能见度与PM2.5浓度关系及其分布特征

Relationship Between Atmospheric Visibility and PM2.5 Concentrations and Distributions

利用相对湿度、能见度和PM2.5质量浓度观测数据,针对不同相对湿度下,建立了消光系数与PM2.5质量浓度之间线性关系,并分析了相关关系的全国分布特征.结果表明,我国中东部大部分地区在一定相对湿度区间内均可建立线性相关关系,而且相关性较好,相对湿度40%~90%区间内的平均相关系数高于0. 75,其中北京相关系数高达0. 9.北京、长三角和四川等地的PM2.5单位质量消光效率在同等相对湿度下明显大于其他地区.不同地区湿度对能见度影响程度不同,北京等地在相对湿度大于90%时相对湿度对能见度作用大于PM2.5,而广州在相对湿度大于80%时相对湿度的作用明显增强.利用能见度反算北京地区PM2.5浓度可知,1980~1996年,PM2.5浓度年际变化不大,受采暖方式影响冬季PM2.5浓度显著较高;1997~2009年呈现缓慢下降趋势;2010~2012年呈现上升趋势. 1980年以来,全国的PM2.5浓度整体呈上升的趋势,尤其是华北地区,PM2.5浓度始终高于全国其他地区.

Monitoring data were used to analyze the relationships among relative humidity( RH),visibility,and PM2.5 concentrations.A strong,linear relationship expression between the extinction coefficient and PM2.5 concentrations at different relative humidities is proposed. The mean correlation coefficient at RH 40%-90% was higher than 0. 75 for most of Central and Eastern China,and reached0. 9 in Beijing. Comparatively,the extinction efficiency of PM2.5 was much larger in Beijing,the Yangzi River Delta Region,and Sichuan than in other regions. However,the influence of RH on visibility varied from region to region. In Beijing,RH dominated the decrease in visibility when RH > 90%,while in Guangzhou,this was the case when RH > 80%. From 1980 to 1996,the annual variation in PM2.5 concentrations was not significant in Beijing and the PM2.5 concentrations were significantly higher than in the 2000 s because of the dominant mode of heating. From 1997 to 2009,PM2.5 concentrations in Beijing showed a slow downward trend,and from2010 to 2012,showed an upward trend. Since 1980,PM2.5 concentrations in the entire country have been rising. PM2.5 concentrations have always been higher in North China than in other parts of the country.