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Unformatted text preview: Chapter 4- Water enters the atmosphere through evaporation, which is greatest when it is warmer, winds are high, and atmospheric pressure is low.- Saturation occurs when the rate of molecules condensing is equal to the number of molecules leaving the liquid (rate of return is equal to rate of escape).- Measuring water vapor is important because water vapor is the source of all clouds and precipitation and it is the most important greenhouse gas.- Mixing ratio is one to express the amount of water vapor in the atmosphere. It is the ratio of the weight of water vapor to the weight of the other molecules in a given volume of air.- Vapor pressure is the pressure exerted by water vapor molecules. Increases with increasing temperature. - Similarly, when air is saturated, the pressure exerted by water vapor molecules is called Saturation Vapor Pressure. - Saturation Vapor Pressure increases rapidly as temperature increases because the speed of the molecules is increased and the number of molecules with enough kinetic energy to evaporate also increases.- Relative humidity indicates how closely the air is to being saturated and is the ratio of vapor pressure to the saturation vapor pressure multiplied by 100%.- Saturated air has a relative humidity of 100%.- Water evaporates more slowly in air with a high relative humidity, and more quickly in air with a low relative humidity.- Adding water vapor or cooling the air, or both, increases relative humidity, while removing water vapor, warming the air, or both decrease relative humidity.- Dew occurs when relative humidity is beyond 100% (point when air cannot contain any more moisture) and the excess moisture must condense out of the air until the humidity returns to 100%....
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This note was uploaded on 01/30/2012 for the course AOSC 200 taught by Professor Hudson during the Fall '08 term at Maryland.
- Fall '08