南宁地区一次典型灰霾过程气溶胶光学特性的地基观测

Aerosol Optical Properties Derived from Ground-based Measurement during a Haze Pollution Episode in Nanning

基于太阳辐射光度计和微脉冲激光雷达,对南宁地区2014年10月发生的1次典型灰霾天气进行了连续观测.气溶胶光学厚度(AOD)在灰霾污染事件期间(1.23±0.19,440nm波段)显著上升,是消散期(0.57±0.14)及发生发展期(0.98±0.25)的2.2倍和1.3倍.灰霾期间同步上升的ngstrm指数表明细颗粒物的消光贡献上升.灰霾天气期间气溶胶粒径谱均呈现双峰分布,严重灰霾期间的细模态体积浓度峰值(0.23μm3/μm2)高于发生发展阶段(0.15μm3/μm2)和消散阶段(0.08μm3/μm2),表明灰霾气溶胶中细颗粒物占主导.激光雷达反演得到灰霾发生发展期、严重期、消散期的日平均边界层高度分别为430±105,375±97m和710±240m,对应近地消光系数分别为0.14,0.27km-1和0.05km-1.严重灰霾期间的最大消光系数出现在凌晨(0.36km-1),对应较差的污染物扩散(气象)条件以及近地面颗粒物的累积.

Based on sun-photometer and micro-pulse lidar （MPL）, aerosol optical properties were studied during a haze pollution episode over Nanning in October, 2014. Aerosol optical depth （AOD） was found to increase （1.23±0. 19 at 440 nm） significantly during the episode, which was 2. 2 and 1.3 times as high as clean （0. 57± 0. 14） and developing （0. 98±0. 25） period, respectively. Angstrom exponent was inversed to increase along with AOD during haze, which demonstrated the ascending optical extinction contribution from fine aerosol. It was revealed that size distribution show bimodal pattern. The higher volume concentration of haze condition （23μm/μm2 ） than clean and developifig period outlined the domination of fine mode during pollution. From MPL, the planet boundary layer height was measured to be 430±105 m, 375±97 m and 710±245 m. The corresponding near surface extinction ratio was inversed as 0. 14 km-1 , 0. 27 km-1 and 0. 05 km-2. During the severe haze pollution episode, the extreme optical extinction ratio （0. 36 km-1） was found at midnight near surface, which should be a result of unfavorable dispersion condition and particle accumulation. In clean day, the maximum extinction ratio was shown after noon at middle PBL, which may be related with mixing effect and secondary aerosol formation.