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(1) combined processes (such as sublimation, fusion or melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field; also used to express the quantity lost by these processes (2) reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches.

the area of a glacier where more glacier mass is lost than gained.

depressions in the snow surface caused by the sun or warm, gusty wind.

mound or layer of moraine in the ablation zone of a glacier; the rock has been plucked from the mountainside by the moving glacier and is melting out on the ice surface.

period during which glaciers lose more mass than they gain; usually coincides with summer.

area or zone of a glacier where snow and ice ablation exceed accumulation.

the difference, taken without regard to sign, between the values of two variables

the difference between the measured or inferred value of a quantity and its actual value.

(1) the ratio of the mass of water vapor to the volume occupied by a mixture of water vapor and dry air (2) mass of water contained in a unit volume of moist air.

growth of a cloud or precipitation particle by the collision and union of a frozen particle (ice crystal or snowflake) with a super-cooled liquid droplet which freezes on impact.

all processes by which snow or ice are added to a glacier, this is typically the accumulation of snow, which is slowly transformed into ice; other accumulation processes can include avalanches, wind-deposited snow, and the freezing of rain within the snow pack.

area of a glacier where more mass is gained than lost.

period during which a glacier gains more mass than it loses; usually coincides with winter.

area of a glacier where more mass is gained than lost.

the extent to which the readings of an instrument approach the true value of the calculated or measured quantities, supposing that all possible corrections are applied.

rain or snow containing acidic substances, resulting from the atmospheric pollution mainly with sulfur and nitrogen; acid precipitation has a lower pH than unpolluted rain.

a foundation pile on which a cold air refrigeration system has been installed to remove heat from the ground.

special design and construction methods used for engineering works in permafrost areas where permafrost degradation cannot be prevented.

an ice wedge that is growing as a result of repeated (but not necessarily annual) winter cracking.

the layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost; also known as seasonal frost.

a foundation pile on which a liquid coolant refrigeration system has been installed to remove heat from the ground.

a mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of present movement.

the process by which characteristic landforms are currently developing as a result of thawing of ice-rich permafrost or melting of massive ice.

a general term referring to several forms of slope failures or failure mechanisms commonly occurring in the active layer overlying permafrost.

the thickness of the layer of the ground that is subject to annual thawing and freeing in areas underlain by permafrost.

the tensile or shear strength which has to be overcome to separate two objects that are bonded together by ice.

the process by which two objects are bonded together by ice formed between them.

when a mountain glacier's terminus extends farther downvalley than before; glacial advance occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.

the horizontal transfer of air mass properties by the velocity field of the atmosphere.

fog which forms in the lower part of a warm moist air mass moving over a colder surface (land or water).

non-gaseous substances, divided into solid particles or liquid droplets, held in suspension in the atmosphere.

the additional ground ice formed as a direct result of permafrost aggradation.

the cumulative number of degree-days below 0° C for the air temperature during a given time period.

an extensive body of the atmosphere in which physical properties, particularly temperature and humidity, exhibit only small and continuous differences in the horizontal plane; it may extend over an area of several million square kilometers and over a height of several kilometers.

the ambient temperature indicated by a thermometer exposed to the air but sheltered from direct solar radiation, or placed in an instrument shelter 1.5 to two meters above ground; also called surface temperature.

the cumulative number of degree-days above 0°C for the air temperature during a given period.

a large depression of the ground surface produced by thawing of a large area of very thick and exceedingly ice-rich permafrost.

a non-dimensional, unitless quantity that measures how well a surface reflects solar energy; ranges from 0 - 1; a value of 0 means the surface is a “perfect absorber,” where all incoming energy is absorbed, a value of 1 means the surface is a “perfect reflector,” where all incoming energy is reflected and none is absorbed.

a low centered on the eastern slope of the Canadian Rockies in the province of Alberta, Canada.

the low pressure center located near the Aleutian Islands on mean charts of sea level pressure during the winter; it represents one of the main centers of action in the atmospheric circulation of the northern hemisphere.

refers to high mountain areas above the timber line (where trees cease to inhabit extremely cold environments).

