Think it Over. Now that we have completed the activity, make any necessary changes to your prediction.

Transcription

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2 Think it Over What do global wind patterns look like? Draw your prediction on your sheet. Now, let s try something. Does the wind turn? Let s find out! Now that we have completed the activity, make any necessary changes to your prediction.

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4 What is Wind? The horizontal movement of air from High pressure to Low pressure. H L Air moving up or down (vertical) is called a current

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6 Pressure is caused by the characteristics of the air Warmer Air X X X X X X X X X X X X Molecules move faster and are farther apart. Less Pressure; Less Dense Cooler Air X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Molecules are close together and move slowly. More Pressure; More Dense

7 Warm Air Rises Cool Air Sinks Cool Air Sinking Warm Air Rising

8 The unequal heating of air creates convection currents which then creates winds Air further from the earth s surface is cooler so the temperature of the air drops. As the air cools, it becomes more dense and starts to sink. Warmer, less dense air is pushed up by the cooler, denser air. Sinking air moves under warmer air, pushing the warmer air up.

9 So let s put it all together Winds form when Air is HEATED causes a decrease in pressure/density = 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

10 There Are Two Kinds of Winds: Global and Local Global Winds are Winds that blow over long distances around the Earth. Local Winds are winds that blow a short distance.

11 Why Do Different Parts of the Earth Have Different Temperatures? North Pole Equator South Pole Radiation is more intense near the equator compared to the poles. For this reason, it s warmer near the equator than at the poles.

12 Global Thermal Temperatures

13 Air Rises at the Equator Air at the Equator is warm Warm air rises The Equator is a Low Pressure area

14 What Happens to Rising Air at the Equator? At the Equator, air rises As the air moves upward, it cools The air begins to turn to move downward Cold air sinks at the 30 o zone

15 Winds blow from High Pressure to Low Pressure

16 Let s Label High Pressure 90 N Low Pressure 60 N High Pressure 30 N Low Pressure 0 High Pressure 30 S Low Pressure 60 S High Pressure 90 S

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18 Names of Winds North winds comes from the north South winds come from the south Southeast winds come from the southeast and blow northwest Northeast winds come from the northeast and blow to the southwest

19 Let s Label Easterlies Polar Easterlies Trade Winds Trade Winds Polar Easterlies

20 Polar Easterlies Cold, high pressure winds coming from both the north and south pole Move east (thus called easterlies )

21 Trade Winds The TRADE WINDS are the blowing towards the equator These winds are Easterlies, blowing from the east South of the equator, the winds blow from the southeast North of the equator, the winds blow from the northeast They were named because traders from Europe sailed in these zones on their way to the new world

22 Let s Label Westerlies Prevailing Westerlies Prevailing Westerlies

23 Prevailing Westerlies Move toward the poles Curve to the east (because they come from the west) Responsible for many of weather movements across the United States and Canada

24 DMS is in the Prevailing Westerlies Region

25 Zones of NO WIND Doldrums At the equator, which is 0 o latitude, there is a windless zone called the Doldrums Horse Latitudes At 30 o N and 30 o S, there is a windless zone called the Horse Latitudes

26 Horse Latitudes And The Doldrums

27 Doldrums Since the Trade Winds blow from both the North and South, a calm zone occurs This zone is called the DOLDRUMS In this zone, there are no winds. Ships often got stalled for long periods because they needed wind to blow their sails.

28 Horse Latitudes zones of calm winds at the 30 o Latitude Lines. The term horse latitudes originates from the days when Spanish sailing vessels transported horses to the West Indies. Since there was no wind, the sail ships that entered this zone, would get stuck for weeks. Since water and food shortages occurred, the crews found it necessary to throw their horses overboard.

29 30 o North and South Latitude This is an area of high pressure Air from the Equator and from the 60 o Latitudes cool and descend (sink) at the 30 o Latitude. Sinking air means no clouds or rain. Along this latitude, (between 15 o to 35 o ) many of the major deserts are found

30 Why Don t The Winds Blow in Straight Lines? Cold air from both the South Pole and North Pole blows towards the 60 o zone But the air doesn t flow in a straight line

31 Coriolis Effect Since the earth rotates, winds do not blow directly from north to south or south to north Winds curve They curve because the earth rotates or spins on its axis The Coriolis Effect is the curving of fluids (liquids/gases) due to the earth s rotation Northern Hemisphere winds curve to the right Southern Hemisphere winds curve to the left

32 The ball is going straight, but it looks like it is curving.

33 Global Wind Animation ~tbw/wc.notes/7.circ.atm/animati ons/globalwind.html

34 Local Winds Winds that blow short distances and in any direction (depending on pressure) Remember, winds always blow from areas of high pressure to low pressure.

35 Sea Breeze During the day, land warms faster than water Warm air over land rises Cooler air over water sinks and moves to replace warm air As warm air rises expands and cools As cools becomes more dense sinks back down Cooler Air Sinks

36 Land Breeze At night, dry land cools faster than water Air above water warmer & less dense than air above dry land Convection current goes in opposite direction of daytime Warmer air rises above water Cooler air from land sinks and goes out over water Cooler Air Sinks