Fig. 1. Schematic diagram of airborne IPDA lidar detection

Fig. 2. Schematic of IPDA lidar system

Fig. 3. Schematic diagram of IPDA lidar transceiver system

Fig. 4. Images of clouds taken by onboard camera. From left to right, it is seen that cloud cover increases successively and clouds become thicker

Fig. 5. Data processing flow chart

Fig. 6. Schematic diagram of target altitude calibration with airborne lidar

Fig. 7. Signals received by IPDA lidar. (a) Aliasing cloud echo signal; (b) two-layer cloud echo signal; (c) single-layer cloud echo signal; (d) ground echo signal; (e) cloud and ground echo signals

Fig. 8. Schematic diagram of cloud signal extraction method. (a) Diagrams of echo signal extraction; (b) diagrams of extracted signal with same integral range

Fig. 9. Voltage values of backscatter profile varying with height. (a) Echo signal after altitude correction; (b) comparison of first echo signal before and after altitude correction; (c) comparison of second echo signal before and after altitude correction

Fig. 10. Summary plot of IPDA lidar measurements on 2019-03-14

Fig. 11. Trends of monitor signal energy and echo signal energy of cloud signal. (a) Online monitor signal; (b) offline monitor signal; (c) online echo signal; (d) offline echo signal

Fig. 12. Diagram of relative reflectance of clouds

Fig. 13. Diagram of cloud density distribution

Fig. 14. Images of cloud cover change captured by onboard camera

Fig. 15. Comparison between trend of CO₂ column concentration on cloud measured by IPDA lidar and trend of single-point CO₂ concentration measured by in-situ measuring instrument

Fig. 16. Schematic diagram of CO₂ column concentrations on clouds