Fig. 1. Energy level of the hyperfine structure of the D2 line of ⁸⁷Rb atom

Fig. 2. Absorption cross-section of the D2 line of ⁸⁷Rb atom, the zero optical frequency corresponds to 780.24 nm

Fig. 3. Transmittances of ⁸⁷Rb absorption cell under different temperatures with a length of 63 mm

Fig. 4. Principle of ⁸⁷Rb cell discriminator. (a) Principle of spectral separation; (b) dependencies of the Mie scattering and Rayleigh scattering transmittances on the temperature of the ⁸⁷Rb absorption cell; (c) relationship between the spectral discrimination ratio and the temperature of the ⁸⁷Rb absorption cell

Fig. 5. Relative error of the noise-induced error after ignoring T_a (T_a=0) under different temperatures

Fig. 6. Simulated profiles of the atmospheric backscattering coefficients

Fig. 7. Simulated LiDAR curves. (a) Mixed channel LiDAR curve; (b) molecular channel LiDAR curve; (c) signal-to-noise ratio of the two channels

Fig. 8. Retrieved aerosol backscattering coefficient with noise

Fig. 9. Relative errors of the aerosol backscattering coefficient ignoring $T_{\mathrm{a}}$ ($T_{\mathrm{a}}=\mathrm{0}$) and considering $T_{\mathrm{a}}$ ($T_{\mathrm{a}}\ne \mathrm{0}$) with different temperatures (signal-to-noise ratio of the mixed channel at 6 km is 20 dB)

Fig. 10. Impact of temperature disturbance on the transmittance at different temperatures. (a) Distribution of T_a under temperature disturbance; (b) distribution of T_m under temperature disturbance; (c) relative error of $T_{\mathrm{a}}$ under temperature disturbance; (d) relative error of T_m under temperature disturbance

Fig. 11. Simulation results of the error term under temperature disturbance. (a) T_a error term; (b) T_m error term

Fig. 12. Relative error of the retrieved backscattering coefficient

Fig. 13. Relative errors of transmittance due to the frequency fluctuation at different temperatures. (a) Relative error of $T_{\mathrm{a}}$; (b) relative error of $T_{\mathrm{m}}$

Fig. 14. Simulation results of the backscattering coefficient with frequency fluctuation at different temperatures. (a) 65 ℃; (b) 70 ℃; (c) 75 ℃; (d) 80 ℃

Fig. 15. Simulation results of the backscattering coefficient under different temperatures, simulation parameters: ±1 ℃ temperature fluctuation, 100 MHz frequency fluctuation, 20 dB SNR at 6 km for the mixed channel

Table 1. MC simulation parameters for the HSRL system