Download Atmospheric Cells

Atmospheric Cells
Author: Kirstin A. Bittel
Time:
1 period
Preparation
5 minutes making overheads
Time:
Materials:
Overhead One (pg.1) - atmospheric cell and solar radiation
Overhead Two (pg.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.
http://pulse.pharmacy.arizona.edu/9th_grade/from_global/earth_science/atmos_cells.html
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
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].
http://pulse.pharmacy.arizona.edu/9th_grade/from_global/earth_science/atmos_cells.html
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?
http://pulse.pharmacy.arizona.edu/9th_grade/from_global/earth_science/atmos_cells.html