As described in the previous two chapters, turbulence gives rise to image degradation as a result of wavefront tilt as well as random image detail displacement deriving from random changes in refractive index of the propagation channel. Because of the randomness, a statistical rather than deterministic approach characterizes turbulence. However, forward light scatter by aerosols and atmospheric particulates in general cause relatively very little wavefront distortion and tilt. Rather, they cause broad diffusion of details in the propagating image, thus generating image blur in a different fashion. These latter processes are rather steady and lack the time dynamic properties of turbulence.