Investigation 8 part 2 What Causes Wind 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? As air warms, it expands. Air rises There is less air pushing down 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? As air cools, it contracts. Air sinks There is more air pushing down Air pressure increases

Wind How can air move sideways across the surface of the Earth?

Wind? How is wind made? Cause wind? 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, less- dense 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 Low pressure area High pressure area Differential heating and cooling off affects energy transfer to and from the atmosphere Rising warm air and sinking cool air produce convection currents Differences in atmosphere pressure causes air to move Air moving across Earth’s surface is wind

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 Winds Landmasses 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: Landmasses Conduction (air molecules make contact with land and water surfaces) Reradiation of energy from the surface

Air expands and becomes less dense Local Winds 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

Visualization Exercise 8.3 Labels and Arrows >>>next slide<<< Visualization Exercise 8.3

Resources, P. 54 Exercise 8.3 Image comprehension focus: labels and arrows Rationale: This activity is designed to briefly reinforce the idea that reading labels is a very important part of being able to understand a diagram as well as understanding the role(s) that arrows can play in a diagram, and that it is important not to assume that all arrows play the same role(s) in each diagram. Type of Activity: Teacher-guided student activity Objective: To reinforce the importance of reading labels as well as understanding one role that arrows can play in a diagram. Module Images: Resources, pg. 54 Procedure: Project the above image of a convection cell from page 54 of the Resources book. After giving the students an opportunity to study the diagram, ask students the following questions: “What is being represented by the purple shaded area beneath the convection cell?” [The Earth] “What do the numbers mean?” Explain: “The numbers are the degrees of latitude that indicate an angular position north and south of the equator.” Ask: “Where is the equator in this image?” Explain: “The equator can be found at the 0-degree mark, but the perspective of the image may make this tricky. The equator can be thought of as running straight out of the picture – it is as though the reader is standing on the equator and looking along it.” Ask: “What is the role of the black arrows at the bottom of this image?” Explain: “These arrows represent the direction of the latitude points. That is, the arrow on the left is indicating increasing latitude towards the South, while the arrow on the right represents increasing latitude towards the North.” You should emphasize to students the importance of paying attention to all labels and arrows, as it would be very difficult to understand the image without the use of these tools. >>>end of exercise<<<

Color, Labels, and Arrows >>>next slide<<< Visualization Exercise 8.4

Images: CD-Rom Exercise 8.4 Image comprehension focus: Color, labels, and arrows Rationale: Often, diagrams will employ the use of color. Sometimes with these diagrams, a specific color may be used to illustrate a specific point or concept even using similar color schemes across different images, whereas sometimes it is not the specific color used that is important, only that there are different colors being used. This exercise is designed to briefly illustrate one way that color can be used in a diagram as well as to re-emphasize the importance of labels and arrows. Type of Activity: Teacher guided student activity Objective: To briefly review the role(s) that color, labels, and arrows can play in a diagram. Module Images: CD-Rom Procedure: Project the above image and, either individually or in small groups, ask students the following questions: Ask: “What are three different ways you can tell what is happening to the air in the diagram.” [Note that students may not be able to come up with all three ways (listed below) but should be given the opportunity to present as many ideas as they have. If necessary, point out those that the students have not volunteered]. Explain: “One way to know what is going on with the air would be to read the explanatory labels which explain, in the most obvious sense what is going on with the air.” [Here the teacher can point out the specific explanatory labels]. Explain: “A second way to know what is happening with the air is to pay attention to the roles that the arrows play. The arrows show that the air is moving in a circular path.” Explain: “A third way to know what is happening with the air is to note the specific colors of the arrows. Specifically, the author has chosen to use blue and red, colors that are common used to indicate when something is ‘cool’ (blue) or ‘warm’ (red). It is important to be aware of all three ways in order to gain the most comprehensive understanding of the concept being presented.” Ask: “When hot and cold air moves in a circular pattern like this, what do we call it?” [This is an example of convection.] >>end of exercise<<<

Arrows, Color and Real vs Diagram >>>next slide<<< Visualization Exercise 8.5

Resources, P. 58 Exercise 8.5 Image comprehension focus: Arrows, color, and real vs. diagram Rationale: This activity is designed to not only briefly review possible roles of arrows and color in diagrams, but also to emphasize the difference between diagrams and real images. Understanding the difference between a diagram and what is ‘real’ can help to prevent misconceptions that students can have when they think that the diagram is an exact representation of real life. Type of Activity: Teacher guided student activity Objective: To re-emphasize the role(s) of arrows and color, as well as reinforce student understanding of real vs. diagram. Module Images: Resources pg. 58 Procedure: Project the above image from page 58 of the Resources book and have students briefly study the diagram. Next, either individually or in small groups, ask students to explain the following: The role of the white arrow Explain: “This arrow shows which direction the wind is blowing” The role of the black arrows Explain: “These arrows show the direction that the thermal bubbles move, as they rise higher into the sky.” [Here, the you can also take the opportunity to point out that the roles of both types of arrows are similar, in the sense that each is indicating a sense of movement and direction]. Ask: “How can you tell that the thermal bubbles pictured here are part of a diagram as opposed to a real image?” [Here, the students may have several answers. They may talk about the color or the fact that one cannot see actual arrows in the sky. You should help guide students to the answer that thermal bubbles are actually invisible, but that the author has drawn in the bubbles in order to help the reader understand this concept]. Ask: “Why did the author choose to draw the thermal bubbles using the light blue color? [Again, if students have difficulty with this, you should assist students by pointing out that the thermal bubbles are actually warm air, and that the author chose light blue to represent warm air in this image. Therefore, the bubbles would also need to be drawn using this same color]. >>>end of exercise<<<

Reading Starting on page 53 of your resource book read “Where the Wild Winds Blow”. Answer the “Think Questions” on page 55.