The accurate atmospheric temperature profile retrieved from the spaceborne infrared spectra is very important data source for the evaluation of infrared engineering and the analysis of weather/climate process, especially for the place where other high-quality data sources are not available, such as the ocean and desert. Most of current algorithms are severely dependent on historical information to constrain retrieval process, which would encounter the issues of accuracy and stability in the wild field as mentioned above. To resolve this contradiction, the Gauss-Newton iteration method with Tikhonov regularization is proposed in this paper. To constrain the iteration by keeping the balance between norm of solution and norm of spectra residual, the method can select the initial profile and regularization matrix that are independent with historical information. Besides, the information content theory is employed to select the appropriate spectral channels to achieve optimal solution. The simulation experiment is conducted to validate the proposed method. The results prove that the effective retrieval profile can be achieved very quickly and is insensitive to the initial profile or spectra noise, which demonstrates its good performance.
In order to study the variation law of radiation characteristics of high temperature gas with altitude in medium and low altitude environment, the spectral radiation characteristics of three mixed gases containing H2O, CO2 and CO at different temperatures and pressures were calculated by LBL (Line by line) method, so as to analyze the corresponding changes of spectral radiation intensity of high temperature gas with the change of overall temperature and pressure, and explain the reason why the radiation spectrum changes with altitude. The results showed that the influence of temperature on the radiation intensity was more significant than that of pressure; at the same time, with the decrease of temperature, the peak value of spectral radiation gradually moved to the middle wave band, and the radiation intensity at 4.3 μm, which is the radiation band of CO2, and 4.7 μm, which is the radiation band of CO, gradually increased. However, due to the greater sensitivity of CO to the change of pressure, the relative radiation intensity at 4.7 μm after the pressure was reduced.
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