The atmospheric extinction coefficient can characterize the degree of contamination,it is closely related to relative humidity.This paper statistical analyzed the correlation of atmospheric extinction coefficient,relative humidity and PM2.5 mass concentration using the data from June 2013 to May 2014.On the basis of this,the temporal distribution characteristics of air pollution in Chengdu and the influence of relative humidity and PM2.5 concentration on the moisture absorption and growth characteristics of fine particles were analyzed.The results showed:(1) The extinction coefficient of Chengdu has obvious seasonal characteristics,and the value of extinction coefficient is in the order of winter ＞ autumn ＞ summer ＞ spring.The diurnal variation of extinction coefficient shows different trends in different seasons.(2) When the relative humidity is less than 80％,the PM2.5 concentration is positively correlated with the extinction coefficient,and the pollutant concentration can be directly used to represent the severity of the pollution.(3) The average unit mass extinction coefficient shows randomness with the change of relative humidity,but generally shows positive correlation.On average,the average unit mass extinction coefficient increases by 0.013％ for each additional unit of relative humidity.(4) Because the relative humidity of Chengdu has a great influence on the extinction coefficient,it is more scientific to use the air quality index to evaluate the pollution degree than using the visibility assessment.%大气消光系数可以表征污染程度的大小,其本身与相对湿度密切相关.对2013年6月～ 2014年5月的逐小时地面观测的大气消光系数、相对湿度和PM2.5质量浓度数据进行统计与相关分析,以了解成都市大气污染的时间分布特征以及相对湿度和PM2.5质量浓度对其影响,在此基础上分析细颗粒物的吸湿增长特性.结果表明:(1)成都市消光系数具有明显的季节特征,消光系数大小依次为冬季＞秋季＞夏季＞春季.消光系数日变化在不同季节表现出不同的变化趋势.(2)当相对湿度小于80％时,PM2.5浓度与消光系数显著正相关,可直接利用污染物浓度代表污染的严重程度.(3)平均单位质量消光系数随相对湿度的变化表现出随机性,但整体呈现正相关.就平均而言,相对湿度每增加一个单位,平均单位质量消光系数增加0.013％.(4)由于成都市相对湿度对消光系数影响较大,因此在评定污染程度时用空气质量指数进行评定比用能见度评定更具科学性.
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