Abstract
Where toxicants of environmental health importance are transported through the air, understanding the natural processes which contribute to air movement and weather patterns of a region is important.  For example, in some cities inversion layers trap pollutants close to the ground. Students will examine physical characteristics of several types of air masses. Students will discover air masses can be identified and defined by their temperature and moisture content.

Objectives
Students will be able to:
1. Categorize air bodies by temperature and moisture characteristics on given maps.
2. Recognize large regions of similar type air on given maps.
3. Describe similarities and differences between air temperatures on the given map,
Describe similarities and differences between dew point temperatures on the given map.

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,
  • atmosphere as carbon dioxide gas,
  • water as dissolved carbon dioxide, and
  • all organisms as complex molecules which control the chemistry of life

Teacher Background
When a large body of air remains over an area for several days or weeks, the body of air may change its’ thermal and moisture properties according to the land or water under it.  The air exchanges heat with the land or water, either warming or cooling, until it’s’ temperature closely matches the surface below.  The body of air also gains or loses moisture depending on the temperature and surface moisture content.  A body of air resembling characteristics of the surface under it is called an air mass.

Related and Resource Websites
http://k12.ocs.ou.edu/teachers/lessons/airmasses.html
Air Masses Scaffolding Activity: http://ww2010.atmos.uiuc.edu/(Gh)/guides/crclm/act/arms.rxml
Article on USA Today on Air Masses: http://www.usatoday.com/weather/tg/wamsorce/wamsorce.htm
Online Guide on Air Masses & Fronts: http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/af/home.rxml
Oklahoma Meteorology on Air Masses: http://okfirst.ocs.ou.edu/train/meteorology/AirMasses.html
Geography 101: The Physical Environment on Air Masses & Fronts: http://www.uwsp.edu/geo/faculty/ritter/geog101/uwsp_lectures/lecture_fronts.html

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Activity
1. Select maps for your state.  Maps should show two different air masses within the state. A good example is when a cold front is moving across the state, preferably with continental polar and maritime tropical air masses. (If unavailable, Oklahoma maps are available at the addresses listed in the materials section)

2. Divide the class into groups of 3 or 4 students.

3. Distribute Protocol Sheets and allow students time to complete as you walk around assisting.

4. When the students circle the warm, cool, moist, and dry regions, be sure they do not use small circles around only a few stations. Try to get them to see a large region (e.g., ½  or ¼  of the state) as warm or cool, moist or dry.

Provide students with the following
PROCEDURE

1. Obtain one temperature map and one dew-point temperature map for each student in your group.

2. Contour the temperature map and dew point map every 10 degrees.

3. Circle the region on your map containing the warmest temperature readings. Use a red pencil.

4. Circle the region on your map containing the coolest temperature readings. Use a blue pencil.

5. Circle the region on your map,  containing the highest dewpoint temperatures. Use a green pencil.

6. Circle the region on your map containing the lowest dew point temperatures. Use a brown pencil.

QUESTIONS

1. Where are the warmest temperatures? Are the dew points high or low in this region? Label this region A.

2. Where are the coolest temperatures? Are the dew points high or low in this region? Label this region B.

3. If you were to describe the regions as "warm and dry", "warm and moist", "cool and dry", or "cool and moist", how would you describe region A? Region B?

4. The Northern Hemisphere can be divided into three "latitudinal" regions:

a. the polar region, between 0°N and 30°N,
b. the middle latitudes, between 30°N and 60°N, and
c. the tropics, between 60°N and 90°N.

* Where do you think the air in region A came from? Why? Region B? Why?

5. What do you think causes air to be moist or dry? Why?

6. How specific can you get predicting where a region of air is originally from?

7. How can you predict these regions? What does this say about how "air masses" are formed?

8. Based on our class data and discussions, what can you say about the source and characteristics of the air which covers large state regions?

Embedded Assessment
Can students categorize air masses by temperature and moisture?  Can students recognize similarities and differences between temperatures and dew points?

The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

Supported by NIEHS grant # ES06694