2What causes wind? Caused by a difference in air pressure due to unequal heating of the atmosphere.
3Winds 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.
4Coriolis 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.
5There are 2 types of winds… 1. Local Winds2. Global Winds
6Global 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
8These are located at the equator, surface winds are calm and weak. DoldrumsThese 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.
9Trade WindsNamed 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.
10Prevailing Westerlies • Strong winds• Located in the belt from degrees latitude in both hemispheres.• Has an impact on the US weather
11Polar Easterlies• 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
12Jet Stream • Discovered in 1940’s • Can be found in the upper troposphere• Strong high speed and high pressure• Moves west to east across the US, movingstorms
13What brings certain weather phenomenon? El NinoLa Ninaoccurs when the surface temperature rises above the normal water temperature in the Equatorial Pacific Ocean creating more humidity in the atmosphereKnown to increase number of hurricanesOccur 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 atmosphereKnown to create drought conditions
14Local 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