对流层低层大气气溶胶对曙暮光辐射强度及天空颜色的影响

【作者】 范学花；

【导师】 杜秉玉； 陈洪滨；

【作者基本信息】 南京气象学院 ， 大气物理学与大气环境， 2003， 硕士

【摘要】 采用离散坐标法(DISORT)辐射传输软件包UVSPEC的伪球面模式，计算了300nm～850nm波段曙暮光时期地面不同观测仰角的辐射强度和天空颜色。模式选取美国标准大气(U.S.1976)，DISORT计算取16流，考虑多次散射效应及水汽、臭氧和二氧化碳的吸收。30～100km高度范围内采用流星尘气溶胶，10～30km高度范围内采用背景平流层气溶胶，2～10km采用模式提供的对流层消光。0～2km的气溶胶消光与地面能见度有关。选取城市气溶胶类型，550nm处的气溶胶光学厚度τ分别为0.3303，0.7207，1.3072和2.0872四种情况下的曙暮光辐射强度随太阳天顶角和观测仰角的变化，分析研究了近地层大气不同气溶胶光学厚度时曙暮光全天空的辐射强度和颜色指数随太阳天顶角和观测仰角的变化。计算结果分析表明，曙暮光时天空辐射强度的红蓝光颜色指数随近地层大气气溶胶光学厚度的变化显著；当τ较小时，太阳辐射随波长的变化显著，在高仰角450nm附近有极大值，天顶方向以蓝色调为主；而在低仰角极大值向红光方向移动。当τ较大，即大气十分浑浊时，太阳辐射强度减弱而且随波长的变化不明显，这时天空色彩没有层次。在仰角(α)5°～15°范围及τ值小于1.5时，颜色指数(I_c)与气溶胶光学厚度(τ)有一定的单调关系，理论上这种关系可以用于近地层气溶胶光学厚度的反演测量。更多还原

【Abstract】 The radiance and color of the twilight sky were calculated by use of the pseudo-spherical model of DISORT (Discrete-Ordinate-method) radiative transfer software package-UVSPEC. The absorption of H2O, CO2, O3 and multiple-scattering were taken into account in the radiative transfer model. The computation employed the U.S. Standard Atmosphere 1976 for the wavelength range from 300nm to 850nm. DISORT selected 16 streams. Meteoric dust extinction was selected in 30~ 100km, background stratospheric extinction was selected in 10~30km, tropospheric extinction provided by UVSPEC was selected in 2~10km. However, the aerosol extinction in 0~2km was related to surface visibility. Radiances of four Aerosol Optical Depths (AOD) of 550nm were calculated respectively. The variations of intensity and color index (7C) during twilight at different solar zenith angles (SZA) and view elevation angles with AODs in lower atmosphere were investigated. The results showed that the red /blue color index during twilight changed evidently with AODs in lower atmosphere. When AOD was small, there was a maximum of the radiance at 450nm in the high view elevation angle. So the sky color at the zenith is blue. However, the maximum shifted to red wavelength (about 700nm) with the fall of view elevation angle. When the AOD was rather big, the radiances decreased evidently and the variations of radiance with the wavelength were not obvious. So the sky color is dull. There was a monotone relation between the color index and the AOD when the view elevation angles range from 5 degree to 15 degree and the AOD was less than 1.5. Thus, in principle, the proposed color index would be used to measure and retrieve the AOD in lower atmosphere.更多还原