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Section G G index 341-349 of 425 terms
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ground-controlled approach—(Commonly abbreviated GCA.) A system for the precise control of the approach and landing of aircraft by an operator on the ground. Precision approach radar is employed to view the aircraft, and the radar operator “talks” the pilot down by giving him his position and suggested corrections for maintaining the “perfect approach.” Currently, GCA is a required facility at an all-weather airport. If perfectly operated, this system would ensure safe landing under zero ceiling and visibility conditions; however, to provide a safety factor, GCA minimums are prescribed at nearly all installations.
ground data—Same as ground truth.
ground discharge—Same as cloud-to-ground discharge.
ground flash—Same as cloud-to-ground flash or cloud-to-ground discharge.
ground flux—The transport of an atmospheric quantity into or out of the ground. The most common example is the transport of sensible heat into the ground due to radiative heating of the ground surface.
ground fog—1. According to U.S. weather observing practice, a fog that hides less than 0.6 of the sky and does not extend to the base of any clouds that may lie above it. As an obstruction to vision in an aviation weather observation, ground fog is encoded GF. 2. See radiation fog.
ground frost—1. In British usage, a freezing condition injurious to vegetation, which is considered to have occurred when a minimum thermometer exposed to the sky at a point just above a grass surface records a temperature (grass temperature) of −0.9°C (30.4°F) or below. Since 1961 in Britain the statistics refer to the “number of days with grass minimum temperature below 0°C” rather than to ground frost. A fuller discussion is given in McIntosh (1963). See frost. 2. See frozen ground.
McIntosh, D. H., 1963: The Meteorological Glossary, Her Majesty's Stationery Office, London, p. 12.
ground ice mound—Same as frost mound.
ground ice—(Also called subsoil ice, subterranean ice, underground ice, stone ice.) A body of clear ice in frozen ground. Ice of this nature is most commonly found in more or less permanently frozen ground (permafrost) and may be of sufficient age to be termed fossil ice. Compare frost mound, icing.
Muller, S. W., 1947: Permafrost, or Permanently Frozen Ground, and Related Engineering Problems, p. 217.
ground inversion—An air layer with its base at the ground surface and in which temperature increases with height. These often form at night over land under clear skies and are statically stable. See inversion, lapse rate.
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