LR measurement of cirrus clouds based on rotational raman-MIE scattering lidar

Cirrus clouds have an important impact on the radiation budget of the earth-atmosphere system as well as weather and climate. Extinction-to- backscatter ratio (Lidar ratios, LR) is an important parameter of studying cirrus clouds' optical properties. A new method bases on using rotational Raman and Mie scattering Lidar to reverse extinction-to-backscatter ratio of cirrus clouds is introduced in this paper. Rotational Raman scattering echo is only associated with backscatter coefficient of gas molecules at certain rotational quantum number rather than backscatter coefficient of atmospheric aerosols. According to the characteristics above, the backscatter coefficient of aerosols can be inversed by the new method proposed in this paper. The new method can eliminate the gas molecules backscatter single in the Mie scattering echo, thus effectively reduces the impact of the number density heterogeneity of atmospheric molecular. At the end of the paper, the summer and autumn cirrus clouds' extinction-to-backscatter ratio statistics of Beijing in 2012 that reversed by the method mentioned above is presented.