Radiative transfer in coupled systems

In many applications an accurate description is required of light propagation in two adjacent slabs separated by an interface, across which the refractive index changes. Such a two-slab configuration will be referred to as a coupled system. Three important examples are atmosphere-water systems [1]-[5], atmosphere-sea ice systems [6, 7], and air-tissue systems [8]. In each of these three examples, the change in the refractive index across the interface between the two slabs must be accounted for in order to model the transport of light throughout a coupled system correctly. In the second example, the refractive-index change together with multiple scattering leads to a significant trapping of light inside the strongly scattering, optically thick sea ice medium [6, 7]. For imaging of biological tissues or satellite remote sensing of water bodies an accurate radiative transfer (RT) model for a coupled system is an indispensable tool [9]-[12]. In both cases, an accurate RT tool is essential for obtaining satisfactory solutions of retrieval problems through iterative forward/inverse modeling [10]-[18]. In this review, the discussion is limited to applications based on scalar RT models that ignore polarization effects. There are numerous RT models available that include polarization effects (see Zhai et al. [19] and References therein for a list of papers), and the interest in applications relying on polarized radiation is growing.