绿洲边缘内外大气中水汽影响辐射传输分析

ANALYSIS OF VAPOR ON RADIATIVE TRANSFER INSIDE AND OUTSIDE OF OASIS EDGE

水汽是大气中影响辐射传输的重要因子之一，实验观测表明在绿洲边缘内外近地层大气中水汽含量存在一定的差异，因此绿洲边缘内外大气中辐射传输特性也不同．本文遇过应用MODTRAN辐射模式和“干旱环境综合研究计划95”（简称AECMP95）野外实验近地面观测资料，分析了局地大气中水汽对达到地面辐射通量密度或辐射率、透射率的影响，并与地面观测结果进行了比较，同时对绿洲边缘内外太阳辐射近红外1．55～1．7μm带和大气窗区10．2～12．0μm带大气透射率、辐射率及其随高度的变化进行了计算分析。

Vapor is one of the most important factors which affects radiative transfer in atmo-sphere. Field observated results showed that its content near surface layer was obviouslydifferent between inside and outside parts of Oasis edge. In this paper, the effects of vaporon transmittance, radiance and comparison between observation and model results werecarried by running MODTRAN model. This model was developed over past 25 years at theUS Air Force Philllips Laboratory, it can be used to calculate the transmittance and/or theradiance for a specified path through the atmosphere, the spectral region is partitioned into1 cm^(-1) bin for various radiative calculation. The data used in calculation were collectedduring Arid Environment Compressive Monitor Plan'95. At the same time, transmittancein solar nearinfrared 1. 55 - 1. 75μm band and atmospheric window 10．2 - 12．0μmbandwere calculated, vertical structure of the radiance and transmittance were also pre-sented. the results can be concluded as following five aspects: (1)Air temprature and vapormixing ratio near surface layer were obviously different between inside and outside of Oa-sis edge, the maximal values reached 3. 3℃ and 3. 3g/kg. (2)The relative error of down-ward radiation flux density between observation and model result at site D1 and O1 were8. 0％ and 8. 1％ for shortwave, 7. 5％ and 4. 9％ for longwave. (3)Vapor and aerosl aremore important factors in calculating downward radiation flux density, especialy arosol forsolar radiation and vapor for longwave radiation. (4) The discrepancy of transmittance was0. 0015 in nearinfrared 1. 55 - 1. 75μm band, 0. 0243 in atmospheric window 10. 2- 12.0μm band, the value in Gobi was bigger than that in Oasis. (5)The transmittance and radi-ance in atmospheric window 10. 2 - 12． 0μm band showed a vertical variation; Near thesurface layer, tansmittance is bigger in Gobi while radiance is bigger in Oasis, the maxi-mal discrenpancy between Gobi and Oasis edge were 0. 0427 and 0. 6083W/m^2-ster, whilethe vertical difference was getting smaller and smaller along the height.