SOME INSTANCES OF UNSTABLE SURFACE TEMPERATURE CONDITIONS DURING AN ARCTIC WINTER*
A TMOSPHERIC conditions in which the air has a vertical temperature strati- fication such that portions tend to rise and become turbulent, are frequently observed in temperate climates. These turbulent conditions, in which the atmosphere is said to have an unstable or superadiabatic temperature grad...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.539.3007 http://pubs.aina.ucalgary.ca/arctic/Arctic8-3-148.pdf |
| Summary: | A TMOSPHERIC conditions in which the air has a vertical temperature strati- fication such that portions tend to rise and become turbulent, are frequently observed in temperate climates. These turbulent conditions, in which the atmosphere is said to have an unstable or superadiabatic temperature gradient are commonly caused by solar heating of the earth's surface and the transfer of some of the earth's heat to ' the atmosphere. Such conditions produce the vertical transport of moisture evidenced by cumulus clouds. Although the Arctic is generally characterized by a stable or quiescent atmospheric structure, unstable conditions1 as shown by superadiabatic temperature gradients do occur. They were recorded during a field obser-vational program a t Eielson Air Force Base, near Fairbanks, Alaska. The fact that these conditions were observed in winter when the sun was at a very low angle above the horizon, and even on overcast days, led to a more detailed examination of the data to explain the cause of these phenomena. Although these turbulent or superadiabatic situations are much less frequent during the arctic winter than are inversions or stable conditions, they appear to be important in some arctic weather situations, of which ice fog is one example. Data on the occurrence of unstable surface temperature gradients will thus aid the description of various aspects of the weather in the Arctic and will show some of the complexities of northern weather. Superadiabatic lapse rates were observed under several different general weather conditions. One, as might be expected, was during periods of strong insolation when the snow surface was in bright sun. Although the sun is quite low during much of the winter in the Fairbanks area, surface heating at about noon begins to be significant after the middle of February. Another condition which was observed to cause a superadiabatic situation was one in which a heavy overcast and an overriding air mass considerably warmer than "This study represents a portion of a project ... |
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