Download Name: Mr. Schwartz Period: ______ Date: Earth Science /20 Air

Name: ___________________________________
Period:
___________
Date: ___________________
Mr. Schwartz
Earth Science
/20
Air Masses and Fronts
Here is an opportunity to tie together what we have learned about how air masses move over the Earth. Work
on this activity with your partner. You may have to refer to your text or homework sheets.
Above is a map of a newly discovered continent ruled by the Evil Supreme Schwartz. Any resemblance to a
chicken is intentional.
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Air is spiraling outward from the 4 high-pressure centers marked with an H.
1. Draw arrows to show the air spiraling out from the highs (clockwise or counterclockwise?). