1. Humidity

2. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Humidity Humidity : the amount of water vapor in the air The maximum quantity of moisture that can be held in the air depends on air temperature

3. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Humidity Relative Humidity : compares the amount of water vapor present in the air to the maximum amount that the air can hold at that temperature Expressed as a percentage: At 100% relative humidity, air is saturated.

6. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. Dew-point temperature : temperature at which air with a given humidity will reach saturation when cooled without changing its pressure Humidity

8. Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc. The Adiabatic Process As a parcel of air rises  pressure on the parcel decreases  air expands and cools As a parcel of air descends  pressure on the parcel increases  air is compressed and warms Atmospheric pressure decreases with altitude so...