Winds Cause of Wind

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

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,

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.

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

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.

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

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

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.

Prevailing Westerlies • Strong winds • Located in the belt from 30-60 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

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

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

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

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

http://www.youtube.com/watch?v=gM0d3fGew-0&feature=player_detailpage