Wind Chill Atmospheric Sciences 101 Autumn 2020 Weather

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Wind Chill Atmospheric Sciences 101 Autumn 2020

Wind Chill Atmospheric Sciences 101 Autumn 2020

Weather Channel

Weather Channel

Wind Chill • Is a measure how cold you FEEL, considering the effects of

Wind Chill • Is a measure how cold you FEEL, considering the effects of winds. • There a lot of misconceptions. For example, if the temperature is 35 F and the wind chill is 29 F, will water freeze?

NO!

NO!

Wind Chill The first wind chill formulas and tables were developed by Paul Siple

Wind Chill The first wind chill formulas and tables were developed by Paul Siple and Charles Passel working in the Antarctic before the Second World War, and wind chill info was first made available by the National Weather Service in the 1970 s.

Wind Chill Was Based on Experiments Measured cooling rates of bottles of water for

Wind Chill Was Based on Experiments Measured cooling rates of bottles of water for various combinations of temperature and wind

Cooling rate depends on two things • Difference in temperature between bottle (or skin)

Cooling rate depends on two things • Difference in temperature between bottle (or skin) and the environmental air • Wind speed, which controls how quickly cold air is mixed down to the bottle/skin, and how rapidly warm air near bottle/skin is removed.

Led to Wind Chill Formula Estimating Loss of Heat as a Function of Temperature

Led to Wind Chill Formula Estimating Loss of Heat as a Function of Temperature and Wind Speed

Wind Chill Temperature • Definition: a still-air temperature that would have the same cooling

Wind Chill Temperature • Definition: a still-air temperature that would have the same cooling effect on exposed human skin as a given combination of temperature and wind speed • Also called wind chill index and wind chill equivalent temperature

Formula Updated in 2001 Comparison of old and new wind chill values at −

Formula Updated in 2001 Comparison of old and new wind chill values at − 15 C (5 F)

Will water freeze with a temperate of 35 F and a wind chill of

Will water freeze with a temperate of 35 F and a wind chill of 30 F?

Can Hell Freeze Over?

Can Hell Freeze Over?

Yes

Yes

Wind Chill and Safety

Wind Chill and Safety

Frostbite Can Occur Rapidly at Low Windchills

Frostbite Can Occur Rapidly at Low Windchills

Why goosebumps when cold?

Why goosebumps when cold?

Cold air makes hairs stick up to slow air and help create an insolating

Cold air makes hairs stick up to slow air and help create an insolating dead-air layer