wind chill

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wind chill,

the cooling effect of wind and temperature combined, expressed in terms of the effect produced by a lower, windless temperature, also called wind chill factor, wind chill temperature, wind chill equivalent temperature, wind chill index, wind chill equivalent index, and wind chill temperature index. Wind chill is based on the rate of heat loss from exposed skin. Under windless conditions air provides an invisible blanket around the skin. As wind speed increases, this layer of heated air is carried away from the body at an accelerated rate, forcing the body either to work harder to generate more heat or cool down. If the actual air temperature is −5°F;(−21°C;) with a 20 mph (32 km/hr) wind, the wind chill temperature is −29°F;(−34°C;). Because wind chill is based the removal of heat from the human body, it does not reflect the increased rate of heat loss for inanimate objects such as automobile radiators under the same conditions but they also experience a faster heat loss with increasing winds.

The term wind chill was coined by the American geographer Paul A. Siple in his dissertation, Adaptation of the Explorer to the Climate of Antarctica, (1939). Subsequently, on the third Byrd Antarctic expedition, Siple and American geologist Charles Passel determined how quickly extreme conditions could produce frostbite on exposed skin. By 1945, Siple and Passel had published a set of numbers expressing heat loss as a function of temperature and wind speed.

A wind chill advisory is issued when the forecast projects a wind velocity of at least 10 mph (16 km/hr) producing a wind chill temperature of −15°F; or lower for 3 hours or more. At these values wind chill is more of a nuisance than it is life threatening. A wind chill warning is issued when the forecasted wind chill temperature is −25°F; or lower, which can be life threatening if the individual is not suitably dressed. Persons who go outside under such conditions may experience frostbite and other cold-related symptoms in a matter of minutes, even if properly clothed for normal winter conditions, and longer exposures may prove fatal.

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wind chill

[′win ‚chil]
(meteorology)
That part of the total cooling of a body caused by air motion.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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Wind chill index has wide range of applications in countries located in cold regions, in a way that an opinion poll performed in Canada shows that 82% of the people of this country use wind chill index in order to plan their daily outdoor activities in winter.
Wind chill index as a regional index affecting human's comfort.
Copies of the new gentler, warmer wind chill index chart (complete with the new frostbite exposure time guide) and a chart comparing the old and new wind chill temperatures for various wind speeds on a 5-degree day accompany this article.