This article analyzes the atmospheric transmittance in the infrared band under different atmosphere conditions based on the MODTRAN software. Firstly, the atmospheric transmittance in the infrared band under two different atmospheric types, cold-dry and warm-wet, are calculated. Subsequently, the effect of H2O, CO2 and O3 molecules on the atmospheric transmittance in the infrared band are analyzed. Secondly, the differences in atmospheric transmittance at different altitudes (troposphere, stratosphere, mesosphere, thermosphere) in the infrared band are calculated, and the effects of H2O, CO2 and O3, CH4 and N2 on atmospheric transmittance and their variation patterns are analyzed. Finally, the influence of different aerosol types on atmospheric transmittance is calculated and analyzed, mainly considering molecular scattering and five different types of aerosol scattering. Conclusion, i) The total atmospheric transmittance of cold-dry atmospheres is higher than that of warm-wet atmospheres. The main factors influencing the difference in atmospheric transmittance between the two are H2O and O3. ii) Atmospheric transmittance varies with altitude, with the most dramatic changes with altitude being in the troposphere and stratosphere. The factors that have a greater influence on the atmospheric transmittance in the troposphere are H2O and CO2; CO2, O3 and CH4 have great influence on stratospheric atmospheric transmittance; The atmospheric transmittance of the mesosphere has little change, almost 1. The fluctuation of its transmittance curve is mainly affected by O3; The atmospheric transmittance of thermosphere is almost 1; N2 has little effect on atmospheric transmittance. iii) The influence of molecular scattering on atmospheric transmittance is negligible, while aerosol scattering has a great influence on atmospheric transmittance; Aerosol scattering at 9 μm has the greatest influence on atmospheric transmittance. The research results of this paper have certain guiding significance for the design and performance evaluation of infrared systems under different application conditions.
