The sea-surface reflectance factor ρ required for the determination of the water- leaving radiance from above-water radiometric measurements is derived from radiative transfer simulations relying on models of the sky-radiance distribution and sea-surface statistics. This work primarily investigates the impact on ρ of various sky-radiance and sea-surface models. A specific replicability analysis, restricted to the 550 nm wavelength, has been performed with the Monte Carlo code for Ocean Color Simulations (so-called MOX) accounting for the measurement geometry recommended in protocols for the validation of satellite ocean color data and commonly applied for operational measurements. Results indicate that the variability of ρ increases with wind speed and reaches the largest values for sun elevations close to the zenith or approaching the horizon. In particular, a variability up to about 2% is observed for wind speeds below 4 ms⁻¹ and sun zenith angles larger than 20°. Finally, the benchmark of the ρ values from this study with those formally determined with the Hydrolight code and widely utilized by the ocean color community, exhibits systematic differences. The source of these differences is discussed and the implications for field measurements are addressed.

中文翻译：

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海面反射系数：计算值的可复制性

确定来自水上辐射测量的离水辐射所需的海面反射系数ρ来自依赖于天空辐射分布和海面统计模型的辐射传输模拟。这项工作主要研究了各种天空辐射和海面模型对ρ的影响。已使用海洋颜色模拟（所谓的 MOX）蒙特卡罗代码执行了仅限于 550 nm 波长的特定可重复性分析，该代码考虑了卫星海洋颜色数据验证协议中推荐的测量几何结构，并通常应用于操作测量。结果表明ρ的变异性随风速增加，并在接近天顶或接近地平线时达到太阳高度的最大值。特别地，对于低于4 ms ^{-1 的}风速和大于20°的太阳天顶角，观察到高达约2%的可变性。最后，本研究中的ρ值与由 Hydrolight 代码正式确定并被海洋颜色社区广泛使用的ρ值的基准表现出系统差异。讨论了这些差异的来源，并解决了对现场测量的影响。