Why does water vapor rise from ponds on cold mornings?

I know it has to do with temperature differences, the pond water being hotter than the ambient air. But surely the water molecules are not heated enough to vaporize and become steam?

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  • 1 decade ago
    Best Answer

    At normal surface atmospheric pressure, water evaporates. Even ice cubes in a freezer will evaporate. The vapor is not hot enough to be steam, as from a kettle or heated pot, but it is water vapor, and the lower air temperature cause the vapor to condense enough to be visible.

  • it's the same reason that your breath becomes cloudy when it's cold. I don't know how much you know, so I'll walk you through it.

    Water evaporates faster when it's warmer, and warm air can hold more water vapor than colder air. So, the pond is heated up because the sunlight goes straight through the air (without being absorbed), but when it hits the water, it is absorbed, and transfers its energy into heat. This raises the water temp, making more water want to evaporate.

    When that water evaporates, however, the air is still cold, and that water then cools down and is no longer stable as a gas. Since it no longer wants to be a gas, it returns to a liquid form, combining with other like-minded molecules to form little droplets in the air, which make the mist.

    Any time you see "steam" coming off something, this is essentially what's happening. If you hold a popsicle up on a hot day, you'll see steam around it, because it's cooling down the air around it, and water that was ok in the hot summer air suddenly cools down as it gets close to the popsicle, and drops out.

    This is also why condensation forms on the outside of a glass of ice water.

  • 1 decade ago

    To the excellent answers you have already received I will add only this: What you see over the pond is fog. Not much of it but it the pond was the ocean, it would be real fog. It only occurs when air doesn't rise up and that happens only when there is an inversion, i.e. warmer air on top of colder air.

    The reason it happens often in the first hour of the morning is that, if there are no clouds, during the night, heat from the ground radiates to ... space! As the layer of air near the ground cools down, it creates an inversion. Note that there mustn't be much wind because wind will tend to mix again the air masses near the ground.

  • 1 decade ago

    Water vapor rises off of the pond all the time. The fact is, you only see it when it is cold because it hits the cold air. You breath all the time, yet you only see your breath when it is cold.

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  • 1 decade ago

    water vapors come off from all water bodies, the only time you see it is when the air temperature is colder than the water or water vapor, this produces fog also, much as you can see your breath in cold air temps.

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