Book excerpt: This book is dedicated to the formulation and solution of forward and inverse problems related to coupled media, and provides examples of how to solve concrete problems in environmental remote sensing of coupled atmosphere-surface systems. The authors discuss radiative transfer in coupled media such as the atmosphere-ocean system with Lambertian as well non-Lambertian reflecting surfaces at the lower boundary. The spectral range from the ultraviolet to the microwave region of the electromagnetic spectrum is considered, as are multi-spectral as well as hyperspectral remote sensing, while solutions of the forward problem for unpolarized and polarized radiation are discussed in detail.