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The Temperature of Wind.

  1. May 22, 2013 #1
    This may be a ridiculous question, or we may be overlooking what is a simple answer but a friend and I can't come to a reasonable conclusion.

    Why does a strong wind feel colder then a gentle breeze?

    We have thought about the fact that this may not be the case at all and that the temperature of the "wind" is independent of speed. Although, in my experience, strong winds are perceived as being colder then no wind.

    I live in a fairly mild climate (average temperature of around 13 Celsius), and have thought that possibly hot climates, where air temperature exceeds that of our skin temperature, that an increase in wind speed may cause it to be perceived as hotter?

    If anybody can offer an explanation, or confute everything I have said, it would be greatly appreciated.

    Cheers.
     
  2. jcsd
  3. May 22, 2013 #2
    Having just submit this question, I have come to realise that the air will be conducting heat from my body. Hence, strong winds would not allow the air immediately next to my skin to rise in temperature a meaningful amount.

    Thoughts on this?
     
  4. May 22, 2013 #3
    Yea, I think that is right. Maybe more importantly than the temperature surrounding your skin is the humidity surrounding your skin. Water evaporates off of your skin, cooling it and raising the humidity of the air near by. With higher humidity evaporation is harder. A wind blows that humidity away and evaporation can proceed easily again.
     
  5. May 22, 2013 #4
    It's essentially the same idea as evaporative cooling - the moving air absorbs some small amount of heat from your skin, but before everything has time to equilibrate the air molecules "blow" away, and whatever small gain in energy they received is lost by your skin.
     
  6. May 22, 2013 #5
    This had been bugging us for a while. Don't know why we couldn't think of this ourselves.

    Thanks for the help.
     
  7. May 22, 2013 #6
    That's a good point too. Come to think of it at higher temperatures that's probably the dominant effect.
     
  8. May 22, 2013 #7
    Note that temperature of the wind is independent of speed. Temperature is a function of the internal movement of air molecules, not the external speed of a pocket of air. A thermometer which does not have a metabolism or water to evaporate will read the same temperate for still air as it will for moving air. (a further caveat would be that the friction and compression created by a thermometer in a very intense airstream could heat up the thermometer)
     
  9. May 23, 2013 #8

    QuantumPion

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    The reason why wind feels cold even though the actual air temperature is the same is because of convective heat transfer. The moving air transfers heat away from your body faster than stagnate air, so it feels colder. Similar to the reasoning why a metal pole feels colder to the touch than a wooden pole, even though they are the same temperature.
     
  10. May 23, 2013 #9
    That doesn't explain why. All you've said is "cold wind feels cold because it removes heat". The actual explanation is partly what I wrote and mostly what Modus wrote I believe.
     
  11. May 23, 2013 #10

    QuantumPion

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    That is not what I said. What I said was moving air feels colder than still air because it removes heat more quickly. Evaporative cooling is a separate effect. If you wore a thin wetsuit which was not a good thermal insulator but blocked all moisture, you would still feel colder in wind than in still air.

    This is correct, however note that a thermometer that starts at indoor room temperature and brought outside will reach equilibrium with outside environmental temperature faster if it is exposed to wind than if it was exposed to still air.

    What we perceive as temperature is the rate of heat transfer, not absolute temperature.
     
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