1. Understanding Air Pressure
also called atmospheric pressure or barometric pressure

2. Air Pressure
results from the weight of a column of air extending from the top of the thermosphere to the surface
About 1 kg/cm² or 14.7 lbs/in²

3. Just like this aquarium example
If air pressure was only exerted downward that would squish us!!!
But air pressure is exerted in all directions
Just like this aquarium example

4. Measuring Air Pressure
A barometer is an instrument used to measure atmospheric pressure
When air pressure increases, the mercury in the tube rises

5. What the barometer tells you
When the barometer falls, a low pressure system is moving in. This means cloudy weather (rain).
When the barometer rises, a higher pressure system is moving in. Clear weather.

6. Air flows from areas of higher pressure to areas of lower pressure
What is WIND?
Wind is the result of horizontal differences in air pressure
High Pressure
Low Pressure
Air flows from areas of higher pressure to areas of lower pressure

7. Why do air pressures vary?
The unequal heating of Earth’s surface generates pressure differences
Therefore…
Solar radiation is the ultimate energy source for most wind