泰安市冬季一次严重空气污染过程分析

为揭示泰安市空气污染形成原因，选取泰安市2016年12月一次严重空气污染过程，利用泰安市2016年12月地面和探空资料及NCEP/NCAR（美国国家环境预报中心/美国国家大气研究中心）提供的FNL资料，对泰安市严重污染期间大气环流形势、边界层条件、污染源及传输路径进行分析.结果表明:在泰安市霾污染期间，500 hPa大气环流形势呈"两槽一脊"的特征，850 hPa泰安市处于南支槽前，受西南暖湿气流影响，为ρ（PM_2.5）的升高提供了有利条件；泰安市近地面处于高压控制下的弱风区（平均风速约为1.2 m/s）且边界层有逆温层存在，阻碍了PM_2.5的垂直输送，造成近地面ρ（PM_2.5）急剧升高.此外，泰安市及周边地区污染严重，聚类分析结果表明此次过程本地输送占比约为34%，其余均为外来传输，即污染物主要通过外来源传输，本地污染源贡献比率较小.污染物的高、低空传输路径不一致，低空污染物主要从安徽省水平输送至泰安市，高空污染物则先由河北省、河南省向南传输至安徽省、湖北省等地，再随南风气流向北输送至泰安市.研究显示，外来污染源传输作用配合本地静稳天气形势是造成此次泰安市空气污染的主要原因. 

Analysis of a Serious Air Pollution Process in Winter in Tai'an City

In order to reveal the causes of the air pollution in Tai'an City, a serious air pollution process in December 2016 was investigated. We analyzed the atmospheric circulation pattern, boundary layer conditions, air pollutant source and transport pathway by using the ground and radiosonde data in Tai'an City and the NCEP/NCAR FNL data of meteorology in December 2016. The results indicated that governed by the atmospheric circulation pattern with 'two troughs and one ridge' at 500 hPa, Tai'an City was located in front of southern branch trough and influenced by southwest warm airflows at 850 hPa, providing favorable conditions for the increases of PM_2.5 concentrations. Tai'an City was situated in the weak wind area (average wind spend is about 1.2 m/s) under high pressure control near the ground, and a temperature inversion layer existed in the boundary layer, suppressing the vertical transport of PM_2.5 and resulting in a sharp increasing in surface concentrations of PM_2.5. In addition, cluster analysis results show that the proportion of local emission was about 34% and the rest were from the external emission in this process. So, the pollutants in Tai'an City were mainly transported from the external emission sources with less contribution rates of the local sources. It is worth noting that the two pathways of air pollutant transport in the lower and upper levels were inconsistent. Lower-level pollutants were mainly transported from Anhui Province to Tai'an City; High-level pollutants were first transported from Hebei Province, Henan Province southward to Anhui Province, Hubei Province and other regions, and then transported to Tai'an City with southern air flows. The research shows that the main causes of the air pollution in Tai'an City are the transport of pollutions from the external emission sources and the local stable weather situation.