Activity 14.11 Factor Affecting Wind Direction: The Coriolis Effect To better un
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Activity 14.11 Factor Affecting Wind Direction: The Coriolis Effect
To better understand how the Coriolis effect influences the motion of objects as they move across Earth’s surface, conduct the following experiment:
Step 1. Working in groups of two or more, construct a rotating “table” that represents Earth’s surface by first taping a thumbtack upside down on the table top (or inserting it through a piece of cardboard). Next, center a sheet of heavy-weight paper or thin cardboard over the point of the tack and push the sharp end of the tack through the paper (Figure 14.13 ). Turning the paper about the thumbtack represents the rotating Earth viewed from above the pole.
Figure 14.13
Coriolis effect experiment setup—Southern Hemisphere.
Step 2. Place a straight edge (or a 12-inch ruler) across the paper, resting it on the sharp point of the thumbtack.
Step 3. Using the straight edge as a guide and beginning at the edge nearest you, draw a straight line across the entire piece of paper. Mark the beginning of the line you drew with an arrow pointing in the direction the pencil moved. Label the line “no rotation.”
Step 4. Have one person hold the straight edge and another person turn the paper counterclockwise (the direction the Earth rotates when viewed from above the North Pole) about the thumbtack. Next, while spinning the paper at a slow, constant rate, draw a second line along the ruler, using a different-color pencil. Mark the beginning of the line you drew with an arrow pointing in the direction the pencil moved. Label the resulting line “Northern Hemisphere.”
Step 5. Repeat step 4, but this time rotate the paper clockwise (representing the Southern Hemisphere). Label the resulting line “Southern Hemisphere.”
Step 6. Repeat step 4 three more times, varying the speed of rotation of the paper with each trial. Identify each new line by labeling it either “slow,” “fast,” or “very fast.”
In the Northern Hemisphere, is the apparent path of a free-moving object deflected to the right or left? In the Southern Hemisphere, is the deflection to the right or left?
Northern Hemisphere:
Southern Hemisphere:
Summarize your observations regarding the rate of rotation and the magnitude of the Coriolis effect you observed in step 6.
Considering what you have learned about the Coriolis effect, briefly describe the Coriolis effect on the atmosphere of the planet Venus, which is about the same size as Earth but has a period of rotation of 244 Earth days.
Compare the strength of the Coriolis effect on Jupiter with that on Earth. (Note: Jupiter is a planet much larger than Earth, with a 10-hour period of rotation.)
To summarize, examine surface wind directions associated with high- and low-pressure cells in both hemispheres by combining your understanding of pressure gradient and Coriolis effect. Refer to Figure 14.14 . The concentric circles represent isobars. Add arrows to show the winds. The diagram for a low-pressure cell in the Northern Hemisphere is already completed. Complete the other three pressure cells with arrows that show the wind patterns.
Figure 14.14
Northern and Southern Hemisphere high- and low-pressure cells.
In the following spaces, indicate the movement of air associated with high- and low-pressure cells in each hemisphere. Write one of the two choices given in italics for each blank.
NORTHERN HEMISPHERE HIGH LOW Surface air moves into or out of Surface air motion is clockwise or counterclockwise SOUTHERN HEMISPHERE HIGH LOW Surface air moves into or out of Surface air motion is clockwise or counterclockwiseExplanation / Answer
a) Coriolis effect is an inertial force due to which the wind deflected to the left in the Northern Hemisphere and to the right in the Sothern hemisphere. The two main reasons for this effect are - 1. the eastward rotation of Earth and 2. the tangential velocity of a point on the Earth due to a function of latitude . The velocity is maximum at the equator and minimum at the poles. So the coriolis deflection is associated with the motion of object, motion of Earth and the latitude.
b) Venus has the same size as the Earth. Venus's atmosphere is very dense. The coriolis effect is very weak here because of the very slow rotation of Venus.
c) Jupiter is a planet much larger than the Earth. Jupiter shows a very large coriolis effect due to its rapid rotation. The banded appearance of the Jupiter is created due to this effect. Because of the strong deflection of wind a hurricane-force gales is created in jovian atmossphere and as it blows east-west forming the banded appearance which is absent in the Earth.
d) In the Northern hemisphere,
Surface air moves from low pressure to high pressure zone.
Suface air motion is clockwise
In the Southern Hemisphere,
Surface air moves from high pressure to low pressure zone.
Surface air motion is counterlockwise.
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