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Name: Chris
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Question:
If it is 2oC outside (air temp) but the wind chill feels like -5oC, can a puddle of water freeze?


Replies:
Chris,

The wind chill is a measure of the apparent temperature that your skin feels as air blows over it and cools your skin temperature. Wind can help reduce the temperature of water by taking energy away from it (by evaporation or by removal of heat) but it cannot cool the water to much below the air temperature. Therefore, in the situation that you have suggested, the water will not freeze.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory


I do not know about those particular numbers, but it IS possible for water to freeze at a temperature just slightly above 0 C, if it is open so that some of it can evaporate. Evaporation of just a little water takes enough thermal energy away from the remaining water that its temperature can drop below the temperature of the surroundings.

Yes, freezing, on the other hand, releases heat energy, but that is a much smaller effect than the energy loss by evaporation.

Richard Barrans


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