北京上空气溶胶浓度垂直廓线特征

利用2008—2010年北京地区3.5 km高空内飞机探测的气溶胶(粒径范围为0.10～3.00 μm)数据,分析了该地区气溶胶的时空分布特征. 结果表明:①气溶胶浓度(以数浓度计,下同)均随高度增加而减小,在1.5 km以上高空的气溶胶浓度垂直梯度变化明显低于1.5 km以下的垂直梯度变化. 4—11月气溶胶浓度季节变化表现为夏季最高、秋季次之、春季最低. ②气溶胶浓度廓线逐时(09:00—19:00)变化较清晰地反映出其受大气边界层演变的影响. 在0～1.5 km高空,白天气溶胶浓度高值出现在09:00—11:00,低值出现在13:00—14:00；而在1.5～3.5 km高空的气溶胶浓度时段分布与其相反. ③人为活动是影响气溶胶浓度区域水平分布的重要因子. ④将气溶胶浓度廓线垂直分布分为a、b、c 3类. 类型a的近地面气溶胶浓度(0～4 000 cm-3)低,垂直方向上变化很小；类型b的近地面气溶胶浓度(4 000～9 000 cm-3)较高,垂直递减明显；类型c的近地面气溶胶浓度特别高,量级达到104 cm-3,并在大气边界层顶(约1.5 km)附近迅速递减. 北京地区气溶胶浓度廓线以类型b居多. 

Vertical Profiles of Aerosol Concentration in Beijing

Based on aircraft measurements of aerosols with diameter 0.10-3.00 μm over the Beijing region from 2008 to 2010, the temporal and spatial distributions of aerosols over this region were analyzed. The major results include:1) The number concentration of aerosols decreased with the increase of altitude, especially within an altitude of 1.5 km. During the observed period (April to November), the number concentration of aerosols was highest in summer, followed by autumn, and lowest in spring. 2) The vertical distribution of aerosols was influenced by the evolution of the planetary boundary layer (PBL). The number concentration of aerosols in the altitude of 0-1.5 km was higher in the morning (09:00-11:00) and lower in the afternoon (13:00-14:00). The hourly change of aerosol concentrations at 1.5-3.5 km was contrary to that below 1.5 km. 3) Human activity is an important factor influencing the regional horizontal distribution of aerosol concentrations. 4) Vertical distribution of aerosol concentrations profiles could be divided into three types a, b and c. Under the type a condition, the vertical distributions of aerosol particles were flat with a low surface aerosol concentration (0-4000 cm-3). Under the type b condition, the aerosol concentration gradually decreased with altitude, with modest surface concentrations (4000-9000 cm-3). Under the type c condition, surface aerosol concentrations were very high (with a magnitude of 104 cm-3), and there was a sharp transition of aerosol concentrations at the top of the PBL (1.5 km). The major type of aerosol vertical distribution in Beijing area was type b.