Gordon H R, Brown J W, Evans R H
Appl Opt. 1988 Mar 1;27(5):862-71. doi: 10.1364/AO.27.000862.
For improved analysis of Coastal Zone Color Scanner (CZCS) imagery, the radiance reflected from a planeparallel atmosphere and flat sea surface in the absence of aerosols (Rayleigh radiance) has been computed with an exact multiple scattering code, i.e., including polarization. The results indicate that the single scattering approximation normally used to compute this radiance can cause errors of up to 5% for small and moderate solar zenith angles. At large solar zenith angles, such as encountered in the analysis of high-latitude imagery, the errors can become much larger, e.g.,>10% in the blue band. The single scattering error also varies along individual scan lines. Comparison with multiple scattering computations using scalar transfer theory, i.e., ignoring polarization, show that scalar theory can yield errors of approximately the same magnitude as single scattering when compared with exact computations at small to moderate values of the solar zenith angle. The exact computations can be easily incorporated into CZCS processing algorithms, and, for application to future instruments with higher radiometric sensitivity, a scheme is developed with which the effect of variations in the surface pressure could be easily and accurately included in the exact computation of the Rayleigh radiance. Direct application of these computations to CZCS imagery indicates that accurate atmospheric corrections can be made with solar zenith angles at least as large as 65 degrees and probably up to at least 70 degrees with a more sensitive instrument. This suggests that the new Rayleigh radiance algorithm should produce more consistent pigment retrievals, particularly at high latitudes.
为了更好地分析海岸带彩色扫描仪（CZCS）图像，利用精确的多次散射代码（即包括偏振）计算了在无气溶胶情况下从平面平行大气和平坦海面反射的辐射率（瑞利辐射率）。结果表明，通常用于计算该辐射率的单次散射近似对于小到中等太阳天顶角可能会导致高达5%的误差。在大太阳天顶角时，如在高纬度图像分析中遇到的情况，误差可能会变得更大，例如在蓝波段大于10%。单次散射误差也会沿各扫描线变化。与使用标量传输理论（即忽略偏振）的多次散射计算结果相比，发现在小到中等太阳天顶角时，与精确计算相比，标量理论产生的误差大小与单次散射近似产生的误差大致相同。精确计算可以很容易地纳入CZCS处理算法中，并且为了应用于未来具有更高辐射灵敏度的仪器，开发了一种方案，利用该方案可以轻松且准确地将表面压力变化的影响纳入瑞利辐射率的精确计算中。将这些计算直接应用于CZCS图像表明，对于太阳天顶角至少为65度的情况可以进行精确的大气校正，使用更灵敏的仪器时可能至少可达70度。这表明新的瑞利辐射率算法应该能产生更一致的色素反演结果，特别是在高纬度地区。
