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. http://www.youtube.com/watch?v=mcPs_OdQOYU Do Now – In Binders Describe how wind is created. What is the relationship between density and pressure? What happens to air pressure as I hike up a mountain? What instrument measures air pressure? Global Winds What roles do composition, structure, and properties play in our atmosphere? Coriolis Effect Because the Earth rotates, and consists of a mixture of land and sea, the Coriolis Effect exists The Coriolis Effect causes air movement to: Move to the RIGHT in the Northern Hemisphere Move to the LEFT in the SOUTHERN Hemisphere Coriolis Effect Global Winds Global wind patterns are caused by: Coriolis Effect The land and sea makeup of Earth Warm Moist Air Rises Cool Dry Air Sinks Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises Cool Dry Air Sinks Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises Very Cold Air Sinks Cold Moist Air Rises Cool Dry Air Sinks Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises Very Cold Air Sinks Very Cold Air Sinks H L Cold Moist Air Rises H Cool Dry Air Sinks L Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises Very Cold Air Sinks H L H H L H L H L H Wind Moves from HIGH to LOW Objects are deflected to the RIGHT in the Northern Hemisphere 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 Remember! Wind gets its name from the direction it is blowing FROM! 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. Trade Winds • 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. Prevailing Westerlies • Strong winds • Located in the belt from 30-60 degrees latitude in both hemispheres. • Has an impact on the US weather Polar Easterlies • Cold, but weak winds • Near the north and south poles • US weather is influenced by these • Cooling takes place between the 50-60 degree latitude as it approaches the poles Northern Wind Patterns Polar Easterlies 90 – 60 latitude from the east Prevailing Westerlies 60 – 30 latitude from the west Trade winds 30 – 0 latitude from the East Latitude Nicknames Horse Latitudes 30 latitude Named because the boats stalled and the horses had to go! Doldrums / Intertropical Convergence Zone (ITCZ) Equator Trade winds converge from north and south Named because boats also got stranded here Jet Streams Jet Streams form at latitudes where wind systems come together High speed westerly winds form high above the surface There are 2 types of winds… 1. Local Winds 2. Global Winds Jet 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, moving storms What brings certain weather phenomenon? El Nino La Nina • occurs when the surface occurs when the surface temperature rises above the temperature falls below the normal water temperature in normal water temperature in the Equatorial Pacific Ocean the Equatorial Pacific Ocean creating more humidity in the creating a more dry atmosphere atmosphere Known to create drought • Known to increase number of conditions hurricanes • Occur more frequently (every 37 years) 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 What’s the difference? How do sea and land breezes work?