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Day 42 Investigation 8 part 2 What Causes Wind Convection Chamber Review Air is cooled at the top of the chamber because of the ice Air warmed by candle rose to the top because it is less dense Air sinks because it is denser Conclusion Warm, less-dense air rose; Cooler, denser air sank Creates a convection cell Review Convection Cell on Earth Where on Earth’s surface could a convection cell develop? Where Earth’s surface is warm •Desert •Tropical ocean What happens to air pressure If warm air less dense and rises, what effect do you think that has on air pressure on the ground? 1. As air warms, it expands. 2. Air rises 3. There is less air pushing down 4. Air pressure decreases What happens to air pressure If cool air denser and sinks, what effect do you think that has on air pressure on the ground? 1. As air cools, it contracts. 2. Air sinks 3. There is more air pushing down 4. Air pressure increases Wind • How can air move sideways across the surface of the Earth? Wind? • How is wind made? –Differential heating of Earth’s surface –Energy transfer (radiation, conduction, convection) –Air pressure –Density • Cause wind? Wind Concepts • Differential heating and cooling affects energy transfer to and from the atmosphere • Warm air expands and is less dense • Cool air contracts and is denser • Rising warm air and sinking cool air produce convection currents Wind Concepts (part 2) • Dense air produces high-pressure areas, lessdense air produces low-pressure areas • Differences in atmospheric pressure causes air to move • Air moving across Earth’s surface is wind Wind Concepts Cool air contracts and becomes denser Warm air expands and becomes less dense Differential heating and cooling off affects energy transfer to and from the atmosphere Low pressure area Differences in atmosphere pressure causes air to move Air moving across Earth’s surface is wind High pressure area Rising warm air and sinking cool air produce convection currents Multimedia • Watch the different types of local winds. • On pages 48 and 49 of the student lab book draw an illustration of the local winds after previewing the multimedia. • Local weather conditions influence local winds Which absorbs and releases solar energy faster, landmasses or water? Energy transfer to and from the air in the atmosphere: 1. Conduction (air molecules make contact with land and water surfaces) 2. Reradiation of energy from the surface • What happens to air when it is heated? Air expands and becomes less dense What happens to air pressure over the land when air warms and expands? Pressure decreases, local low pressure forms Wind • The horizontal movement of air from an area of high pressure to an area of lower pressure Naming Local Winds • Local winds are named based on the direction they come from • A North wind is blowing from the North to the South Sea Breeze • Occurs during the day. • The flow of air from an ocean or lake to the land. Land Breeze • Occurs at night • The flow of air from land to a body of water. Valley Breeze Occurs during the day when air over the mountains heats and rises The flow of air from the valley up through the mountain Mountain Breeze Occurs at night when air cools high in the mountains and sinks into valleys Labels and Arrows Visualization Exercise 8.3 Resources, P. 54 Color, Labels, and Arrows Visualization Exercise 8.4 Images: CD-Rom Arrows, Color and Real vs Diagram Visualization Exercise 8.5 Resources, P. 58 Reading • Starting on page 53 of your resource book read “Where the Wild Winds Blow”. • Answer the “Think Questions” on page 55.
