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Unformatted text preview: time in the air is dependent on air temperature. A ratio of the amount of water vapor in the air, relative to how much water vapor that air can hold. Expressed as a percentage If the air holds half the moisture possible at the present temperature, the RH is 50%. When the humidity is 100%, the air holds the maximum amount possible. When air is cooled, the capacity is reduced and has a higher percentage of total capacity. Relative humidity
Actual water vapor content of the air Maximum water vapor capacity of the air at that temperature Relative humidity = X 100 As air temperature rises relative humidity drops Daily relative humidity patterns Therefore RH tends to be highest first thing in the morning when temperatures are lowest What do you notice about the relationship between temperature and relative humidity?
With no change in water vapor content: An increase in air temperature lowers the RH A decrease in air temperature raises the RH Measuring humidity Hair Hygrometer Psychrometer Air saturation = 100% relative humidity; that is the air is holding as much moisture as it can at its particular temperature = the dew point Dew Point = Temperature at which air with a given humidity will reach saturation when cooled If the air temperature and the dew point temperature are the same = 100% humidity. Further saturation will result in the formation of clouds, fog, etc. due to active condensation Moist air has a...
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- Spring '10