北京一次持续性雾霾过程的阶段性特征及影响因子分析

A study of the stageful characteristics and influencing factors of a long-lasting fog/haze event in Beijing

利用北京地区高时间分辨率观测资料对2009年11月3—8日一次持续性雾霾天气过程中的气象因素和气溶胶演变特征进行了分析。结果表明,该次雾霾过程具有明显的阶段性特征,前期以霾为主,中期发展为雾霾交替,后期随着相对湿度减小再次转换为霾并最终消散。边界层逆温是低能见度过程形成的必要条件,但并不最终决定雾霾低能见度强度。相对湿度和PM_(2.5)浓度是决定能见度大小的两个关键影响因子,对能见度的影响体现出阶段性特征。大部分时段PM_(2.5)浓度是影响能见度的主要因子,当能见度小于1 km时,能见度变化更多受相对湿度影响。不同的情景计算表明,控制PM_(2.5)浓度对于改善本次过程的能见度有重要作用。

The meteorological influencing factors and aerosols characteristics of a long-lasting fog/haze event in Beijing during 3-8 November 2009 were analyzed using the high resolution observations. Significant stage characteristics are revealed during the process, in which haze dominated in the early stage, then fog and haze alternated in the middle stage, and at last haze reappears and gradually dissipates with the decreasing of relative humidity （RH） and PM2.5 concentration. The results show that it is RH and PM2.5 concentration to determine visibility in the process, but the impacts of these two also show a stage characteristics. When visibility is less than 1 km, RH is an important factor to visibility. In most of the period, PM2.5 concentration plays an important role in reducing visibility. Calculations from the three scenarios show that the control of PM2.5 concentration will be crucial role in improving visibility.