CORRECTION OF THE FERNALD METHOD USING REAL-TIME AVERAGE LIDAR RATIOS WITH MIE-RAYLEIGH-RAMAN LIDAR

Abstract

A Mie-Rayleigh-Raman lidar system was used to invert the optical properties of aerosol and determine the lidar ratio. Subsequently, the real-time lidar ratio was used to modify the Fernald method; 1167 groups of data were used to invert the aerosol lidar ratios. We determined the average aerosol lidar ratio profile, which ranged from 30 to 45 in Nanjing, China. Because the Raman signal had a low SNR (Signal Noise Ratio) and the Raman channel was only available at night, it was not possible to make the correction using a real-time lidar ratio. Therefore, an average lidar ratio was used for the correction. The hypothetical value of the lidar ratio used in the Fernald method deviates from the actual value, which can result in errors. Furthermore, large errors can be produced when clouds are present on the lidar line. The accuracy of inversion of the aerosol optical characteristics can be significantly improved by correcting the Fernald method using the real-time lidar ratio or average lidar ratio.