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Atmospheric Cells

By: Kirstin A. Bittel


Time:
1 period
Preparation Time:
5 minutes making overheads
Materials:
Overhead One (pg.1 of 2) - atmospheric cell and solar radiation
Overhead Two (pg.2 of 2) - Detail of atmospheric cells

Abstract
In this lesson, students will explore the idea of the sun as a central force in the development of atmospheric convection cells.

Purpose – Explanation of processes that drive world wind patterns.

Objectives
Students will be able to:

1. Recognize that the sun is the source of energy driving atmospheric cells.
2. Relate the motion of the atmospheric cells to mantle convection cells.
3. Recognize that the function of atmospheric cells is to move heat from warm     areas to cooler ones. (The jet stream is one specific example.)
4. Recognize that air flows from high-pressure zones to low pressure zones.

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
Great information on the cause of wind is available at:
http://www.weatherquestions.com/What_causes_wind.htm

Specific information on the Winds and cells is available at:
http://web.clas.ufl.edu/users/mrosenme/Oceanography/Lectures/atmospheric_circulation.htm

More detailed information available from Climate Change:
http://calspace.ucsd.edu/virtualmuseum/climatechange1/07_1.shtml

More great information is available at USA Today Weather Basics: http://www.usatoday.com/weather/resources/basics/wworks0.htm

Atmospheric Circulation

Image Courtesy of The Remote Sensing Tutorial
ATMOSPHERIC CIRCULATION; WEATHER SYSTEMS, by NASA.



 

 

 

 

 

 

 

 

 

 

 


Activity
1. As students enter the room, have the following question written on the board: What do you think might cause the global wind belts we observed yesterday?

2. Allow students about 5 minutes to record their thoughts and another 5-10 minutes to share their thoughts and their rationale. If the class seems stumped by the question, prompt them to think about other systems on the earth that move from place to place. Hopefully one student will bring up the idea of convection as a way to move air masses around the globe.

3. Show students Overhead One which shows the Earth and the wind belts and atmospheric cells. Cover the lower half of the overhead for now. Ask students to make observations about the cells. What patterns do they notice? [This should remind them of convection cells, the way the atmospheric cells meet and converge either pulling air down or pushing it up.)

4. Draw students’ attention to the equatorial region. In which direction does the air move? [Up] What would cause the air to rise? Hopefully students will say heat immediately. If not, ask them how a balloon, specifically one that carries people, rises. Guide students via questioning to explain that once the hot air (which is less dense) has risen into the upper atmosphere, cools (becomes more dense) and then sinks. Ask students to look at the map and estimate where they think the majority of this air sinks into (the air sinks at about the 30tth parallel. This area is called the Horse Latitudes because the winds are not very strong in this area .Sailors would get stuck and throw their horses overboard to lighten the load of the ship so that lighter winds could carry the ship.)

5. What do they notice at the 30th parallel? [Air sinks] 60th parallel [Air rises] Polar region? [Air sinks]

6. Draw students’ attention to the wind belts at the equator, 30th parallels, 60th parallels, and Polar Regions. What types of pressure zones exist there? [In order, there are low, high, low, and high-pressure zones.] Is there a relationship between the type of pressure and the direction of the air current? [Low-pressure zones exist where air rises and high-pressure zones exist where air sinks].

7. What do students think causes these convection cells? [Heat from the sun]. Reveal the lower half of the overhead at this time. Where do the solar rays strike the Earth? How does this relate to the rising and sinking of air on the Earth? [Air rises where it is warmed by the sun and sinks where it is not].

8. Reveal Overhead Two showing the names of the cells and more specific airflow. Tell students the Hadley Cell is named for George Hadley who discovered the mechanism for the easterly motion of the Trade Winds in 1735. Edmond Halley though, did attempt to explain the process in 1686.The Ferrell Cell is named for William Ferrell who explained and noted the motion of the Westerlies in the 1800s.

9. Direct students to estimate how the pressure zones affect wind flow. Does the wind flow from low pressure to high pressure or high pressure to low pressure? [High to low].

10. What do students notice about the type of air that rises and the type that falls? Why does this happen? [Warm, moist air rises, the rains fall as the air cools so that only dry air is left to fall].

11. Show students the map of the jet stream at http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cyc/upa/jet.rxml and at
http://www.john-daly.com/guests/jet.htm. Tell students this air flow actually pushes warm air up into Europe and keeps the temperatures warm there, especially when the jet stream winds are slower.


Closure
How do students think this movement of cold and warm, wet and dry air, high and low pressure zones affects weather in different countries? What do these cells do to the overall temperature of the Earth? How might these patterns help us determine where pollutants from one country are likely to travel?

Embedded Assessment
Do students recognize that the sun causes the heating of the air and the resulting currents? Do they understand the similarities between mantle convection and atmospheric convections? Do they also understand that the cells move warm air in order for them to see the relationship between pressure and the winds?

 

 

 

 

 

 

 

 

 

 

 

 


 


PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:


an
NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

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Supported by NIEHS grant # ES06694


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