广西PM2.5时空分布特征及污染天气类型

研究区域ρ（PM_2.5）的时空分布特征和污染天气类型的关系是开展大气污染防治和空气质量预报预警的关键支撑技术之一.基于2015—2016年广西14个城市环境空气质量日监测数据和相关气象资料，分析了2015—2016年广西空气质量概况和污染的基本特征，采用EOF（经验正交函数）分析和后向轨迹聚类分析方法表征了广西ρ（PM_2.5）时空分布模态，统计了广西两年间24次区域范围（3个及以上连片城市）大气轻度及以上污染过程，分析了不同污染过程的天气类型和空气质量变化特点.结果表明:PM_2.5是广西大气污染首要污染物，ρ（PM_2.5）年均值呈北高南低的区域特征，月际变化基本呈正V字型分布；EOF分析和后向轨迹聚类分析显示，广西ρ（PM_2.5）的时空结构主要有3种模态，其方差贡献率分别为78.9%、5.7%和3.7%，基本反映了广西ρ（PM_2.5）变化的时空模态的主要特征，桂林和玉林两年间的后向轨迹聚类很好地解释了第二和第三模态的南北浓度和东西浓度异常反相位分布特征；广西14个城市两年间PM_2.5区域性污染天气类型主要有10种，其中污染天气类型中占比较大的是弱冷高压脊型（24.4%）、均压场型（20.2%）、高压后部型（16.1%）和高压后部配合西南暖低压型（8.5%），是引发广西大范围大气污染的典型天气类型.研究显示，广西大气污染具有地域性、季节性和南北输送特征，污染过程的天气形势变化具有一定规律性. 

Spatio-Temporal Characteristics of PM2.5 and Pollution Weather Types in Guangxi

In order to provide technical support for air pollution control and air quality forecast and early warning, it was necessary to study on spatio-temporal characteristics of PM_2.5 concentration and pollution weather types in region. Based on the daily air quality monitoring data and correlative meteorological data of 14 cities in Guangxi from 2015 to 2016, the air quality overview and basic characteristics of air pollution of Guangxi from 2015 to 2016 were analyzed. Methods of empirical orthogonal function (EOF) analysis, backward trajectory clustering analysis were adopted to characterize the spatio-temporal mode of ρ(PM_2.5) of Guangxi, the weather type and the variation characteristics of air quality were analyzed in different pollution processes by using the 24 times regional pollution process (AQI>100, contiguous cities ≥ 3), which occurred during the two years. The results indicated that PM_2.5 is the primary pollutant of air pollution in Guangxi, the ρ(PM_2.5) was high in the north and low in the south, monthly variation of ρ(PM_2.5) followed a V-shaped distribution; The results of EOF and backward trajectory clustering analysis showed that, there were three main spatio-temporal modes of ρ(PM_2.5), variance contribution of the three modes were 78.9%, 5.7% and 3.7%, which reflects basically the main characteristics of the variation of ρ(PM_2.5) in Guangxi. The backward trajectory clusterings of Guilin and Yulin cities from 2015 to 2016 were well explained that North-South concentration of the second mode and East-West concentration of the third mode showed the characteristic of anti-phase distribution; There were 10 kinds of regional pollution weather types of 14 cities in Guangxi during the two years, weak cold high pressure (24.4%), uniform pressure field (20.2%), back of high pressure (16.1%) and back of high pressure combined with southwest warm low (8.5%) were typical weather types which caused air pollution in large range. Research shows that air pollution in Guangxi has got the feature of regional, seasonal and south-north transport of ρ(PM_2.5), there were certain regularity in the weather situation of pollution process.