Cryosphere glossary
freezeback
refreezing of thawed materials.
freezing (of ground)
the changing of phase from water to ice in soil or rock.
freezing degree-days
a measure of how cold it has been and how long it has been cold; the cumulative fdd is usually calculated as a sum of average daily degrees below freezing for a specified time period (10 days, month, season, etc.).
freezing drizzle
drizzle, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight.
freezing front
the advancing boundary between frozen (or partially frozen) ground and unfrozen ground.
freezing index
the cumulative number of degree-days below 0 degrees Celsius for a given time period.
freezing point
(1) the temperature at which a pure liquid solidifies under atmospheric pressure (2) the temperature at which a ground material starts to freeze.
freezing pressure
the positive pressure developed at ice-water interfaces in soil as it freezes.
freezing rain
rain, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight.
freezing-point depression
the number of degrees by which the freezing point of an earth material is depressed below 0 degrees Celsius.
friable permafrost
permafrost in which the soil particles are not held together by ice.
friendly ice
from the point of view of the submariner, an icey canopy containing many large ice skylights or other features which permit a submarine to surface; there must be more than ten such features per 37 kilometers (30 nautical miles) along the submarine's track.
front
in meteorology, generally, the interface or transition zone between two air masses of different density; since the temperature distribution is the most important regulator of the atmosphere density, a front almost invariably separates air masses of different temperature; when warmer air replaces the colder, it is a warm front, and vice-versa.
frost
the condition which exists when the temperature near the earth's surface and earth-bound objects falls below freezing (0 degrees Celsius or 32 degrees Fahrenheit).
frost action
the process of alternate freezing and thawing of moisture in soil, rock and other materials, and the resulting effects on materials and on structures placed on, or in, the ground.
frost blister
a seasonal frost mound produced through doming of seasonally frozen ground by a subsurface accumulation of water under elevated hydraulic potential during progressive freezing of the active layer.
frost boil
a small mound of soil material, presumed to have been formed by frost action.
frost bulb
a more or less symmetrical zone of frozen ground formed around a buried chilled pipeline or beneath or around a structure maintained at temperatures below 0 degrees Celsius.
frost creep
the net downslope displacement that occurs when a soil, during a freeze-thaw cycle, expands normal (perpendicular) to the ground surface and settles in a nearly vertical direction.
frost flowers
crystals of ice that form when water vapor becomes a solid (bypassing the liquid phase) and deposits itself on the sea ice surface; frost flowers roughen the surface and dramatically affect its electromagnetic signal.
Image
Close-up view of frost flowers.
Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory