WindWind

What is wind?What is wind?

Wind is air in motion. Wind is air in motion.

It is produced by the uneven heating It is produced by the uneven heating of the earth’s surface by the sun. of the earth’s surface by the sun. Since the earth’s surface is made of Since the earth’s surface is made of various land and water formations, it various land and water formations, it absorbs absorbs the sun’s the sun’s radiation radiation unevenly. Two factors are unevenly. Two factors are necessary to specify wind: necessary to specify wind:

speed and direction. speed and direction.

What causes wind?What causes wind?

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

How can the wind be How can the wind be harmful?harmful?

Wind can be harmful when it brings:Wind can be harmful when it brings:

thunderstormsthunderstorms hurricaneshurricanes tornadoestornadoes erosionerosion

How is wind helpful?How is wind helpful?

Wind is the fastest growing source of Wind is the fastest growing source of electricity in the world. It's often one of electricity in the world. It's often one of the least expensive forms of renewable the least expensive forms of renewable power available. Some experts say it power available. Some experts say it can sometimes be the cheapest form can sometimes be the cheapest form of any kind of power. Generating power of any kind of power. Generating power from the wind leaves no dangerous from the wind leaves no dangerous waste products behind. Best of all, its waste products behind. Best of all, its supply is unlimited.supply is unlimited.

Windmills work because they slow Windmills work because they slow down the speed of the wind. The down the speed of the wind. The wind flows over the airfoil shaped wind flows over the airfoil shaped blades causing lift, like the effect on blades causing lift, like the effect on airplane wings, causing them to turn. airplane wings, causing them to turn. The blades are connected to a drive The blades are connected to a drive shaft that turns an electric generator shaft that turns an electric generator to produce electricity. to produce electricity.

What is the purpose of an What is the purpose of an anemometer?anemometer?

An anemometer measures the wind An anemometer measures the wind speed and is made of propeller cups speed and is made of propeller cups which are rotated by the motion of which are rotated by the motion of the wind. The essential parts of the the wind. The essential parts of the cup anemometer are the cup wheel, cup anemometer are the cup wheel, a vertical shaft, the necessary a vertical shaft, the necessary mechanism for counting the mechanism for counting the revolution of the shaft or indicating revolution of the shaft or indicating its instantaneous speed of rotation.its instantaneous speed of rotation.

What is the purpose of a What is the purpose of a weather vane or a wind weather vane or a wind

vane?vane?

A wind vane is used to indicate wind A wind vane is used to indicate wind direction. It consists basically of an direction. It consists basically of an asymmetrically shaped object with its asymmetrically shaped object with its center of gravity about a vertical axis. The center of gravity about a vertical axis. The front end of this object (in most cases an front end of this object (in most cases an arrow) which offers the greater resistance arrow) which offers the greater resistance to the motion of the air points to the to the motion of the air points to the direction from where the wind blows. The direction from where the wind blows. The direction of the wind is determined by direction of the wind is determined by reference to an attached oriented compass reference to an attached oriented compass point. point.

What is the difference between What is the difference between local and prevailing winds?local and prevailing winds?

Local winds depend on local changes Local winds depend on local changes in temperature. They affect only a in temperature. They affect only a small area of land.small area of land.

Sea BreezesSea Breezes

On a warm summer day along the coast, On a warm summer day along the coast, this differential heating of land and sea this differential heating of land and sea leads to the development of local winds leads to the development of local winds called sea breezes. As air above the land called sea breezes. As air above the land surface is heated by radiation from the surface is heated by radiation from the Sun, it expands and begins to rise, being Sun, it expands and begins to rise, being lighter than the surrounding air. To replace lighter than the surrounding air. To replace the rising air, cooler air is drawn in from the rising air, cooler air is drawn in from above the surface of the sea. This is the above the surface of the sea. This is the sea breeze, and can offer a pleasant sea breeze, and can offer a pleasant cooling influence on hot summer cooling influence on hot summer afternoons.afternoons.

A land breeze occurs at night when A land breeze occurs at night when the land cools faster than the sea. In the land cools faster than the sea. In this case, it is air above the warmer this case, it is air above the warmer surface water that is heated and surface water that is heated and rises, pulling in air from the cooler rises, pulling in air from the cooler land surface.land surface.

land breezeland breeze

global wind patternsglobal wind patterns

Prevailing winds are caused by Prevailing winds are caused by uneven heating of large parts of uneven heating of large parts of Earth’s atmosphere and by its Earth’s atmosphere and by its rotation.rotation.

Trade windsTrade winds

The trade winds are just air The trade winds are just air movements toward the equator. movements toward the equator. They are warm, steady breezes that They are warm, steady breezes that blow almost continuously. The blow almost continuously. The Coriolis Effect makes the trade winds Coriolis Effect makes the trade winds appear to be curving to the west, appear to be curving to the west, whether they are traveling to the whether they are traveling to the equator from the south or north.equator from the south or north.

jet streamjet stream

The jet stream is a fast flowing, river of air The jet stream is a fast flowing, river of air found in the atmosphere at around 12 km found in the atmosphere at around 12 km above the surface of the Earth just under above the surface of the Earth just under the tropopause. They form at the the tropopause. They form at the boundaries of adjacent air masses with boundaries of adjacent air masses with significant differences in temperature, such significant differences in temperature, such as of the polar region and the warmer air to as of the polar region and the warmer air to the south. Because of the effect of the the south. Because of the effect of the Earth's rotation the streams flow west to Earth's rotation the streams flow west to east, propagating in a serpentine or wave-east, propagating in a serpentine or wave-like manner at lower speeds than that of like manner at lower speeds than that of the actual wind within the flow.the actual wind within the flow.

sourcessources

http://www.weatherwizkids.com/wind1.htmhttp://www.weatherwizkids.com/wind1.htm http://upload.wikimedia.org/wikipedia/comhttp://upload.wikimedia.org/wikipedia/com

mons/6/6d/Wind_vane_05643.jpgmons/6/6d/Wind_vane_05643.jpg http://z.about.com/d/mandarin/1/0/f/c/-/-/wihttp://z.about.com/d/mandarin/1/0/f/c/-/-/wi

ndy_5.pngndy_5.png http://teachers.henrico.k12.va.us/http://teachers.henrico.k12.va.us/

freeman/kertis_j/Global%20and%20Localfreeman/kertis_j/Global%20and%20Local%20Winds.ppt#260,5,Pressure Belts %20Winds.ppt#260,5,Pressure Belts