Anomalous propagation
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In Radio:
Anomalous propagation includes different forms of electromagnetic wave propagation that are not encountered in a standard atmosphere. While technically the term includes propagation with larger losses than in standard atmosphere, in practical applications it is most often meant to refer to cases when signal propagates beyond normal radio horizon.
Anomalous propagation can be subdivided as follows:
- Multipath propagation near the Earth's surface
- Unusual refraction profiles in the troposphere due to atmospheric inversions (e.g. surface-based ducting, evaporation ducting, elevated ducts)
- Scattering from irregularities in the troposphere (troposcatter)
- Scattering from the ionosphere due to meteors
- Refraction in the ionized regions and layers of the ionosphere
- Reflection from the ionosphere
References: W.L.Patterson, C.P.Hattan, G.E.Lindem, R.A.Paulus, H.V.Hitney, K.D.Anderson, A.E.Barrios. Technical Document 2648. Engineer's Refractive Effects Prediction System (EREPS) Version 3.0. May 1994. San Diego, CA.
Doppler Weather Radar:
Anomalous propagation refers to false radar echoes usually observed when calm, stable atmospheric conditions direct the radar beam toward the ground. Also caused by other phenomenon such as thunderstorms, ground debris, bird flocks, ocean reflections, and others.
