1. Winds
Cause of Wind

2. How Wind Develops
Caused by a difference in air pressure due to
unequal heating of the atmosphere

3. Winds are created by….
• Heating the air, decreases pressure (warm air rises creating a low pressure)
• Cool air rushes into replace the warm air
(cooler dense air, produces high pressure)
• As air goes from high to low pressure,

4. Coriolis Effect
• Coriolis Effect – Rotation of
the Earth causes moving air
and water to change directions
• Northern Hemisphere winds
curve to the right
• Southern Hemisphere winds
curve to the left.

5. 3 Types of Winds
1.Planetary or prevailing wind.
2.Periodic winds
3.Local winds

6. Planetary Winds : The winds blowing throughout the year from one latitude to another in response to latitudinal differences in air pressure are called planetary or prevailing winds.
Trade winds, Westerlies and Polar winds are planetary winds.

8. Doldrums
At the equator, surface winds are calm and weak.

10. Trade Winds
• 30 degrees N & S of Equator
• Calm winds, few clouds, little rain fall
• Warm air rising from Equator cools and
sinks
• Also known as Horse Latitudes

11. Horse Latitudes or Subtropical High are subtropical latitudes between 30 and 35 degrees both north and south. This region, under a ridge of high pressure called the subtropical high, is an area which receives little precipitation and has variable winds mixed with calm.

12. Prevailing Westerlies
• Strong winds
• Located in the belt from degrees
latitude in both hemispheres.
The Roaring Forties is the name given to strong westerly winds found in the Southern Hemisphere, generally between the latitudes of 40 and 50

13. Similar but stronger conditions occur in more southerly latitudes, and are referred to as the Furious Fifties and Shriekingor Screaming Sixties.

14. Polar Easterlies
• Cold, but weak winds Near the north and south poles
• Cooling takes place between the 50-60
degree latitude as it approaches the poles

15. Periodic Winds : Periodic winds change their direction periodically with the change in season, e.g. Monsoons, Land and Sea Breeze etc.

17. Local Wind : Local winds develop as a result of local differences in temperature and pressure. chinook is an example of local winds.