安徽省持续性区域霾污染的时空分布特征

根据天气和气候特征,将安徽省分为沿淮淮北、江淮之间和沿江江南3个子区,并定义了持续性区域性霾过程.基于气象、环保及遥感资料,分析了安徽省持续性区域性霾过程及相应的气溶胶污染的时空分布特征.结果表明,江淮之间和沿江江南区域性霾日数自1980年开始总体呈增多趋势,沿淮淮北2000年开始增加趋势明显;1980年以来,城市持续性霾过程呈增多趋势,但城市之间差异较大;2000年之后持续性区域性霾过程明显增多,最长过程可达10d以上.62%以上的持续性区域性霾过程出现在冬季;江淮之间次数最多,沿江江南次数最少.区域性霾天气常对应着大范围的高湿、小风情况,并伴随着高浓度气溶胶污染,其光学厚度大于0.9,约是晴空天的2.3倍,气溶胶主要集中在400m以下,如近地面区域性霾天的消光系数是普通霾天的2~2.5倍,晴空天的3~5倍;地面PM_2.5污染而言,区域性霾天至少有一个或以上的城市AQI会达到轻度以上污染等级的概率超过了75%.

The trend of persistent regional haze in Anhui Province and corresponding characteristics of aerosol pollution

According to weather and climate characteristics, Anhui was divided into three sub-regions. Then, a regional haze day was defined as "more than one third of observational sites in a region reached standards of haze day", and when a region experienced a consecutive 4d or more regional haze days it was defined as a persistent regional haze event. Using data of meteorology, environment, and remote sensing from satellite and ground-based lidar, the spatial-temporal distributions of persistent reginal haze in Anhui province and corresponding aerosol pollution were investigated. The annual regional haze days showed increasing trends since 1980 in the two sub-regions to the south of Huai River, while it showed evident increasing trend after 2000 in region along and to the north of Huai River. Since 1980, persistent haze events in cities in Anhui province showed increasing trend, but with large differences among cities in the same sub-region. Since year of 2000, the occurrence of persistent regional haze events increased obviously, even emerging consecutive 7~10d or more than 10d regional haze events. Persistent regional haze occurred most in the region between Yangtze and Huaihe Rivers, and least in the region along and to the south of Yangtze River, with more than 62% occurred in winter. Regional haze usually corresponded to regional high humidity and small wind speed in meteorological conditions, accompanied by high concentration of aerosol pollution, e.g. regional AOD over 0.9, which was around 2.3 times of the clear day. Aerosol was concentrated below the lowest 400m on regional haze days, e.g. the near surface extinction coefficient was around 2 to 2.5 times of the regular haze days and 3 to 5 times of the clear days; as for PM_2.5 pollution at ground level, on a regional haze day, the probability of at least one city having AQI over 100 (lower AQI limit of light pollution) exceeded 75%.