A fine calibration of the depolarization ratio is required for a detailed interpretation of lidar-observed polar stratospheric clouds. We propose a procedure for analyzing data by using atmospheric depolarization lidar. The method is based on a plot of δT versus (1 - RT-1), where δT is the total depolarization ratio and RT is the total backscattering ratio. Assuming that there are only spherical particles in some altitude ranges of the lidar data, the characteristics of the plot of δT versus (1 - RT-1) lead to a simple but effective calibration method for δT. Additionally, the depolarization of air molecules δm can be determined in the process of δT calibration. We compared determined values with theoretically calculated values for the depolarization of air to test the proposed method. The δm value was calculated from the lidar data acquired at Ny-Ålesund (79 °N, 12 °E), Svalbard in winter 1994–1995. When only sulfate aerosols were present on 24 December 1994, δm was 0.46 ± 0.35%. When the particles consisted of sulfate aerosols and spherical particles of polar stratospheric clouds on 4 January 1995, δm was 0.45 ± 0.07%. Both δm values were in good agreement with the theoretically calculated value, 0.50 ± 0.03%.
© 2001 Optical Society of America
Original Manuscript: September 29, 2000
Revised Manuscript: July 1, 2001
Published: December 20, 2001
Hiroshi Adachi, Takashi Shibata, Yasunobu Iwasaka, and Motowo Fujiwara, "Calibration method for the lidar-observed stratospheric depolarization ratio in the presence of liquid aerosol particles," Appl. Opt. 40, 6587-6595 (2001)