MODTRAN5中不同光谱分辨率带模式对计算大气吸收带背景辐射的影响

Influence of Improved MODTRAN5 Band Model Spectral Resolution on Background Radiation Calculation in Molecular Absorption Region

大气吸收波段对于从卫星高度向下探测空间亮目标有特殊的优势,使用辐射传输模式MODTRAN5模拟计算了中红外大气吸收波段不同光谱分辨率100 km高度大气背景辐亮度的变化。将三个波段不同分辨率的结果平滑到统一分辨率进行对比表明:4.3 mm不同光谱分辨率相对误差最大可超过10%;其中0.2 cm^(-1)光谱分辨率的计算结果与精确的逐线积分最为接近;3.2μm与2.7μm波段不同光谱分辨率的计算结果误差较小,其中2.7μm波段最大误差小于5%。进一步将MODTRAN4和MODTRAN5的1cm^(-1)、5 cm^(-1)光谱分辨率计算结果与逐线积分做了比较,表明使用MODTRAN5的低光谱分辨率计算4.3 mm波段的辐亮度可能产生较大误差。

The molecular absorption region has a great advantage on space target detection from the altitude of satellite. The background radiation of the molecular absorption band in infrared region was calculated using the moderate spectral resolution radiative transport model MODTRAN5 at different spectral resolutions. All resolution results of three absorption bands were convolved with the same spectral response function to make an intercomparison and the results show that： for the 4.3 μm region the maximum relative deviation exceeded 10% and the 0.2 cm-1 spectral resolution results had an excellent agreement with the line-by-line calculation; the relative deviation between high and low resolution is rather small at 3.2 μm and 2.7 μm region; the maximum deviation at 2.7 μm region was below 5%. Further intercomparison was carried out between the deviation of MODTRAN4 and MODTRAN5 at 1 cm-1, 5 cm-1 spectral resolution respectively and the line- by-line calculation and the results show that the low resolution MODTRAN5 radiation calculation may result in considerable bias at 4.3μm region.