Carolina TM Coriolis Effect and Atmospheric Circulation Kit STUDENT GUIDE

Transcription

1 Name: Date: Mods: Carolina TM Coriolis Effect and Atmospheric Circulation Kit STUDENT GUIDE Background Global air circulation is a major influence on the world's climates. Air circulation is caused by four factors uneven heating of the earth's surface, seasonal variation in temperature and precipitation, the rotation of the earth on its axis, and the physical properties of air, land, and water. The first two activities in this unit concentrate on how the rotation of the earth affects global air circulation. The last two activities look at how the uneven heating of the earth and the rotation of the planet affect wind patterns and the rotation of storms. Due to the earth s rotation, large air masses tend to be deflected to the right or left depending on whether they are moving across the Northern or Southern Hemisphere. This phenomenon is referred to as the Coriolis effect, named after French mathematician Gaspard Coriolis ( ), who analyzed it. The Coriolis effect is used to explain why objects moving in a straight path on an object that is rotating at a constant speed appear to be deflected to one side. The effect is perceived only from the rotating object. If viewed from a stationary point, the object appears to move in a straight line. If you visualize a rotating disk, you can see that not all points on the disk are moving at the same speed. If you made a line along the radius of a record player turntable and marked two points on the line, one at the outer edge and one close to the center, and then spun the turntable, both points would of course stay on the line. The outer point, however, would travel a greater distance over the same amount of time than the inner point. Now imagine person A on the outer edge of a merry- go- round. Person A has a ball and is going to roll it across the merry- go- round. If the merry- go- round is not rotating when person A rolls the ball, the ball will travel in a straight path when viewed from the merry- go- round and when viewed by person B standing nearby. However, if the merry- go- round is rotating and person A rolls the ball again, the ball s apparent path will curve based on person A s frame of reference. However, to person B standing on the ground outside the merry- go- round frame of reference, the ball still appears to travel in a straight line. The ball is, in fact, traveling in a straight line, but because the outer edge of the merry- go- round is rotating faster than the center, as the ball moves towards the center, it appears to move to the left or right, depending on the direction of the merry- go- round's rotation. The Coriolis effect on the movement of large air masses moving north or south is to deflect those in the Northern Hemisphere to the right and those in the Southern Hemisphere to the left. For example, an air mass moving from the North Pole toward the equator is deflected toward the west (to its right). One moving from the South Pole toward the equator is also deflected toward the west (but to its left).

2 The Coriolis effect is a critical component in the formation of large storm systems, such as hurricanes, cyclones, and typhoons. These storms begin with the heating of tropical waters. A heated air mass rises and moves toward the pole. The farther the mass moves from the equator, the greater its Coriolis deflection, setting in motion the storm's rotation. Interestingly, since there is no Coriolis effect at the equator, tropical cyclones tend to develop at least 500 km away from it, either to the north or south. The Coriolis effect also influences ocean currents and the global wind belts. Around the tropics, air at the earth's surface heats and rises, then moves toward the poles. Because of their higher altitude, the masses begin to cool, and their poleward movement becomes deflected because of the Coriolis effect. As they cool, the masses sink again, move back toward the equator as surface winds, and are deflected in the opposite direction. The overall effect is to create steady bands of wind flow around the globe. The tropical winds are called the trade winds. Other global winds produced by the Coriolis effect and by rising and falling air masses are the subtropical westerlies and the polar easterlies.

3 Activity 1: Rotation of the Earth Materials (per student group) 1 inflatable globe Procedure 1. Obtain the following materials for your group: an inflatable globe. 2. While one partner is holding the globe staight up and down with the North Pole at the top, have another group member stand opposite the person. Rotate the globe from west to east (Figure 1). We refer to the rotation of the earth as counterclockwise. Observe the direction rotation while looking at the equator. Observe both sides of the earth while it is rotating. 3. Now have one partner hold the globe at the South Pole and another partner at the other end at the North Pole and hold the axis horizontal. 4. Slowly rotate the globe in the same direction as before, from west to east (Figure 2). 5. Observe the direction the globe appears to spin while looking at the North Pole and then while looking at the South Pole. Refer to the rotation as clockwise or counterclockwise movement. (Refer to the rotation of a clock's hands if unsure of the direction for clockwise and counterclockwise rotation.)

