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Unformatted text preview: saturate it. As the shower continues, there is no more room for water vapor, so
condensation increases and you fog up the mirror. If you have a cold glass of ice
tea on a humid day, the air next to the glass is chilled, which may bring it to
saturation. Then condensation occurs and water drops form on the outside of the
glass. So, we are causing condensation by saturating the air–in the bathroom by
adding moisture to the air and with the drink by cooling the air next to the glass.
We’ll spend a fair amount of time looking at how nature does these same things
and the resulting clouds and precipitation. Atmospheric Moisture:3
Cooling the Air
Nature has several ways of cooling the air and causing saturation and
condensation. One is to remove energy from the air in what we call diabatic
processes. Dew is like the water on our glass in that the air near the surface is
cooled to the dew point, generally at night. Dew will not form on windy nights
because the air is mixed up and no air is in contact with the surface long enough
for the condensation to occur. If the dew point is below freezing, then frost will
appear, instead of dew. Fog is essentially a cloud found at the ground surface.
Diabatic processes cause most fog. Radiation fog, for example, appears when
the air at night gives off enough longwave radiation to cool to the dew point.
Advection fog occurs when warm, moist air moves over a cooler surface. This
is common in coastal areas where warmer, moister air over the water moves over
the land during the night.
Clouds generally form not by the removal of energy, but by changing the v...
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This document was uploaded on 10/27/2011 for the course GEOG 1401 at Texas Tech.
- Fall '08