The portion of the cooling of a human body caused by air motion. Air motion accelerates the rate of heat transfer from a human body to the surrounding atmosphere, especially when temperatures are belo
w about 7C (45F).
A means of quantifying the threat of rapid cooling during breezy or windy conditions that may result in hypothermia in cold conditions. The index is used to remind the public to minimize exposure when
outdoors and to take precautionary actions. In the late 1940s, Antarctic explorers Siple and Passel experimented with measuring the time it took to freeze 250 grams of water in different temperature and wind conditions. They developed empirical formulas relating these data to the rate of heat loss from exposed human skin. They developed the following formula which was used to determine the wind-chill index. At wind speeds of 4 mph or less, the wind chill temperature is the same as the actual air temperature: T_WC = 0.0817(3.71V^0.5 + 5.81 - 0.25V)(T-91.4)+91.4 where V is wind speed in mph and T is temperature in F.
A type of snow crust formed by the packing action of wind on previously deposited snow. Wind crust may break locally, but, unlike wind slab, does not constitute an avalanche hazard.