Polarized SVBRDF modeling of spatially heterogeneous sea surfaces based on the microscopic scattering mechanisms of whitecaps.

The spatial heterogeneity of sea surface reflectance poses a fundamental challenge to high-precision ocean remote sensing, as conventional homogeneous models fail to capture this complexity. We propose a polarized spatially varying bidirectional reflectance distribution function (pSVBRDF) model tailored for spatially heterogeneous sea surfaces. The sea surface is discretized into micro-elements. Four types of standard basic elements (SBEs) that dominate the optical characteristics of the sea surface are then defined, and their corresponding reflection response functions (RRFs) and transport mean free path (TMFP) are constructed. Finally, these RRFs are mapped onto the micro-elements based on local incident angle, and a physically explicit pSVBRDF is synthesized. Model validation demonstrates high accuracy when geometric effects and whitecap distribution are decoupled, while under realistic coupled conditions, it accurately reproduces features such as reflection glint and polarization dark spots. Parameter sensitivity analysis based on the structural similarity index measure (SSIM) shows that reflected intensity (I) is sensitive to wind speed (SSIM 2.896) and wind direction (SSIM 2.853). The degree of polarization (DoP) is sensitive not only to wind speed (SSIM 2.655) and direction (SSIM 2.686) but also notably to the sea-air temperature difference (SSIM 1.894). This study advances beyond traditional homogeneous BRDF models and the Lambertian assumption for whitecaps, establishing an effective reflectance model that characterizes sea surface heterogeneity and providing a key modeling tool for ocean remote sensing and target detection.