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WINDS

WINDS. Understand the cause of wind and how they affect climate Chapter 4 Pages 59-67. What is Wind?. A wind is a horizontal movement of air across a surface. Vertical movements are currents or updrafts and downdrafts Caused by what????

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WINDS

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  1. WINDS Understand the cause of wind and how they affect climate Chapter 4 Pages 59-67

  2. What is Wind? • A wind is a horizontal movement of air across a surface. • Vertical movements are currents or updrafts and downdrafts • Caused by what???? • Heat versus cold!! Relate it to convection cells previously studied!!!

  3. What causes wind? • Unequal heating • Unequal heating causes pressure differences • Cold, heavy air sinks = high pressure • Warm, expanding air rises = low pressure • Winds blow from high to low

  4. Know that air blows from areas of high pressure to areas of low pressure. • The statement is fact. • Think: • Air inside a balloon • Exhaling • Air powered pellet gun • It is simply fact. • High and low pressures in the earth’s atmosphere are responsible for wind • P. 59-61

  5. Application - Land Breeze • Using your knowledge of wind predict & explain the wind direction below. P. 61 • FACT: Water holds heat longer than the land. • During the night, sea air is warmer than the air over the land. • Air rises over sea • Relative Low pressure over sea • Land air moves to lower pressure Low Pressure

  6. Land Breeze • Night time • Cool breeze • Off the land

  7. Application - Sea Breeze • Using your knowledge of wind predict & explain the wind direction below. P. 61 • FACT: Land heats up faster than the water • During the day, air over the land is warmer than air over the sea • Air rises over land • Relative Low pressure over land • Sea air moves to lower pressure • Cold “Breeze” off the ocean during the day Low Pressure

  8. Sea Breeze • Day time • Cool Breeze • Off the ocean

  9. Define the terms wind & prevailing wind. p.61-63 Wind: • is a horizontal movement of air across a surface. • It results from air masses of different temperatures and humidity lying next to each other. • The resulting pressure variation causes “wind” to blow from high pressure areas to low pressure areas. Prevailing Wind: • Is regular, predictable, normal wind direction for a given area or region. • Caused by global convection cells. • Named after the direction from which it comes

  10. Prevailing Winds Lab

  11. Prevailing Winds

  12. Describe how the coriolis force affects wind direction. Coriolis force = • objects in motion tend to deflect • to the right in north hemisphere • to the left in south hemisphere Consequently winds: • in the northern hemisphere tend to curve to the right of their path. • while in the southern hemisphere they deflect left of their path.

  13. Summary of prevailing wind • Global highs and lows are due to uneven heating of the earth • Air moves from high pressure to low pressure creating winds • Winds are deflected in the directions indicated on the diagram due to the coriolis effect.

  14. Make inferences about how winds are related to major pressure belts. p.63 • Air rises at the equator • It settles at the poles • Result = 6 convection cells • 3 above and 3 below the equator. • Low pressures result where hot air rises. • High pressures result where air settles

  15. Describe Orographic rainfall p. 66 Leeward Chinook • A relatively warm, moist air blows off the sea • It is forced up by mountains (high relief) • Air cools at higher altitude • Cool air holds less moisture • Consequently clouds condense and rain falls • Most rain falls on the windward side of the relief • Leeward side is often in a dry rain shadow because the moisture has all been lost Windward

  16. Definitions • Windward • The side of the mountain receiving the wind • (consequently more precipitation as well) • Leeward • The side of the mountain sheltered from the wind • (consequently receives less precipitation) • Rain Shadow • The area located on the leeward side of a mountain that receives low amounts of precipitation. • Mainly due to the air that descends on the leeward side has “dumped” on the windward side.

  17. Describe Frontal rainfall p. 66 • Weather Front-2 fronts meet • Hence the name frontal rain • Warm Moisture laden air meets cold air • Warm air is less dense & is forced up over the cooler, more dense air • Warm Moisture laden air cools at higher altitude • Cool air holds less moisture • Consequently clouds condense and rain falls FRONT Warm, moist air

  18. Describe Convectional rainfall p. 67 • Often associated with thunder storms. • Usually occurs in hot areas like tropics or continental summer • Sun heats the earth causing large amounts of water to evaporate • Hot air rises forming convection currents (hence the name) • Warm Moisture laden air cools at higher altitude • Cool air holds less moisture • Consequently clouds condense and rain falls Air heated from the earth

  19. Analyze the relationship between wind systems and temperature. • How do the prevailing winds affect temperature in: • Argentina • Columbia • Baffin Island • Newfoundland

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  21. Analyze the relationship between wind systems and precipitation • How do the prevailing winds affect precipitation in: • England • Midwestern U.S. • British Columbia • Northern Africa • Central Australia • Question #26 p. 67 = great active learning lab

  22. A C B D E

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