permafrost

1. (Also called perennially frozen ground, pergelisol, permanently frozen ground.) A layer of soil or bedrock at a variable depth beneath the surface of the earth in which the temperature has been below freezing continuously from a few to several thousands of years.

Permafrost exists where the summer heating fails to descend to the base of the layer of frozen ground. A continuous stratum of permafrost is found where the annual mean temperature is below about -5°C (23°F).
Compare pereletok;
see active layer.

1. As limited in application by P. F. Svetsov, soil that is known to have been frozen for at least a century.
   Muller, S. W. 1947. Permafrost, or Permanently Frozen Ground, and Related Engineering Problems.
   Hare, F. K. 1951. Compendium of Meteorology. p. 958, and map, p. 956.

1. (Also called perennially frozen ground, pergelisol, permanently frozen ground.) A layer of soil or bedrock at a variable depth beneath the surface of the earth in which the temperature has been below freezing continuously from a few to several thousands of years.

1. The study of the physics, chemistry, and dynamics of the earth's atmosphere, including the related effects at the air–earth boundary over both land and the oceans. Fundamental topics include the composition, structure, and motion of the atmosphere. The goals ascribed to meteorology are the complete understanding and accurate prediction of atmospheric phenomena.