a glacier that is confined by surrounding mountain terrain; also called a mountain glacier.

annual accumulations of snow and dust on a glacier.

the lowest altitude at which mountain permafrost occurs in a given highland area outside the general permafrost region.

the vertical subdivision of an area of mountain permafrost into permafrost zones, based on the proportion of the ground that is perennially cryotic.

a principal middle level cloud type (cloud genus), white or gray, or both white and gray, which occurs as a layer or patch with a wave aspect, the elements of which appear as laminae, rounded masses, rolls, etc; these elements usually are sharply outlined, but they may become partly fibrous or diffuse; they may or may not be merged, and they generally have shadowed parts; most of the regularly arranged altocumulus elements have an apparent width of 1 - 5 degrees.

a principal middle level cloud type (cloud genus) in the form of a grayish (gray) or bluish cloud sheet or layer of striated, fibrous, or uniform appearance, totally or partly covering the sky; the layer has parts thin enough to reveal the position of the sun; halo phenomena do not usually occur.

any wind blowing up a steep incline or mountain; the opposite of katabatic wind.

in synoptic meteorology, a detailed study of the state of the atmosphere over a particular region based on the actual observations.

submerged ice which is attached to the bottom.

an instrument which measures wind speed or wind speed and direction; a cup anemometer measures the wind speed from the speed of rotation of a windmill which consist of 3 or 4 hemispherical or conical cups, each fixed to the ends of horizontal arms attached to a vertical axis; a byram anemometer is a variety of the cup anemometer; a counting anemometer has cups or a fan whose rotation is transmitted to a technical counter which integrates directly the air movement speed; a hand anemometer is small portable anemometer held at arm's length by an observer making a wind speed measurement; a pressure tube anemometer (dines anemometer) is an instrument which derives wind speed from measurements of the dynamic wind pressures - wind blowing into a tube develops a pressure greater than the static pressure, while wind blowing across a tube develops a pressure less than the static, this pressure difference is proportional to the square of the wind speed.

a Russian anemograph (recording anemometer) which is equipped with a device to record the wind direction in addition to wind speed.

a Russian anemometer combined with a vane to determine the wind direction.

an instrument for measuring atmospheric pressure; it is constructed on the following principles: an aneroid capsule (vidie capsule, which is a thin, disk-shaped box or capsule, usually metallic) is partially evacuated of gas, and is restrained from collapsing by an external or internal spring; the deflection of the spring will be nearly proportional to the difference between the internal and external pressures; magnification of the spring deflection is obtained both by connecting capsules in series and by mechanical linkages.

deviation of a meteorological quantity value in a given region from the normal (mean) value for the same period.

the line of latitude 66° 34′ S (often taken as 66.5° S); along this line the sun does not set on the day of the summer solstice, and does not rise on the day of the winter solstice.

also known as the antarctic convergence; the southern front of the antarctic circumpolar current that separates the antarctic zone in the south from the polar frontal zone in the north; taken by many to delineate the actual northern boundary of the antarctic zone; characterized by sea surface temperatures near 5°–6° C and a salinity minimum of 33.8–34.0 psu produced by high rainfall.

the region between the antarctic circle (66° 34′ S) and the South Pole; climatically, the limit of the zone may be set at about 60° S, poleward of which the prevailing westerly winds give place to easterly or variable winds; over most of this region the average temperature does not rise above 0°C (32°F) even in summer.

the prevention of ice accumulation of aircraft, ships and other objects; the most common measures are heating or applying a dressing by brush or spray to weaken adhesion and facilitate removal.

an ice wedge that grows progressively downwards into a receding slope, in a direction normal (perpendicular) to the surface.

area of increased atmospheric pressure relative to surrounding pressure field in the atmosphere; it is outlined by closed isobars on a synoptic surface chart, and by closed contours on a constant-pressure chart; this term is used interchangeably with high.

area of increased atmospheric pressure relative to surrounding pressure field in the atmosphere; outlined by closed isobars on a synoptic surface chart, and by closed contours on a constant-pressure chart; used interchangeably with high..

system of air movements (atmospheric circulation) associated with an anticyclone, which is clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere.

the amount of heat required to raise the temperature of a unit mass of frozen ground by one degree.

the cumulative number of degree-days below 0 degrees Celsius for a given time period, calculated from the mean monthly temperatures for a specific station without making corrections for positive degree-days in spring and fall.

the cumulative number of degree-days above 0 degrees Celsius for a given time period, calculated from the mean monthly temperatures for a specific station without making corrections for negative degree-days in spring and fall.

