6. Radiative Transfer in Coupled Media: Atmosphere/Snow/Ice/Ocean Systems S. Stamnes, B. Hamre, W. Li, J. J. Stamnes, and K. Stamnes Author： Affiliation： Stevens Institute of Technology 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, atmosphere-sea ice systems, and air-tissue systems. 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 the 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. 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. In both cases, an accurate RT tool is essential for obtaining satisfactory solutions of retrieval problems through iterative forward/inverse modeling. Here we describe recent developments in both scalar RT models that ignore polarization effects as well as vector radiative transfer models that include polarization. The models to be discussed here represent significant extensions of the popular discrete-ordinate radiative transfer code DISORT (Stamnes, K., S.-C. Tsay, W.J. Wiscombe and K. Jayaweera, Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media, Applied Optics, 27, 2502-2509, 1988) designed for scalar radiative transfer in uncoupled systems. Scalar models for coupled media have already been used extensively as forward models to develop inversion algorithms for atmosphere-water, atmosphere-snow-ice, and air-tissue systems. Similarly, vector RT models for coupled media have been and will be more extensively used to develop retrieval algorithms that rely on observations of polarized radiation as such data are expected to become more frequently available in the future from instruments deployed onboard Earth-orbiting satellites.