基于激光雷达的北京市气溶胶光学参数季节特征

利用米散射激光雷达ALS300系统在北京城区开展了为期近1年的观测,观测时间为2009年6月~2010年5月份.先将观测数据划分为春(3~5月份)、夏(6~8月份)、秋(9~11月份)、冬(12~2月份)四个季节,再对数据进行质量控制.研究了气溶胶后向散射系数、消光系数以及气溶胶光学厚度AOT和大气边界层的日均值变化特征,以及这些要素的季节和全年特征统计值.结果表明,气溶胶消光系数和后向散射系数的日平均变化形态趋于相同,数量上消光系数是后向散射系数的约10倍.它们的季节平均值廓线形态结构也并没有呈现出明显的季节性结构特征差异,2个系数最大递减均发生在1km高度范围内.在0.15~3.0km高度范围做垂直平均,夏季的后向散射系数和消光系数有最大平均值(分别为31.2Mm~(-1)×sr~(-1)和517.0Mm~(-1)),说明夏季有较强对流.冬季后向散射系数和消光系数最低.对于冬、春2个季节,700m高度是2个量大小分化的高度.700m高度以上,春季的后向散射系数和消光系数均大于冬季.AOT和大气边界层高度的日均值波动特性明显,日均值最大振幅出现在春季.月平均来说,在春季,气溶胶层高度和边界层高度最高(分别为3450m和970m),冬季最低(分别为2970m和712m).春、夏季节AOT波动变化大,而在秋季和冬季变化比较平缓.春夏秋冬4个季节的平均气溶胶光学厚度分别是0.689、0.699、0.571和0.647.

Seasonal characteristics of the aerosol optical parameters based on lidar over the Beijing Area

One year measurements of Mie scatter lidar at Beijing were performed between June 2009 and May 2010. First of all, the data were split into four seasons:Spring(March-May), Summer(June-August), Autumn(September-November), and Winter(December-February). Next, the data were quality controlled. At last, Change of daily mean values of aerosol backscattering coefficient, extinction coefficient, AOT, and atmospheric boundary layer(ABL) were analyzed. At the same time, the vertical profiles of the aerosol backscattering coefficient, extinction coefficient, their variability during each season, the annual average, and the statistics were calculated, the characteristics of the AOT and the planetary boundary layer were also presented. The analyses revealed that, the average daily characteristics of the aerosol extinction coefficient and backscattering coefficient were the same, and the extinction coefficient was about 10 times of the backscattering coefficient. The seasonal mean aerosol backscatter and the extinction profiles did not exhibit significant seasonal differences in structural characteristics. The maximum decrement of the backscatter coefficients and extinction coefficient occurs within 1km above ground. The vertically averaged(between 0.15~3.0km) backscatter and extinction coefficients had the highest averages value(31.2Mm^-1·sr^-1 and 517.0Mm^-1, respectively) in summer, which reflects the stronger convection during summer. The winter had the lowest aerosol backscatter and extinction coefficients. For winter and spring seasons, 700m was the height where these two quantities showed different trend. Above 700m, the backscattering coefficient and extinction coefficient in spring were higher than those in winter. The fluctuations of daily average AOT and ABL height were significant, and the maximum amplitudes appeared in spring. On average, the residual layer and PBL were the highest in spring(3450 m and 970 m respectively), and the lowest in winter(2970 m and 604 m respectively). In spring and summer, the fluctuation of AOT varied greatly, but the fluctuation in autumn and winter was relatively mild. The average AOT in spring, summer, autumn, and winter is 0.689, 0.699, 0.571, and 0.647 respectively.