特征,也存在差异性,2015-2021年PM_(2.5)质量浓度在不利天气形势下从34.9μg∙m^(-3)降至24.8μg∙m^(-3),在有利的天气形势下从25.2μg∙m^(-3)降至17.5μg∙m^(-3),且不利天气形势下与有利天气形势下的质量浓度差在缩小。O_(3)-8h质量浓度在有利的天气形势下呈现上升趋势,在中性-拉尼娜气候背景加不利天气形势下却呈略降趋势,可见近年来针对O_(3)的管控措施是有一定效果的。福建省PM_(2.5)-O_(3)双高现象白天发生频率远高于夜间,协同控制最需要关注的是光化学型PM_(2.5)-O_(3)双高现象(08:00-20:00的PM_(2.5)-O_(3)双高现象),主要天气形势有两种,即2-5月锋前暖区下的静稳天气以及7-9月台风外围影响下的静稳天气;沿海代表性城市莆田市非光化学型PM_(2.5)-O_(3)双高现象(21:00至翌日07:00的PM_(2.5)-O_(3)双高现象)占比14.1%,说明加强上游区域的联防联控也是PM_(2.5)-O_(3)协同控制的关键因素之一。研究显示,近年来PM_(2.5)和O_(3)-8h浓度演变与天气形势变化有密切关系。期望研究成果能为低污染排放区域PM_(2.5)与O_(3)协同控制、污染防控效果评估奠定基础。

In order to explore the impact of weather conditions in Fujian Province on the changes of fine particulate matter(PM_(2.5))and Ozone(O_(3)),including their characteristics and differences,we have investigated observational PM_(2.5) and O_(3) during 2015 and 2021 based on the methods of statistical synthesis and synoptic diagnosis.Typical PM_(2.5)-O_(3) compound pollution(PM_(2.5)-O_(3))episodes were selected to reveal the meteorological mechanism of compound pollution.The number of PM_(2.5) polluted days decreased from 5.6 days in 2015 to 0.3 days in 2021.The maximum daily 8 h average c(O_(3)-8h)concentrations increased rapidly and then decreased slightly,and the number of annual polluted days in 2018 was more than 8 times that of 2016.The impact of synoptic weather patterns on PM_(2.5) and O_(3) had consistent characteristics and also differences.The PM_(2.5) concentrations decreased from 34.9μg∙m^(-3) to 24.8μg∙m^(-3) and from 25.2μg∙m^(-3) to 17.5μg∙m^(-3) under unfavorable and favorable synoptic weather patterns,respectively.It was noted that O_(3)-8h concentrations showed an upward trend under favorable synoptic weather patterns,and decreased slightly in neutral La Nina years and unfavorable synoptic weather patterns,which proved the effectiveness of the O_(3) pollution control in recent years.The frequency of PM_(2.5)-O_(3) compound pollution in Fujian province is much higher during the day than that at night.According to observations,photochemical formation contributed most to PM_(2.5)-O_(3) pollution,which tended to occur between 08:00 to 20:00.Photochemical reaction could be promoted when the study area was in the warm frontal area or peripheral circulation of typhoon,both of which led to more stagnant conditions.Moreover,pollution episodes could occur at night(21:00–07:00 in the next morning)without photochemical reaction in coastal city Putian,which contributed to 14.1%of all pollution episodes.Thus,it is necessary to strengthen the regional joint prevention and control mechanism.Research has shown that the evolution of PM_(2.5) and O_(3)-8h concentrations in recent years is closely related to changes in synoptic weather patterns.The research results will assist in the regional prevention and control of PM_(2.5) and O_(3),,and the evaluation of pollution prevention and control effects in low pollution emission areas.