A Case Study of Cirrus Cloud over Geermu City Using Two-Wavelength Polarization Lidar

A two-wavelength polarization lidar, developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences, was used to measure cirrus cloud over Geermu City from December 2013 to December 2014. In this paper, the authors first introduce the lidar structure and data type, as well as the data processing methods. Then, a particular observation case is used to discuss the characteristics of the cirrus cloud. The results showed that the cirrus cloud was located from 4.7 km to 7 km, with a small optical depth of less than 0.1. The mean lidar ratios at 532 nm and 1064 nm were 24.3 Sr and 29.9 Sr, respectively, and the color ratio was concentrated between 0.8 and 1. The depolarization ratio measured for this case of cirrus cloud varied from 0.1 to 0.4, with maximum frequency between 0.25 and 0.3. This lidar has the ability to measure cirrus cloud, and can be used to study the long-term spatial and temporal distribution of cirrus cloud over the Tibetan Plateau.