4 Activity 2: Rotation in Two Dimensions Materials (per student group) 1 turntable 1 black dry- erase marker 1 green dry- erase marker Procedure 1. Obtain the following materials for your group: turntable, a black dry- erase marker, and a green dry- erase marker. 2. With the turntable stationary, have one member of your group draw a straight line from the edge to the center of the turntable, using the black marker. Label this line "R." This is your reference line. 3. Have one person in your group slowly and consistently rotate the turntable counterclockwise. 4. While the turntable is being rotated, have another person make a straight line starting at the edge and moving toward the center of the turntable, using the black marker. Observe the path of the marker. 5. Stop the turntable and label this line 1CCW (for first trial, counterclockwise). Place an arrowhead at the end of the line to indicate the direction the marker was moving. 6. Repeat steps 3 and 4 two more times. After each trial, stop the turntable and label the line with the trial number. 7. Repeat the process by rotating the turntable counterclockwise, but this time draw lines from the center toward the edge. Label the first line 4CCW (for fourth trial, counterclockwise). Again, place an arrowhead at the end to indicate the direction the marker was moving. Perform the trial two more times and label the lines. 8. Observe the lines that were made while the turntable rotated. Discuss the path of the marker during each trail with the members of your group. Answer Reflection Questions Erase the lines except for one that moves from the edge towards the center and one that moves from the center toward the edge. 10. With the turntable stationary, have one member of your group draw a straight line from the edge to the center of the turntable, using the green dry- erase marker. Label this line R. This is your clockwise reference line. 11. Have one person in your group slowly and consistently rotate the turntable clockwise. 12. While the turntable is being rotated, have another person make a straight line starting at the edge and moving toward the center of the turntable, using the green marker. Have the other members of your group observe the path of the marker. 13. Stop the turntable from rotating and label this line 1CW (for first trial, clockwise). Place an arrowhead at the end of the line to indicate the direction the marker was moving. 14. Repeat steps 10 and 11 two more times. After each trial, stop the turntable and label the line with the trial number. 15. Repeat the process by rotating the turntable clockwise but this time drawing lines from the center toward the edge. Label the first of these lines 4CCW (fourth trial, clockwise). Again, place an arrowhead at the end of the line to indicate the direction the marker was moving. Perform this trial two more times and label the lines. 16. Observe the lines that were made while the turntable rotated clockwise. Discuss the path of the marker during each trail with the members of your group. Also note the difference between the two remaining black arrows and the newly drawn green arrows. Answer Reflection Questions Erase the lines and labels from the surface of the turntable.

5 Activity 3: Rotation in Three Dimensions Materials (per student group) 1 world globe 1 black dry- erase marker 1 green dry- erase marker 1 turntable with black and green lines drawn from Procedure 1. Obtain the following materials for your group: world globe, a black dry- erase marker, and a green dry- erase marker. 2. Holding the globe with the North Pole at the top and South Pole at the bottom, have one member of your group draw arrows that represent the following air mass movement. Refer to the lines made on the turntable during Activity 2 and the rotation of the earth observed in Activity 1 to predict the movement of the air masses. A. Direction of air mass flowing from the North Pole toward the equator B. Direction of air mass flowing from the South Pole toward the equator C. Direction of air mass flowing from the equator toward the North Pole D. Direction of air mass flowing from the equator toward the South Pole 3. Redraw the arrows on the diagram below. 4. Answer Reflection Questions 1 6.

6 Activity 4: Observing Fluid Convection Materials (per student group) 1 aluminum pie pan (9- in) 2 beakers (100- ml) 1 bottle of food coloring (chilled) water (room- temperature) ice hot water paper towels Put chilled food coloring here Procedure 1. Obtain the following materials for your group: aluminum pie pan, two 100- ml beakers, bottle of chilled food coloring, room- temperature water, ice, hot water, and paper towels. 2. Place a small amount of ice in one of the 100- ml beakers. Fill the beaker with room- temperature water to the 80- ml mark. a. Tip: To make sure that the bottle of food coloring remains chilled, place the bottle in the beaker of ice water while you are preparing the other materials. 3. Pour about 3/4 inch of room- temperature water into the pie pan. 4. Pour 80 ml of hot water into the other 100- ml beaker. 5. Inside the pie pan of water, place the beaker of ice water on one side and the beaker of hot water on the opposite side. 6. Place one or two drops of chilled food coloring in the water of the pie pan at the base of the beaker of ice water. 7. Observe the movement of the food coloring in the water of the pie pan. Answer all the Reflection Questions for this activity.

7 Activity 5: Modeling Storm Systems Materials (per student group) 1 turntable (14- in) 1 aluminum pie pan (9- in) 2 beakers (100- ml) 1 bottle of food coloring (chilled) hot water ice water paper towels Procedure 1. Obtain the following materials for your group: turntable, aluminum pie pan, 100- ml beaker, bottle of chilled food coloring, hot water, ice water, and paper towels. 2. Fill one of the beakers with 80 ml of ice water. Place the bottle of chilled food coloring into the beaker of ice water to keep it cold. 3. Place the pie pan on the turntable. Carefully pour about one- half inch of hot water into the pie pan. a. Tip: Make sure that the water is not too hot, so it will not warp the turntable or cause burns if spilled. 4. Have one group member carefully and slowly rotate the turntable counterclockwise at a constant speed for about one minute. 5. After the turntable and pie pan have been rotating for about one minute, have another group member drop one or two drops of chilled food coloring into the center of the water in the pie pan. Stop manually rotating the turntable and allow it to slow to a stop by itself. Observe the motion of the drops of food coloring in the water and answer the Reflection Questions that follow.

