There are two regular methods to calculate infrared atmospheric transmittance, including empirical formula and professional software. However, it has large deviations to use empirical formula. It is complicated to use professional software and difficult to apply in other infrared simulative system. Therefore, based on measured atmospheric data in some area for many years, article used the method of molecular single absorption to calculate absorption coefficients of water vapor and carbon dioxide in different temperature. Temperatures, pressures, and consequent scattering coefficients which distributed in different high were fitted with analysis formula according to different months. Then, it built simulative calculation model of atmospheric transmittance of infrared radiation. The simulative results are very close to accuracy results calculated by user-defined model of MODTRAN. The method is easy and convenient to use and has certain referent value in the project application.
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