Download Wind - Earth Science with Mrs. Cox

Air Pressure and Wind
Chapter 19
Air Pressure
- weight of air pushing in all directions
- barometer- device that measures air pressure
ex.- air pressure rises = mercury rises
air pressure falls = mercury falls
Wind
- caused by:
1) Unequal heating of air
creates pressure
differences.
2) Pressure differences
move air from high areas
to low areas.
Factors Affecting Wind
1) Pressure Difference
- greater difference causes stronger wind
2) Coriolis Effect
- Earth’s rotation deflects winds:
a) to the right in the Northern Hemisphere
b) to the left in the Southern Hemisphere
3) Friction
- Earth’s surface can slow wind down
Coriolis Effect
Wind on a Weather Map
Isosbars- lines that show air pressure
1) close lines = large pressure differences
2) widely space lines = small pressure differences
Pressure Centers
High Pressure
- winds blow outward (air sinks, pushing out)
- winds move clockwise
- pressure is high in the center
- creates clear weather
Low Pressure
- winds blow inward (air rises, pulling in)
- winds move counterclockwise
- pressure is low in the center
- creates clouds, bad weather
Global Winds
- warm air moves toward the poles
- cold air moves toward the equator
Examples of Global Winds:
1) Trade Winds - blow east to west at equator
2) Westerlies
- blow west to east above trade winds
* IN U.S.- weather is affected most by westerlies
3) Polar Easterlies
- polar wind that moves east to west
Local Winds
- caused by land and water heating
1) Land Breeze
- at night, land cools moving air away from land.
2) Sea Breeze
- during day, land heats moving air to the land.
3) Mountain Breeze
- at night, air cools & moves down the
mountain into the valley
4) Valley Breeze
- during day, air heats & moves up the
mountain out of the valley
Anemometer
- device that measures wind speed.
El Nino
- The heating of cold ocean water in the East
Pacific Ocean.
- caused by ocean currents going in reverse
- affects weather & fishing
La Nina
- The cooling of ocean water in the East
Pacific Ocean.
- also affects weather