Fig. 1. Issues in lidar detection and data processing: ① overlap factor correction; ② cloud and aerosol layer detection; ③ data retrieval. (a) Schematic diagram of lidar detection; (b) dashed line is clear atmosphere signal, while actually observed signal is usually shown as solid line (range between triangle marks is layer and rest represents uniform atmosphere); (c) extinction coefficients retrieved from observed signal

Fig. 2. Geometric structure of lidar observation varies with distance r^[48]

Fig. 3. Overlap factor varies with laser emission angle θand telescope receiver half angle α^[48]. (a) Overlap factor varies with θ; (b) overlap factor varies with α

Fig. 4. Schematic diagram of detection by slope method and threshold method. (a) Ground-based lidar observation signal; (b) slope of ground-based lidar signal; (c) layer detection threshold of ground-based lidar (dashed line)

Fig. 5. Comparison of joint multiscale algorithm and MPLNET product for scene detection^[82]. (a) Ground-based lidar echo signal; (b) cloud layer detection results for MPLNET product; (c) cloud layer detection results for joint multiscale algorithm; (d) differences in cloud detection between two methods, where label "1", label "2", and label "3" represent common detections of both methods, unique detections of MPLNET product, and unique detections of joint multiscale algorithm, respectively

Fig. 6. Influence of boundary value selection on lidar retrieval. (a) Simulated signal of ground-based lidar; (b) true value (solid line) and retrieval value (other lines) of extinction coefficients. Dots represent boundary values selected for retrieval, and lines from left to right (excluding solid line) indicate retrieval results with boundary value deviations of -40%, -20%, +20%, and +40%, respectively

Fig. 7. Influence of lidar ratio selection on lidar retrieval. (a) Simulated signals of ground-based lidar observation; (b) true value (solid line) and retrieval value (other lines) of extinction coefficients. Lines from left to right (excluding solid line) indicate retrieval results for lidar ratios of 30, 40, 60, and 70 sr, respectively