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 aviati
on weather observation, ground fog is encoded GF. 2. See radiation fog.
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 tempe
rature (grass temperature) of -0.9C (30.4F) or below. Since 1961 in Britain the statistics refer to the "number of days with grass minimum temperature below 0C" rather than to ground frost. A fuller discussion is given in McIntosh (1963).
A general term referring to all types of Ice contained in freezing and Frozen Ground. Ground Ice occurs in pores, cavities, voids or other openings in soil or rock and includes Massive Ice. It general
ly excludes Buried Ice. Ground Ice may be epigenetic or syngenetic, contemporaneous or relict, aggrading or degrading, perennial or seasonal. It may occur as lenses, wedges, veins, sheets, seams, irregular masses, or as individual crystals or coatings on mineral or organic particles. Perennial Ground Ice can only occur within Permafrost bodies.
General term used to describe all bodies of ice in the ground surface of the permafrost layer. Also called anchor ice. Some forms of ground ice include: pore ice, needle ice, ice wedge, segregated ice
, sand wedge, and ice lenses.
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. (Also calle
d subsoil ice, subterranean ice, underground ice, stone ice.)
The junction between a glacier or ice sheet and ice shelf; the place where ice starts to float. This junction normally occurs over a finite zone, rather than at a line.
The set of points separating the floating part of a glacier from the grounded part. See flotation. Usually the floating part is downstream and the grounded part is upstream. However, the 'shorelines'
of subglacial lakes are grounding lines.
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 r
ate.
Ground level enhancements (GLEs) are sudden increases in the cosmic ray intensity recorded by ground based detectors. GLEs are invariably associated with large solar flares.