The propagation of energy when it arrives at a destination via a path significantly different from the normally expected path.
The term is usually applied to the transmission of various forms of energy through the atmosphere when, in addition to the line-of-sight path, the energy is refracted by density discontinuities at one or more levels in atmosphere. Therefore, it propagates to a point that could not be reached via a line-of-sight path. In radio and radar studies, it refers to the abnormal refraction of a beam of radio energy, usually applied to superstandard propagation rather than to substandard propagation. In either case, anomalous propagation results from an unusual vertical distribution of temperature and moisture in the atmosphere.
The anomalous propagation of sound refers to the downward refraction of an oblique sound wave from an explosion, the refraction occurring in the region of increasing temperature with height in the lower mesosphere. The anomalous propagation of sound has been used as a method for determining upper air temperatures and winds.
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use