Superstandard Propagation

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Superstandard Propagation

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The propagation of radio waves under conditions of superstandard refraction (superrefraction) in the atmosphere, that is, refraction by an atmosphere or section of the atmosphere in which the index of refraction decreases with height at a rate of greater than 12 N-units per 1000 feet. See standard propagation, substandard propagation. </dd>
Superstandard propagation produces a greater-than-normal downward bending of radio waves as they travel through the atmosphere, giving extended radio horizons and increased radar coverage. It results primarily from propagation through layers near the earth's surface in which the moisture lapse rate is greater than normal, or the temperature lapse rate less than normal, or both. A condition in which warn dry air moves out over a cool water surface is an example of superrefraction. A layer in which the downward bending is greater than the curvature of the earth is called a radio duct. Frequently, the general term, anomalous propagation, is used for superstandard propagation. </dd>

References

This article is based on NASA's Dictionary of Technical Terms for Aerospace Use