1. Cloud Formation

2. Air Pressure Caused by the weight of the air above it
Decreases with elevation
Barometric pressure
Barometer
Millibars / mm Hg

3. Pressure and Temperature
When pressure drops air expands and cools

4. Cloud Formation Air rises Air expands Dew point is reached
decrease in pressure
Air expands
Temperature decreases
Dew point is reached
Water vapor condenses on tiny particles (condensation nuclei)

5. Processes That Lift Air
Mountains

6. windward leeward

7. Processes That Lift Air
Fronts
Boundary between two different air masses
Warm air is forced up by more dense cold air

8. Source region – area where air masses originate

9. Processes That Lift Air
Convergence