Science Lesson: Winds Go Spinning Around

Abstract
In this lesson, students will simulate the Coriolis Effect to understand why winds in the Westerlies are prone to cyclonic and anti-cyclonic motion.
Purpose – Explanation of processes that drive world wind patterns.

Objectives
Students will be able to:
1. Recognize and articulate in discussion and in written responses the effect the Coriolis Force has upon wind patterns (deflecting winds right in the Northern Hemisphere and left in the Southern Hemisphere)

National Science Education Standard:
CONTENT STANDARD D: Earth and Space Science
ENERGY IN THE EARTH SYSTEM
∑ Earth systems have internal and external sources of energy, both of which create heat. The sun is the major external source of energy. Two primary sources of internal energy are the decay of radioactive isotopes and the gravitational energy from the earth’s original formation.

∑ Heating of earth’s surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents.

∑ Global climate is determined by energy transfer from the sun at and near the earth’s surface. This energy transfer is influenced by dynamic processes such as cloud cover and the earth’s rotation, and static conditions such as the position of mountain ranges and oceans.

GEOCHEMICAL CYCLES
∑ Movement of matter between reservoirs is driven by the earth’s internal and external sources of energy. These movements are often accompanied by a change in the physical and chemical properties of the matter. Carbon, for example, occurs in carbonate rocks such as limestone, in the atmosphere as carbon dioxide gas, in water as dissolved carbon dioxide, and in all organisms as complex molecules that control the chemistry of life.

Teacher Background
The Coriolis Force affects global wind patterns and is responsible for the cyclonic and anti-cyclonic wind patterns in the Westerlies in both the Northern and Southern Hemispheres.
Coriolis Force – Film clip of ball on merry-go-round
(http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/fw/crls.rxml)

Related and Resource Web sites
Global Composite Animation (Shows Global Air Currents – good views of Trades and Westerlies)
http://www.atmo.arizona.edu/products/wximagery/globalir.html

Global Water Vapor Animation (Shows Motion of Vapor in the Atmosphere - good views of Trades and Westerlies)
http://www.atmo.arizona.edu/products/wximagery/globalwv.html

Earth Probe TOMS Aerosol Index (Shows Trades and southern Westerlies nicely, you need to cut and paste this address into the web to get it to show the animation.)
http://science.nasa.gov/headlines/images/dust-quicky/dustmovie_big.gif

Meteosat Infrared Satellite Data from NASA
Global Composite Satellite Data from NASA
Global Composite Water Vapor Satellite Data
http://wwwghcc.msfc.nasa.gov/GOES/ (menu screen here provides access to above maps - good views of Trades and Westerlies – set the image loop as high as possible so the students get the most time possible to observe wind motion)

Animated Global IR
http://www.cpc.noaa.gov/products/global_precip/html/wpage.gl_ir_loop.html

Activity
1. At the beginning of class show the global picture of the Earth’s wind patterns again (any of the above will do). Ask students to pay attention to swirling winds in the Westerly wind belts. What do they notice about the air currents? [The Westerlies are prone to cyclonic action]. What direction do the cyclones move? [To the right in the northern hemisphere and to the left in the southern hemisphere].

2. Using their understanding from the pervious lessons, ask them to try to explain why the winds move in cyclonic action. (Don’t be surprised if students have difficulty with this; the rest of the lesson will make the Coriolis Effect apparent to them.)

3. After students have made a significant attempt to explain why the winds are deflected, have them answer the following question: How is the Earth like a merry-go-round?

4. Allow students a few minutes to answer the question and to share their responses with the class. Expect “both spin” to be a top response.

5. Ask students what happens when you toss something to your friend if you are riding on two different horses on a merry-go-round right next to each other? [Your friend will have a hard time catching the ball] From the point of view of either yourself or your friends, what direction does the ball go (straight or curved?) [It appears to be thrown behind, in a curve.]

6. Ask students what they think the ball would look from above. Record students’ answers then show the clip from the following site: (http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/fw/crls.rxml). As the students can clearly see from the film clip, the ball moves in a straight line when viewed from above. The ball only curves from the point of view of those on the merry-go-round.

7. Ask students to think about wind. How might the ball be like wind? [Wind blows in a straight line, but is deflected like the ball].

8. Now take out the turntable, place the circular paper in the center and slowly spin the turntable. While you are spinning the table, draw a straight line from the center to the edge. What do students notice when you take the paper off the turntable. [The line is curved.]

9. How is this like the earth and winds/clouds? [As the winds move they appear to be pushed to the side in a curving motion.]

10. Ask students to consider why the winds are not all deflected equally.

11. Ask students to think about being bumped in the hall. When is the effect more obvious, when they are walking or running? [Running] Which winds will be more deflected by the Coriolis Effect? [faster moving winds]

Closure
Can students explain how the spinning of the Earth affects the apparent motion of the clouds?

Embedded Assessment
Throughout class discussions and in written responses, students should be able to explain the apparent motion of clouds as they relate to the Coriolis Force.