基于卫星遥感和地面观测资料分析苏皖两省一次空气污染过程

2012年6月8~11日,江苏安徽2省发生了一次持续性的空气污染过程.利用MODIS观测的气溶胶产品和地面气象资料,结合火点监测资料和HYSPLIT后向轨迹模式,分析气溶胶光学厚度(AOD)、细粒子比例(FMF)、空气污染指数(API)的特征,探究这次空气污染的形成原因.研究表明,这次过程中苏皖2省8个代表城市的能见度大部分时间低于10km,相对湿度低于90%,API均达到或超过污染等级,AOD显著增长,且污染物以人类活动产生的细粒子为主.区域细粒子比例(RFMF)达0.79,高FMF(>0.6)出现的概率高达74.8%.另外,苏皖2省稳定的天气形势,不利于污染物扩散.6月8~11日,苏皖2省(北部地区为主)出现大量的火点,表明有秸秆焚烧现象的存在.从HYSPLIT模式的模拟结果来看,苏皖2省8个代表城市在此期间主要受到偏西方向的气流以及局地气流的影响,偏西方向的气流有利于外部秸秆焚烧的污染物经过输送影响本地区,同时局地气流不利于扩散,从而造成污染物积累,形成污染.

A continuous air pollution event in Jiangsu and Anhui provinces based on satellite remote sensing and field observations

During June 8-11 2012, a continuous air pollution event occurred in Jiangsu and Anhui provinces. By using MODIS sensor aerosol productions, meteorological data and fire-spot data as well as HYSPLIT backward trajectory mode, Aerosol Optical Depth (AOD), Fine Mode Fraction (FMF) and Air Pollution Index (API) were analyzed to reveal the possible reasons for this event. Results indicated that, the visibilities in eight cities of the two provinces were mostly less than 10 km, and the relative humidities were below 90%. The API was equal to or exceeded the pollution grade. There was a significant increasing for AOD during this event. Fine particles emitted from human activities were dominated pollutants. The Regional Fine Mode Fraction (RFMF) was up to 0.79, and the frequency for FMF higher than 0.6 was 74.8%. During the pollution course, the weather condition was steady and unfavorable for pollutants dispersing. In June 8-11, lots of fires spots appeared indicating there were biomass burning events according to the MODIS sensor. Backward trajectory analysis indicated that the air in the eight cities were mostly influenced by air masses from the west which may introduce pollutants emitted from biomass burning. Local air masses also influence the air quality in these cities which were not favourable for air dispersing. Then the pollutants will be easily accumulated to form pollution.