8 Name: Date: Mods: Carolina TM Coriolis Effect and Atmospheric Circulation Kit STUDENT GUIDE Activity Questions Activity 1 Reflection Questions 1. As you looked at the equator while the axis was held vertical, in which direction did the globe rotate, from left to right or right to left? Was this direction of rotation the same for both observers? 2. In which direction (clockwise or counterclockwise) did the globe appear to rotate as you observed the North Pole? In which direction, as you observed the South Pole? Activity 2 Reflection Questions 1. Describe the mark that was made from the edge of the turntable toward the center while the turntable rotated counterclockwise. 2. Describe the mark that was made from the center toward the edge while the turntable rotated counterclockwise. 3. Record the paths of both types of marks on the turntable illustration that follows. Label the illustration with the rotational direction of the turntable.

9 4. Describe the path of the marker itself as observed by the members of your group. 5. If you were viewing the marker from the surface of the turntable as it rotated counterclockwise, how would the marker appear to move? How does this apparent path compare with the path of the marker as observed by your group? 6. Describe the mark that was made from the edge of the turntable toward the center while the turntable rotated clockwise. 7. Describe the mark that was made from the center toward the edge while the turntable rotated clockwise. 8. Record the paths of both types of marks on the turntable illustration that follows. Label the illustration with the rotational direction of the turntable. 9. Describe the path of the marker itself as observed by the members of your group. 10. If you were viewing the marker from the surface of the turntable as it rotated clockwise, how would the marker appear to move? How does this apparent path compare with the path of the marker as observed by your group?

10 Activity 3 Reflection Questions 1. When drawing the lines on the Northern Hemisphere, which turntable model did you reference, and why? 2. When drawing the lines on the Southern Hemisphere, which turntable model did you reference, and why? 3. As air masses move in the Northern Hemisphere, to which direction are they deflected? 4. As air masses move in the Southern Hemisphere, to which direction are they deflected? 5. How might the Coriolis effect influence global air circulation? Activity 4 Reflection Questions 1. Below, record your observations of the food coloring s movement in the water of the pie pan. Be as detailed as possible. 2. Why did the majority of the chilled food coloring initially sink to the bottom of the water in the pie pan? 3. What happened to the food coloring once it reached the beaker of hot water? 4. What type of heat transfer does this model represent?

11 5. Complete the following diagram to explain what happens to the water molecules during this heat exchange. Use arrows to indicate the flow of the water molecules. 6. Knowing that air, like water, moves as a fluid, predict what will happen to air masses as they heat and cool. Activity 5 Reflection Questions 1. In the following diagram, draw your observations of the food coloring s movement in the pie pan while the turntable was rotating counterclockwise. Use arrows to indicate rotational direction. 2. Explain what you observed as the food coloring was dropped into the pie pan. 3. What was the rotational direction of the food coloring? 4. Compare your observations with what is known about the rotation of large storms, such as hurricanes. What similarities did you observe? What differences? 5. What differences do you think you would observe if the turntable were rotating clockwise?

12 6. Given the results from your test in question 5, what would you expect the rotational motion of typhoons in the Southern Hemisphere to be? (Hint: Hurricanes and typhoons form over the warm waters of the tropics and move toward the cooler polar regions.) Assessment 1. Describe and explain how the rotation of a hurricane in the Northern Hemisphere is different from the rotation of a typhoon in the Southern Hemisphere. 2. Look at the diagram below and answer the questions that follow. If a drop of food coloring were placed beside the beaker of hot water, the food coloring would A. sink and move along the bottom of the container toward the cold water. B. move along the top of the water toward the cold water. C. rotate counterclockwise due to the Coriolis effect. D. color the water. The type of heat transfer that is taking place in this illustration is referred to as A. radiation C. convection B. conduction D. cold to hot 3. How does the rotation of the earth affect global air circulation? Examine this simplified diagram of the earth's major wind belts and explain how the Coriolis effect influences the direction of the polar easterlies, the westerlies, and the trade winds. 4. On the basis of the prevailing winds, predict the area most affected by industrial air pollution from Europe. A. eastern United States C. western Asia B. northern Africa D. the Arctic