福州市PM_(2.5)污染过程中大气边界层和区域传输研究

以福建省会福州市2013年1月空气质量变化为对象,分析大气边界层变化和周边区域污染物传输对福州市大气颗粒物PM2.5的影响.利用福州市2013年1月逐日地面和探空观测资料以及NCEP提供的2013年1月FNL分析资料,通过大气边界层要素与PM2.5浓度之间的相关性,对PM2.5污染过程的大气边界层特征进行分析;同时采用HYSPLIT后向轨迹模拟及区域风场相关矢分析对影响福州雾霾的污染物区域传输路径进行探讨.结果表明:地面气温与PM2.5浓度呈正相关,地面风速与PM2.5浓度呈负相关,近地面边界层条件有利于霾颗粒物的形成和累积.但不同于我国东部主要污染源区霾污染过程中存在大气边界层逆温,福州PM2.5污染过程中并未出现大气边界层逆温结构,这一边界层结构的垂直混合可有利于区域传输的污染物从上层大气到达近地面从而加重福州霾污染,福州是华东地区一个PM2.5污染物的主要接受区,PM2.5污染物主要以外源输送为主.2013年1月份福州市清洁日近地面风向为海洋吹向大陆的东南风,霾污染日则为大陆吹向海洋的偏北风,PM2.5污染物主要从长三角地区、苏北以及安徽河南一带通过东北和西北方向的传输路径影响福州的空气质量.

Analysis on atmospheric boundary layer and regional transport during PM2.5 Pollution episodes in Fuzhou

In this study focusing on the air quality changes in January 2013, Fuzhou, the capital city of Fujian Province, we investigated the impacts of changes in atmospheric boundary layer and regional air pollutant transport on the atmospheric particulate matter PM2.5 in Fuzhou. By using the ground and radiosonde data operationally observed in Fuzhou and NCEP FNL analysis data of January 2013, the atmospheric boundary variations were characterized by the correlation analysis between atmospheric boundary layer elements and PM2.5 concentrations. By employing the HYSPLIT backward trajectory model and the correlation vector analysis, the regional pollutant transport to Fuzhou in January 2013 was explored. The results indicated that surface air temperature were positively correlated with the PM2.5 concentrations, while near-surface wind speeds were negatively correlated with PM2.5 concentrations, reflecting that favorable boundary layer conditions are conducive to the local formation and accumulation of haze pollutants. However, none of temperature inversion structures existed in the boundary layer during the high PM2.5 pollution in Fuzhou, differently from the typical temperature inversion layer for haze occurrences over the pollutant source regions in Eastern China. The non-inversion in vertical temperature structures in Fuzhou implied that Fuzhou haze events with the vertical mixing of air pollutants from upper layer to surface layer could be greatly contributed from the regional air pollutant transport, and Fuzhou was regarded as a receptor region of PM2.5 pollutants imported from its surrounding source regions. The HYSPLIT modeling and the correlation vector analysis confirmed that the clean days with low PM2.5 in January 2013 were accompanied with southeast winds from ocean to land; the PM2.5 levels for the haze pollution were enhanced by the transport in the northerly winds from the pollutant source region over the Yangtze River Delta region, northern Jiangsu and Anhui, Henan area. The regional transport pathways and source regions of PM2.5 for Fuzhou in January 2013 were identified.