Research On Infrared Radiative Characteristics Of The Non-lte Atmosphere

With the rapid development of infrared optical technology, the infrared radiation characteristics of the earth atmospheric background became a hot spot in the field of space-based target detection and satellite remote sensing detection, etc. In order to research the spectral characteristics of the atmospheric background under typical atmospheric conditions, appropriate radiative transfer model must be established and radiative transfer equation should be solved. However, most of radiative transfer models at present are generally based on local thermodynamic equilibrium(LTE) assumption. In addition, plane-parallel atmosphere theory is applied. But above approximate processing methods are different with the actual atmosphere situation, including the actual atmospheric thermodynamic state and geometric model. Because due to the small air density and low pressure, the collision frequency between molecules is small in the upper atmosphere, which resulting that the atmosphere molecules can’t reach equilibrium timely by exchanges of energy, and the actual atmosphere is spherical in fact. Therefore, in order to build a more precise atmospheric radiative transfer model, it is necessary to study the atmospheric non local thermodynamic equilibrium(NLTE) effect of thermal radiation transfer in the upper atmosphere.In this dissertation, the transmission characteristics of infrared radiation in NLTE atmosphere has been simulated and researched based on the basic theory of atmospheric radiation transmission. And the main research work focuses on the following aspects:1.The absorption of infrared radiation caused by atmosphere components was introduced in detail, and mainly including strong absorption bands of H2 O, CO2 and O3 molecules.2.The atmospheric molecular NLTE radiation mechanism was studied from molecular structure. The expression of energy level population and source function were derived in classic NLTE situations. The expression of vibrational temperature was presented. And the deviation between vibrational temperature of energy levels and kinetic temperature was calculated and analyzed.3.The solution method of radiative transfer equation in spherical atmosphere was analyzed emphatically. The atmosphere NLTE limb transmittance and radiance under typical atmosphere conditions were calculated based on Hemi-Sphere Adding method proposed in our previous work. And the model was validated by SHARC results. The atmosphere NLTE limb transmittance and radiance of H2 O, CO2 and O3 molecules under typical atmosphere conditions were calculated and analyzed as well.4. The simulation software of NLTE infrared radiation characteristics of atmospheric background was developed. Based on the MATLAB platform, the atmospheric NLTE limb infrared radiation calculation software was programmed. With input of atmosphere parameters and geometry conditions, the atmospheric molecular vibrational temperature, NLTE limb transmittance and radiation data and images were output. And the software has the advantages of friendly interface and full-functionality, which can calculate the atmosphere NLTE and LTE radiance in each calculation and it is very convenient to analyze the atmospheric NLTE radiation effects compared with other NLTE models.