Fig. 1. Schematic diagram of laser heterodyne principle

Fig. 2. Flow chart of water vapor column concentration inversion

Fig. 3. Structure diagram of laser heterodyne spectrometer system

Fig. 4. Convolution diagram of spectral signal and instrument line shape function

Fig. 5. The instrument line-shape function of laser heterodyne spectrometer

Fig. 6. SNR of 3.66 μm laser heterodyne spectrometer

Fig. 7. The Jacobian value of water vapor in 3.66 μm

Fig. 8. The priori and the retrieved profile of water vapor

Fig. 9. Laser heterodyne spectral signal and the retrieval fitting

Fig. 10. Measured results of water vapor column concentration on 22 and 23 May

Fig. 11. Correlation analysis of water vapor column concentration between laser heterodyne spectrometer and Fourier transform spectrometer