Aerosol measurements with a combined elasticon-elastic backscatter lidar in Beijing

摘要

In order to reach a green Olympics in 2008, an unprecedented environmental experiment jointly launched by the Beijing municipal government and the Chinese Academy of Sciences (CAS) was carried out. AIOFM (Anhui Institute of Optics and Fine Mechanics Experiment) took part in the campaign with an elasticon-elastic lidar to measure the aerosol distribution and the boundary layer in summer in Beijing. With the combining solution of the Raman lidar and the elastic lidar equation, the important optical parameters of the aerosols (extinction coefficient, backscatter coefficients thus the lidar ratio) were attained. The lidar ratio on July 22 varied from 10sr to 30sr. Since the vertical distribution of the lidar ratio demonstrate different microphysical characteristics in the lower and upper parts of the cloud, so probably the cirrus with the mean lidar ratio of 25sr at the height of 6km can be assumed. On the other hand, a well-mixed boundary layer was observed. Taking into account theeffects of the multiple scattering (5%-10%),we obtain a single-scattering optical depth of 0.15.Theboundary layer also offered the explanation of the steady ozone concentration measured by the DOAS system at the same position of the observing site.