11/9 Wind Patterns - Ryan Beeler | Library

Read the section below and answer questions 1-11

An air mass is a body of air that is characterized by a particular temperature and humidity. Air masses usually cover hundreds of thousands of square miles and have temperatures and humidities similar to the area where they originate. Polar air masses are those originating between the Arctic Circle and the North Pole or between the Antarctic Circle and the South Pole; they are characteristically cold. Tropical air masses are those originating between the Tropic of Cancer and the Tropic of Capricorn; they are warm air masses. Maritime air masses form over the ocean; they are very moist. Continental air masses, as their name implies, form over land; they often to contain less moisture than maritime air masses.

As air molecules are heated, they gain energy and move apart from one another, increasing the volume of the air mass and decreasing its density. As its density decreases, the air mass rises. When air molecules cool, they move closer together, increasing in density, and the air mass sinks.  When the air in the atmosphere cools and becomes dense, it sinks toward a source of heat, becomes warmer and less dense, then rises and moves away from the heat source, in a circular motion – this is called a convection current. Remember, it is the differing density of air masses (due to temperature) that leads to convection currents in the atmosphere.

1

What is the difference between polar air masses and tropical air masses?

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What is the difference between continental air masses and marine air masses?

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What happens to an air masses density and movement as is it heated?

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What happens to an air masses density and movement as it is cooled?

Activity 1: Convection
Place the vial on a hot plate set on its lowest heat setting.
As the convection fluid heats up, observe the currents in the fluid.
Answer the questions for Activity 1.

1

What happens to the convection fluid as it heats up?

1

What do you expect will occur as air masses move over cold locations?

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What do you expect will occur as air masses move over hot locations?

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What type or types of air masses originate from near the equator?

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Which type of air mass, continental or marine, would have more moisture?

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What climate would regions where air masses from the equator and the poles collide probably have?

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Where would you expect to find these regions?

Read the section below and answer questions 12-14

The Coriolis Effect occurs when a moving object, including air masses, appear to be deflected to the right or left of their path when traveling over a rotating body – like the Earth. The amount of deflection is determined by both the speed and latitude of the moving object. The greater the speed, the greater the deflection force exerted on the object.

How does this force relate to the other mechanisms that affect the global climate? Consider that, in the absence of other forces, wind moving in a straight line at a certain speed will continue to do so. However, because the Earth’s surface moves more quickly at the equator than it does at the poles, winds in the Northern Hemisphere are deflected to the right, and winds in the Southern Hemisphere are deflected to the left. The Coriolis force not only affects the path of large air masses, but it also affects the rotation of large storm systems including hurricanes and typhoons, as well as the movement of ocean currents.

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What is the Coriolis Effect?

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Because of the Coriolis Effect, winds in the Northern Hemisphere are deflected in what direction?

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Because of the Coriolis Effect, winds in the Southern Hemisphere are deflected in what direction?

Procedure



Note: Move the pen across the surface of the globe at the same speed in each step of this activity.

Have one partner hold the globe while another partner uses the marker to draw a line on the globe from the North Pole to the equator.
Have one partner hold the globe and rotate it counterclockwise as viewed from the North Pole, as shown in the figure. While the globe is rotating, have another partner use the wet-erase marker to draw a single line form the North Pole to the Arctic Circle, then back from the Arctic Circle to the North Pole.
Continue to rotate the globe counterclockwise while one partner draws a single line from the Arctic Circle to the Tropic of Cancer, then back to the Arctic Circle.
Continue to rotate the globe counterclockwise while one partner draws a single line from the Tropic Cancer to the equator, then back to the Tropic of Cancer.
Continue to rotate the globe counterclockwise while one partner draws a single line from the equator to the Tropic of Capricorn, then back to the equator.
Continue to rotate the globe counterclockwise while one partner draws a single line from the Tropic of Capricorn to the Antarctic Circle, then back to the Tropic of Capricorn.
Continue to rotate the globe counterclockwise while one partner draws a single line from the Antarctic Circle to the South Pole, then back to the Antarctic Circle.
Study the lines drawn on the globe, and then answer the questions for Activity 2

1

As the globe rotated counterclockwise, what happened to the line that was being drawn, observed from a point above the North Pole? (did it stay straight, move right, move left, ect)

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Based on your observations, how does the Earth’s clockwise rotation affect the movement of air masses in the Northern AND Southern hemisphere? (More than one)

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Although it is near the Atlantic Ocean, the northwest coast of Africa is characterized by hot, dry deserts. Using your knowledge of the Coriolis Effect and the picture provided, explain why this is true.