(from Greek arktikos which means northern) northern polar region of the earth which includes almost the whole area of the Arctic Ocean and adjacent areas of Eurasian and North American continents.

mass of very cold air in the arctic regions which invades lower latitudes at irregular intervals.

the line of latitude 66 degrees 34 minutes N (often taken as 66.5 degrees N); along this line, the sun does not set on the day of the summer solstice, and does not rise on the day of the winter solstice.

(1) the semi-permanent, semi-continuous front between the deep, cold arctic air and the shallower, basically less cold polar air of northern latitudes (2) south boundary of the arctic air mass.

haze in arctic regions which reduces horizontal and slant visibility and which may extend to a height of about 10 km; it appears blue-grey when viewed away from the sun, and reddish-brown toward it.

a weak high which appears over the arctic basin during late spring, summer and early autumn; one of the centers of action in the atmosphere.

a mist of ice crystals; a very light ice fog.

an atmospheric circulation pattern in which the atmospheric pressure over the polar regions varies in opposition with that over middle latitudes (about 45 degrees N) on time scales ranging from weeks to decades; the oscillation extends through the depth of the troposphere, and from January to March, it extends upward into the stratosphere where it modulates in the strength of the westerly vortex that encircles the arctic polar cap region; the north atlantic oscillation and arctic oscillation are different ways of describing the same phenomenon.

evaporation (steam) fog produced above a surface of open water within arctic ice when the air is stable and relatively cold.

the northern limit of tree growth; the sinuous boundary between tundra and boreal forest; taken by many to delineate the actual southern boundary of the arctic zone.

(1) geographically, the area north of the arctic circle (66° 34′ N) (2) (same as tundra) biogeographically, the area extending northward from the arctic tree line; also used for the level above the timber line in mountains.

sharp, narrow ridge formed as a result of glacial erosion from both sides.

the process of inducing or maintaining a frozen condition in earth materials by artificial means.

the envelope of air surrounding the earth and bound to it more or less permanently by virtue of the earth's gravitational attraction; the system whose chemical properties, dynamic motions, and physical processes constitute the subject matter of meteorology.

the large-scale movement of air, and the means by which heat is distributed on the surface of the Earth; may vary from year to year.

as commonly used in weather observing practice, an observable occurrence of particular physical significance within the atmosphere; from the viewpoint of weather observations, the atmospheric phenomena include all hydrometeors (precipitation types and fogs), blowing snow, thunderstorms, tornadoes, waterspouts, and others.

pressure (force per unit area) exerted by the atmosphere on any surface by virtue of its weight; it is equivalent to the weight of a vertical column of air extending above a surface of unit area to the outer limit of the atmosphere.

longwave (infrared) radiation emitted by or being propagated through the atmosphere.

luminous phenomena, in the form of arcs, bands, draperies, or curtains in the high atmosphere over high latitudes; auroras are related to magnetic storms and the influx of charged particles from the sun, the phenomena are called aurora borealis in the northern hemisphere and aurora australis in the southern hemisphere.

mass of snow which becomes detached and slides down a slope, often acquiring great bulk by fresh addition as it descends.

arithmetic mean (m) of a number (n) of values (x1, x2, ... xn), defined by the equation: m = sxi/n; annual average value is calculated from 12 monthly means; daily average (or mean) value is calculated from 24 hourly readings of a meteorological element, or often from the average of the daily maximum and minimum values (for example, of temperature); monthly average is usually calculated as the average of the daily average values.

the semipermanent subtropical high over the North Atlantic Ocean, especially when it is located over the eastern part of the ocean; the same high over the western part of the Atlantic is called the Bermuda high; on mean charts of sea level pressure, this high is one of the primary centers of action in northern latitudes.

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