Wind Notes

Wind is the horizontal movement of air that moves from areas of high pressure to areas of low pressure. Wind is described by its direction and its speed. Winds are named by the direction they blow from. (for example, a prevailing westerly blows from the west) Wind speed is measured by an anemometer.

What causes the wind to blow? As the sun warms the Earth's surface, the atmosphere warms too. Some parts of the Earth receive direct rays from the sun all year and are always warm. Other places receive indirect rays, so the climate is colder. Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow. All winds are caused by differences in air pressure.

Winds are created when…. warm air rises creating low pressure. Cool, more dense air comes in to replace the warm air creating high pressure. • As air goes from areas of high to low pressure, winds form.

Winds are caused by convection currents, just like deep ocean currents and convection in the mantle.

2 types of winds: local winds 2. global winds

1. local winds cover short distances • blow from any direction • 2 types of local winds: – sea breezes- blow from sea to land – land breezes – blow from land to sea *Both are created because the land heats up and cools off faster than the sea.

animation of sea and land breezes http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm?chapter_no=visualization animation of sea and land breezes

sea breeze

land breeze

caused by differences in density blow over long distances global winds caused by differences in density blow over long distances curve because of the Coriolis Effect. (Coriolis Effect – rotation of the Earth causing moving air and water to curve) Northern Hemisphere -winds curve to the right Southern Hemisphere- winds curve to the left.

types of global winds: -calm winds: doldrums horse latitudes – strong winds: trade winds prevailing westerlies polar easterlies *Remember: winds are named by the direction they come from.

global winds animations http://www3.interscience.wiley.com:8100/legacy/college/strahler/0471238007/animations/ch07_animations/animation3.html http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp29/animations/ch29/global_wind_circulation.swf http://www.phschool.com/webcodes10/index.cfm?wcprefix=cfp&wcsuffix=4023&fuseaction=home.gotoWebCode&x=0&y=0. This one has a game you can play at home!

doldrums at the equator, surface winds are calm and weak.

horse latitudes found at 30 degrees North and 30 degrees South latitude (of the equator) calm winds called this because sailors had to throw horses overboard when they got caught in these winds (or lack of winds)

trade winds • 30 degrees N & S of equator and blow towards the equator. • steady winds that enabled sailors to carry cargo from Europe to the West Indies and South America.

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 • 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

jet stream • discovered in 1940’s • can be found in the upper troposphere 10 km above Earth • strong high speed and high pressure • moves west to east across the US, moving storms

brainpop movie on wind http://www.brainpop.com/science/weather/wind/