WIND What causes wind? AAAAll winds are caused by differences in air pressure. WWWWind is the horizontal movement of air from an area of high.

WINDWIND

What causes wind?What causes wind?

All winds are caused by differences in All winds are caused by differences in air pressure.air pressure.

Wind is the horizontal movement of air Wind is the horizontal movement of air from an area of high pressure to an from an area of high pressure to an area of low pressure.area of low pressure.

Differences in air pressure is caused Differences in air pressure is caused by unequal heating of the atmosphere. by unequal heating of the atmosphere.

Measuring WindMeasuring Wind

South winds blow from the south South winds blow from the south toward the north. North winds blow toward the north. North winds blow from the north toward the south.from the north toward the south.

An anemometer measures wind speed.An anemometer measures wind speed. An example of wind chill factor is if it is An example of wind chill factor is if it is

20 F and the wind speed is 30 mph the 20 F and the wind speed is 30 mph the wind chill factor makes it feel like -18 wind chill factor makes it feel like -18 F.F.

Local WindsLocal Winds

They blow over a short distance.They blow over a short distance. They are caused by unequal heating of They are caused by unequal heating of

Earth’s surface within a small area.Earth’s surface within a small area. They form only when no winds are They form only when no winds are

blowing from far away.blowing from far away.

Sea BreezesSea Breezes

Occur during the day.Occur during the day. The land will heat up faster during the The land will heat up faster during the

day than the water.day than the water. The cool air blows inland from the The cool air blows inland from the

water pushing up the warm air.water pushing up the warm air. The wind that blows from the water is The wind that blows from the water is

known as sea breezes. known as sea breezes.

Land BreezesLand Breezes

Occur during the night.Occur during the night. The land cools off more quickly than The land cools off more quickly than

the water.the water. Therefore the cool air moves over the Therefore the cool air moves over the

water causing the warmer air to rise.water causing the warmer air to rise.

Global WindsGlobal Winds

They are long distance winds that blow They are long distance winds that blow steadily from specific directions.steadily from specific directions.

The movement of air between the equator The movement of air between the equator and the poles produces global winds.and the poles produces global winds.

The Coriolis effect is wind curvature due to The Coriolis effect is wind curvature due to Earth’s rotation.Earth’s rotation.

If the Earth didn’t rotate, the wind would If the Earth didn’t rotate, the wind would blow in a straight line from the poles toward blow in a straight line from the poles toward the equator.the equator.

Global Wind BeltsGlobal Wind Belts

Major Major wind belts wind belts are trade are trade winds, winds, prevailing prevailing westerlieswesterlies, and , and polar polar easterlies.easterlies.

DoldrumsDoldrums

Very little horizontal movement.Very little horizontal movement. Region near equator with little or no Region near equator with little or no

wind.wind.

Horse LatitudeHorse Latitude

30 degrees N latitude30 degrees N latitude 30 degrees S latitude30 degrees S latitude

Trade WindsTrade Winds

Winds in the Northern hemisphere between Winds in the Northern hemisphere between 30 degrees N latitude and the equator blow 30 degrees N latitude and the equator blow generally from the northeast.generally from the northeast.

Winds in the southern hemisphere between Winds in the southern hemisphere between 30 degrees S latitude and the equator blow 30 degrees S latitude and the equator blow generally from the southeast.generally from the southeast.

Hundreds of years ago, sailors relied on the Hundreds of years ago, sailors relied on the trade winds to carry cargo from Europe to trade winds to carry cargo from Europe to the West Indies and South America.the West Indies and South America.

Prevailing WesterliesPrevailing Westerlies

They blow generally from the They blow generally from the Southwest between 30 degrees N and Southwest between 30 degrees N and 60 degrees N latitude.60 degrees N latitude.

They blow from the northwest They blow from the northwest between 30 degrees S and 60 degrees between 30 degrees S and 60 degrees S latitude.S latitude.

They play an important role in the They play an important role in the weather of the United States.weather of the United States.

Polar EasterliesPolar Easterlies

The coriolis effect shifts polar winds to The coriolis effect shifts polar winds to the west.the west.

They meet the prevailing westerlies at They meet the prevailing westerlies at about 60 degrees N and 60 degrees S about 60 degrees N and 60 degrees S latitude.latitude.

Jet StreamsJet Streams

10 km above the earth’s surface are 10 km above the earth’s surface are bands of high-speed winds.bands of high-speed winds.

They blow from the west to the east at They blow from the west to the east at speeds of 200-400km/h.speeds of 200-400km/h.

Airplanes are aided by the jet stream Airplanes are aided by the jet stream when traveling east.when traveling east.

Airplanes flying at jet stream altitudes Airplanes flying at jet stream altitudes are slowed down when traveling west are slowed down when traveling west against the jet stream winds. against the jet stream winds.