Why does warm air hold more water than cold air?

Factual Questions
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I have a fair grasp of adiabatic cooling rates (both wet and dry), the hydrogen bond, phase changes, and a few other concepts along the same lines. I (somewhat) understand the physical mechanisms that give rise to these properties. But I recently realized that I never really understood the concept that warm air can hold more water than cold air. Why is this true? Is it because warm air has more energy, so groups of water molecules can’t maintain bonds between themselves for very long? I.e. is it akin to the reasons why ice, liquid and vapor form at different temperatures? But wouldn’t a somewhat turbulent cold air mass have enough energy to keep this from happening, leading to a moist, cold wind? Does it have anything to do with the relative volumes of an air mass at varying temperatures. That is, a parcel of air at one temperature takes up a lot more room when you add heat. With the increased volume the parcel takes up, more H[sub]2[/sub]O can fit and still be far apart from each other to avoid bonding, condensing, and falling on my parade. Any thoughts?

Thanks,

Rhythmdvl

2

No no no!

Air does not “hold” water. Air is just a mixture of gases that all have their own properties. It just so happens that we notice water’s phase changes because they happen at normal climatic temperatures.

Water vapor is constantly condensing and evaporating (as is every other atmospheric gas). At colder temperatures, the condensation rate exceeds the evaporation rate, and there is a net gain in liquid water evident (in the form of clouds, fog, dew, frost).

If the air gets cold enough, even oxygen and nitrogen will form dew. (But that’s pretty fargin’ cold!)

3

P.S. - Here’s a better explanation at the Bad Meteorology web site, which is associated with fellow SDMBer Bad Astronomer’s Bad Astronomy site.