杭州市区大气气溶胶吸收系数观测研究

An observational study on aerosol absorption coefficient in urban site of Hangzhou

利用2011年6-8月和2011年12月-2012年2月杭州国家基准气候站内黑碳及气象观测资料,分析了杭州市区气溶胶吸收系数的变化特征.结果表明,杭州市区气溶胶吸收系数冬季[(42.3±17.7)Mm-1]要高于夏季[(35.8±10.5)Mm-1],且冬季气溶胶吸收系数变化较为剧烈.在边界层变化以及人类活动的共同影响下,气溶胶吸收系数呈现明显的双峰型日变化特征,峰值出现在07:00-09:00,谷值出现在14:00,次峰值出现在19:00-20:00.通过拟合小时平均值最大出现频率得出该地区气溶胶吸收系数本底值为24.7Mm-1.霾时气溶胶吸收系数要高于非霾时,随着霾污染的加重,气溶胶吸收系数呈现阶梯上升趋势.霾期间气溶胶吸收系数的增加是造成能见度下降的重要原因之一.

The variations of the aerosol absorption coefficient in the urban area of Hangzhou city for the period from April to June, 2011 and from December, 2011 to February 2012, were studied using black carbon and conventional meteorological date at national basic meteorological stations. The results showed that the absorption coefficient in winter [（42.3±17.7）Mm^-1] was higher than that in summer [（35.8±10.5）Mm^-1] and the aerosol absorption coefficient changed violently in winter. The diurnal variation of the aerosol absorption coefficient presented a double-peak on effects of boundary layer evolution and human activities, the peak value appeared at 07：00-09：00, the valley value appeared at 14：00, the second peak value appeared at 19：00-20：00. The most representative aerosol absorption coefficient was 24.7Mmt, which was calculated by fitting hourly frequency distribution. Aerosol absorption coefficient in haze was higher than that in no-haze. The increase in haze pollution led to step up trend of aerosol absorption coefficient, which may be one of the important reasons for visibility degradation.