Author: Affiliation: In many applications an accurate description is required of light...

6. Radiative Transfer in Coupled Media: Atmosphere/Snow/Ice/Ocean
S. Stamnes, B. Hamre, W. Li, J. J. Stamnes, and K. Stamnes
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
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.