Global and Local Winds i

What causes wind? 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, winds form.

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.

There are 2 types of winds… 1. Local Winds 2. Global Winds

Don’t travel North and South because of the Earth rotating on its axis. 4 Types of Global Winds – Doldrums – Trade Winds – Prevailing Westerlies – Polar Easterlies Global Winds

Visual of Global Winds

Doldrums These are located at the equator, surface winds are calm and weak. Why are they called doldrums? Sailors found that there were no winds near the equator for a period of time. The ships were essentially stuck in one place, not being able to move forward. These calm periods were called doldrums. Today, to be “stuck in the doldrums” means that you’d like to be doing something, but you’re stuck waiting for something to happen so you can begin moving forward.

Named from their ability to quickly propel trading ships across the ocean - found between about 30° latitude and the equator - steady and blow about 11 to 13 mph - In the Northern Hemisphere, the trade winds blow from the northeast and are known as the Northeast Trade Winds - In the Southern Hemisphere, the winds blow from the southeast and are called the Southeast Trade Winds. Trade Winds

Prevailing Westerlies Strong winds Located in the belt from degrees latitude in both hemispheres. Has an impact on the US weather

Cold, but weak winds Near the north and south poles US weather is influenced by these Cooling takes place between the degree latitude as it approaches the poles Polar Easterlies

Jet Stream High altitude winds found in the upper troposphere/lower stratosphere Ribbon of strong high speed 50 mph to 300 mph Moves west to east around the Earth separating cold air from warm. Pilots travel with the jet stream to save fuel and travel faster  Weather forecaster use the jet stream to locate and forecast frontal system movement.

What brings certain weather phenomenon? El NinoLa Nina occurs when the surface temperature rises above the normal water temperature in the Equatorial Pacific Ocean creating more humidity in the atmosphere Known to increase number of hurricanes Occur more frequently (every 3- 7 years)  occurs when the surface temperature falls below the normal water temperature in the Equatorial Pacific Ocean creating a more dry atmosphere  Known to create drought conditions

Local Winds Cover short distances Blow from any direction 2 Types of Local Winds – Sea Breezes- from sea to land – Land Breezes – from land to sea -Mountain Breezes cool air sinks to valley -Valley Breezes warm air rises up slope

What’s the difference?

How do sea and land breezes work?

Valley and Mountain Breezes