研究大气偏振光谱在太阳天顶角SZA、 观测天顶角VZA和相对方位角RAA构成的观测几何变化时的特征。 采用离散坐标法求解大气矢量辐射传输方程, 结合真实大气环境与结构参数, 以MODTRAN太阳参照光谱仿真大气层顶初始光谱, 考虑下垫面反照、 气溶胶垂直分层与成分混合比及痕量气体吸收的影响, 仿真计算相对方位角为0°和90°时0.4~3 μm波段大气偏振光谱, 丰富大气偏振光谱信息。 仿真结果表明: (1)相对方位角为0°时, 偏振度DoP和Q/I随SZA的变化分别呈“V形”和倒“U”形, U/I很微弱, 量级低于10-7, V/I在任何观测几何下都很微弱; (2)晨暮时段, 若太阳不在视场内, 大气偏振度在波长0.51和2.75 μm附近为极大值, 在1.5 μm附近为极小值。 因此, 在不同的观测几何条件下, 选择相应的波段和偏振信号, 将有利于实体目标探测。

Study on polarized skylight spectral characters while observation geometry changing in different solar zenith angles (SZA), viewing zenith angles (VZA) or relative azimuth angles (RAA). Simulation calculation of cloudless daylight polarimetric spectrum is realized based on the solver, vector discrete ordinate method, of radiative transfer equation. In the Sun’s principal and perpendicular plane, the spectral irradiance data, varying at wavelengths in the range between 0.4 and 3 μm, are calculated to extend the atmospheric polarization spectral information under the conditions: the MODTRAN solar reference spectrum is the only illuminant source; the main influencing factors of polarized radiative transfer include underlying surface albedo, aerosol layers and components, and the absorption of trace gases. Simulation analysis results: (1) While the relative azimuth angle is zero, the magnitude of spectrum U/I is lower than 10-7 and V/I is negligible, the degree of polarization and the spectrum Q/I are shaped like the letter V or mirror-writing U. (2) In twilight, when the Sun is not in FOV of the detector, the polarization of the daytime sky has two maximum near 0.51 and 2.75 μm, and a minimum near 1.5 μm. For arbitrary observation geometry, the spectral signal of V/I may be ignored. According to observation geometry, choosing different spectral bands or polarized signal will be propitious to targets detection.