Fig. 1. Energy contribution chart of mid-infrared spectroscopy

Fig. 2. Sensitivity of near infrared and mid-infrared spectroscopy to ¹³CO₂. (a) Near infrared band; (b) mid-infrared band

Fig. 3. Sensitivity of mid-infrared spectroscopy to changes in CO₂ concentration. (a) Spectral variation; (b) spectral difference

Fig. 4. Influence of ¹³CO₂ in atmospheric CO₂ on the spectrum

Fig. 5. mid-infrared spectra under different ¹³CO₂ volume fractions

Fig. 6. CO₂ weight function in mid-infrared with height

Fig. 7. Sensitivity of mid-infrared spectroscopy to environmental parameters. (a) Sensitivity of spectrum to the reflectance of the earth's surface; (b) sensitivity of spectrum to the temperature profile; (c) sensitivity of spectrum to water vapor profile; (d) sensitivity of spectrum to aerosol; (e) sensitivity of spectrum to nitrous oxide profile

Fig. 8. Influence of CO₂ concentration changes on mid-infrared spectroscopy. (a) Spectral diagram; (b) difference graph

Fig. 9. Schematic diagrams of the threshold value of the mid-infrared spectrum changing with the environmental profile. (a) Temperature profile accuracy requirement; (b) water vapor profile accuracy requirement; (c) requirement for the accuracy of nitrous oxide profile; (d) requirement for instrument signal-to-noise ratio

Table 1. Analysis of the changes of mid-infrared radiance caused by different influencing factors