Specular-point flow on a stationary wave-like random surface with respect to a reference frame moving with a source-observer is described. The time rate of change of specular point densities and the differential changes caused by creations and annihilations are used to calculate the divergence of the mean flow field. The divergence has been integrated, and both mean flow and mean velocity fields have been calculated. The flow pattern is particularly complex when the source-observer motion includes a vertical component. In such a case, there is a small but nonzero vertical component of flow, and specular points at extremal surface heights may flow in opposite directions to the major flow which occurs near the mean surface plane.
James E. Seltzer, "Flow of specular points on a random wave-like surface," J. Opt. Soc. Am. 63, 813-819 (1973)