Method to evaluate errors of Mie-Lidar in the transition zone with a dual CCD laser system

Abstract

Mie Scattering Light Detection and Ranging (Mie-Lidar) is the most frequently used tool for obtaining the vertical profile of aerosol extinction coefficients. However, Mie-Lidar has an area that is not fully overlapping (called a transition zone) several hundred meters above the ground. There is uncertainty, although a geometric overlap factor (GOF) correction is normally used. To specifically evaluate the error of Mie-Lidar in the transition zone, a dual charge-coupled device (CCD) laser system (DCLS) is developed in this study. Multiple joint measurements as well as a continuous detection experiment are conducted. The extinction coefficient profiles obtained with the DCLS and Mie-Lidar are compared. The results indicate that the extinction coefficients are nearly consistent above the transition zone, and Pearson’s correlation coefficient remains above 0.9. However, the extinction coefficients have specific differences in the transition zone, and the linear fit results are relatively bad. The average relative difference of the extinction coefficients between the Mie-Lidar and DCLS is nearly 20%. Compared Mie-Lidar, the blind zone of the DCLS is merely approximately 8 m. The DCLS shows more details of the near-surface atmosphere, and its spatial resolution of up to 1 × 10–3 m can provide a useful reference for Mie-Lidar. The DCLS contributes to obtaining a more accurate vertical distribution of aerosols in the atmospheric boundary layer.