A Basic Study on the Estimation of Ocean Wind Vector Using Reflected Radiance and Polarization Data

在这项研究中，我们已经作出了分析的机载POLDER数据在海洋上的多次散射模式。假设一个具有Cox-Munk型反射海面的大气-海洋系统，用加法和乘法计算了几种不同大气模式的反射率和线偏振度，包括多次散射和反射的贡献。结果表明：1）海洋气溶胶模型不适合于Medimar数据，而Junge型气溶胶模型（3 < v < 5）能够满足观测到的偏振特性; 2）基于多次散射计算，首次实现了反射率和线偏振度的图像重建。我们发现，在观测到的反射率和偏振图像中的许多特征可以通过假设两层大气模型在理论上重建，3）各向同性的Cox-Munk模型应该被拒绝，因为它不能解释观测到的反射率曲线相对于观测天顶角reta = 0在垂直平面上。各向异性的Cox-Munk模式可以解释这种不对称性，可以用来反演地面风场。在此需要指出的是，对这种模式进行多次散射分析，对于准确地估计地面风场是必要的。5）关于偏振的一个主要问题是，在主平面对称位置上存在两个偏振极小点，这一问题有待于进一步的解释。

In this study we have made an analysis of the airborne POLDER data over the ocean by a multiple scattering model. Assuming an atmosphere-ocean system with a Cox-Munk type reflecting sea surface, the reflectance and degree of linear polarization, including contributions from multiple scatterings and reflections have been computed by using the adding and doubling method for several different atmospheric models. Our results based on this study are summarized as follows :1) We found the oceanic aerosol model is not an appropriate aerosol model for Medimar data, but Junge type aerosol model with 3 < v < 5 is able to satisfy the observed polarization characteristics.2) Based on the multiple scattering computations, the image reconstruction for the reflectance and degree of linear polarization was made, for the first time. We showed that many features in the observed reflectance and polarization images can be theoretically reconstructed by assuming a two layrs atmospheric model, composing of Rayleigh and aerosol particles with a Cox-Munk sea surface layr.3) An isotropic Cox-Munk model should be rejected on the ground that it fails to explain the asymmetry in the observed reflectance curve with respect to the viewing zenith angle rheta=0 in the perpendicular plane. An anisotropic Cox-Munk model can explain such the asymmetry and it should be used in retrieving the surface wind field instead. We should point out here that the multiple scattering analysis for such a model is necessary for estimating the surface wind field accurately.5) As a major unsolved problem conceming with polarization, a clear explanation of two polarization minimum points in a symmetric location to the principal plane is left in future.