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.
a line of latitude at approximately 66 degrees 33 minutes N (66°33’ N) that marks the border of the Arctic, the northernmost region of Earth. 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.