Fig. 1. Atmospheric echo spatiotemporal distribution pattern observed by lidar

Fig. 2. Fundamental principle of differential zero-crossing method. (a) Lidar echo signal; (b) first order differential signal

Fig. 3. Comparison of original and scaled lidar echo signals

Fig. 4. Flow chart of improved differential zero-crossing algorithm

Fig. 5. Zero-point clustering results. (a) Lidar echo signal; (b) cloud detection results

Fig. 6. Simulated lidar echo signal and corresponding algorithm processing results. (a) Simulated low-cloud lidar echo signal; (b) algorithm processing result of low-cloud signal; (c) simulated high cloud lidar echo signal; (d) algorithm processing result of high-cloud signal

Fig. 7. Lidar echo signal and partial cloud layer amplified signals. (a) Measured lidar echo signal；(b) amplified signal in 2.54.5 km; (c) amplified signal in 4.06.5 km; (d) amplified signal in 7.010.0 km

Fig. 8. Inversion results of improved algorithm and partial cloud layer amplified signals. (a) Algorithm processing result of lidar echo signal; (b) first cloud layer; (c) second cloud layer; (d) third cloud layer

Fig. 9. Detection results of differential zero crossing method and improved algorithm; (a) Differential zero-crossing method; (b) improved algorithm