Weather, Climate and  Change

 Effect of Rotation of Earth on Oceans and Atmosphere

OBJECTIVES:

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Exploring the movement of oceans and atmosphere.
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Discovering Coriolis motion.

VOCABULARY:
·         Coriolis Motion
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ocean
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atmosphere
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rotation

MATERIALS:
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small wax cup
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circle cut from construction paper
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Small nail
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Water bottle with dropper
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Ping pong ball
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Straw
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Powerpoint “Oceans and Atmosphere”

VIDEOS

1. The Coriolis effect (MIT demonstration)

2.  Coriolis effect (Coriolis effect on weather) https://www.youtube.com/watch?v=i2mec3vgeaI

BACKGROUND:

The rotation of the Earth on its axis causes what is called the Coriolis Motion.  (The name comes from a 19th-century French engineer-mathematician Gustave-Gaspard Coriolis in 1835.)  The Coriolis Motion is a major overlay on the pattern, and this has to do with deflection of particles because of this motion. The earth's rotation affects the oceans and the atmosphere.  The classic example that you can perform with your children is to have them throw a ball to a person when they are on merry-go-round.  The ball will be thrown straight, but will appear to be deflected to the people on the merry-go round.  This is an analog to the movement of water in our oceans.  In the northern hemisphere this deflection is to the right and in the southern hemisphere this deflection is to the left.

The rotation of the Earth affects the outer portions of the Earth.  The effect on the oceans is a steady and continuous reaction, which causes the general direction of the ocean's motion.  This is called the Coriolis Motion causes the Coriolis Effect, whereby water is deflected to the right in the Northern Hemisphere and deflected to the left in the Southern Hemisphere.  Many times the words are used interchangeably.  The Coriolis Motion is a difficult phenomenon to fully understand, but it is important for children to realize the influence of a rotating sphere on the motion in the ocean and  ocean currents.

If you would like to see this motion, look at the following UTube from MIT.

The atmosphere also moves because of this rotation as seen in wind patterns. There is a difference between local and general worldwide winds. General winds include those that stretch thousands of miles over the Earth's surface with almost permanent directional patterns. Local winds are characteristic of particular geographical regions and exert a pronounced influence on the local climate.

The pattern of the general wind circulation is primarily determined by the unequal heating of the atmosphere at different latitudes and altitudes and by the effects of the Earth's rotation. The general wind pattern includes doldrums, jet stream, polar easterlies, trade winds, and westerly winds.

There are also other reasons that you have to consider for motion of the oceans and atmosphere.  If you would like more information please go to the following link :

click on the units under Water Science

These readers can help you understand the material better.  It is complicated, but these units help the children begin to understand this motion.

PROCEDURE:

1.    Movement on Earth is very difficult to understand, especially when children think that when they stop, there is no movement.  Wrong!  Ask the children to think of themselves as Martians, looking at the Earth through their spaceship. If you have an inflatable or solid globe, show it rotating on its axis.

As the Martians look at this blue planet called Earth, they notice that polar bears and penguins look like they are standing still (acting cool), but people especially those that live near the equator are moving around very quickly, about 1000 miles per hour!  But do the people feel like they are moving that fast?  Of course not, but the Earth is moving along its axis, a particle near the axis moves slower than a particle along the equator, which has a longer distance to travel.    Hence, the Martian would see polar bears (who live only near the north pole) and penguins  who live only near the south pole) as moving very slowly.

This movement causes motion on the crust of the Earth, but because the ocean is a liquid and the atmosphere is a gas, they responds quicker than the solid Earth and one of the main reasons we have ocean and wind currents.

2.    Use the powerpoint presentation on  “Oceans and Atmosphere” and go over the main points of rotation and solar radiation that drives the surface ocean and atmospheric movements.

3.    First activity is to prove that motion can cause a deflection and it is different if you are moving clockwise or counterclockwise.

EXERCISE I.
ocean movement on a spinning planet

1. Hand out small earth balls and worksheet.  Have them follow the instructions to figure out which was the earth appears to move (to right or left) from the perspective of the north or south pole and fill in worksheet.

2.    Use the powerpoint presentation on “Oceans and Atmosphere” and go over the main points of rotation and solar radiation that drives the surface ocean and atmospheric movements (slides 1-6).

3.  Play the two videos.  The first shows the effect by throwing a ball.  The second goes over the principal on a global scale and how it affects weather.

Ask the students to make a prediction as to what direction they think the ocean currents will move in the northern and southern hemisphere

1.    Place small wax cup down.

2.    Place a piece of heavy construction paper on small end.

3.    Firmly place nail or pin through center of construction paper (being careful not to allow nail head to come through).

4.    Push nail through the bottom of the cup so paper can spin on the tail on top of the cup.  Turn nail upside down (head facing table) and spin like a top with the construction   paper spinning on top of cup.

5.    Fill medicine dropper with water

6.    One partner should spin the construction paper right to left.  As the construction paper is spinning, the second partner will drop 1-3 drops of water   as close to the nail as possible.  They will see curved tracks from the center.  They should enter what this looks like on their worksheet.

Ask the students to make a predition as to what direction they think the ocean currents will move in the northern and southern hemishphere.

1.    Place small wax cup down.

2.    Place a piece of heavy construction paper on small end.

3.    Firmly place nail or pin through center of construction paper (being careful not to  allow nail head to come through).

4.     Turn nail upside down (head facing table) and spin like a top with the construction   paper spinning on top of cup.

5.    Fill medicine dropper with water

6.    As the construction paper is spinning, the second partner will drop 1-3 drops of water   as close to the nail as possible.

Have the students change the direction of the spin and record what happens.  This demonstrates that a moving "sphere" deflects particles because of the motion.  This is the same thing on the Earth, except the water can't just "fly" off.  (Because of other forces like Centripetal Force.).

Below a projectile that is thrown toward north (and person is facing north) it deflects to the right.   In B the projectile is thrown to the south and person is facing south, it deflects to the left.
 Deflection of a particles in northern (A) and southern (B) hemisphere Keeping a ping-pong ball suspensed

EXERCISE  II.  The power of air movement--wind currents

1. Give 2 students small paper cup, a bendy straw and medium puff ball.  Cut the end of the bendy part off so it is just above the bend.  Make a small hole in the middle of the bottom of the cup so that the straw will fit snuggly.  (See photos).  Blow in the straw and the puff ball will float and spin above the bottom of the cup.  Have students see how well they can keep the puff ball in the air without it going out of the cup.

The puff ball should seem like it is floating, but gravity is pushing it down and the air is pushing it upwards.

This activity shows that wind currents can be strong enough to life things. (This is referred to as Bernoulli’s Principle.)

2    Next,  have students play “soccer ping pong.”   Put the ping pong ball in the center between them and have them try to blow it in the others side.  Put obstacles between them and have them direct the power of the wind.  Discuss with them that wind cannot go through things, so you have to blow at the right angle to move the ball.  This is similar to what happens on Earth.  Air goes up mountains, around houses, and down steep slopes causing the  wind to go slower or faster.  There are many reasons for this, but the activity is just trying to get children to see that wind is a force.

3.  Make a small tent with heavy paper see if they can get the ping pong ball to go up the sides; ask students to find different ways to move the ball and share their discoveries at the end. Can they get the wind to go over the “mountains”?

4.  If here is time you can let them try to move the ping pong ball using straws to blow with.  They will get more power on the ping pong ball since the wind is more controlled.  This gives the idea of different wind strengths.