That warmest part of a slope above a valley floor lying between the layer of cold air that forms over the valley floor on calm, clear nights and the cold hilltops or plateaus. The air flowing down the
slopes is warmed by mixing with the air above ground level and to some extent also by adiabatic compression. The frostless zone is not a fixed belt but varies in level from night to night and season to season according to the initial temperature, the length of the night, and the clearness of the sky. Its lower limit is sometimes clearly marked by the upper limit of frost damage to crops, following the hillsides at a small angle to the horizontal. (Also called thermal belt, thermal zone, green belt, verdant zone.)
Maximum depth of frozen ground during the winter. The term may refer to an individual winter, to an average over a number of years, or to the greatest depth since observations began. The frost line va
ries with the nature of soil and the protection afforded by vegetal ground cover and snow cover, as well as with the amount of seasonal cooling.
Any mound-shaped landform produced by ground freezing combined with Accumulation of Ground Ice due to groundwater movement or the migration of soil moisture. Various types of Frost Mounds, (e.g., fros
t blisters, icing blisters, palsas and Pingos) can be distinguished on the basis of their structure and duration, and the character of the Ice contained in them.
A conical mound on a land surface, caused by the freezing of water in the ground. It is a product of frost heaving, but is unusual in that it requires a great concentration of water in a relatively sm
all subsurface volume. Usually a frost mound is of seasonal duration. (Also called ice mound, ground ice mound.)
Any mound-shaped landform produced by ground freezing combined with accumulation of ground ice due to groundwater movement or the migration of soil moisture.
Any mound-shaped landform produced by ground freezing combined with accumulation of ground ice due to groundwater movement or the migration of soil moisture
Is the temperature at which water vapor saturates from an air mass into solid usually forming snow or frost. Frost point normally occurs when a mass of air has a relative humidity of 100%.
An instrument similar to the dewpoint hygrometer, but especially suited for low frost points. The strong cooling necessary for these measurements is provided either by multistage Peltier devices or by
evaporating low-boiling-point (cryogenic) fluids like liquid nitrogen. Using this technique, frost points down to -100C can be measured. Electrical resistance wires are used to provide heating.
Methods of a passive or active nature that serve to reduce the damage to plants during a frost period. Passive methods include variety selection, site selection, and planting date. Active methods incl
ude heaters, fans, flooding, sprinkling, windbreaks, mulching, etc.
A false annual growth ring in the trunk of a tree, due to out-of-season defoliation by frost and subsequent regrowth of foliage. A frost ring is identified by a thin light ring within the annual growt
h ring.
The mechanical disintegration of rock by the pressure of the freezing of water in pores and along grain boundaries. Freezing of the water drawn between the grains by various particle surface forces ex
erts sufficient differential pressure to loosen and separate the grains. Frost Shattering may be the dominant weathering process in high mountain regions, particularly in areas with frequent Freeze-Thaw Cycles and heavily jointed and weak rock types.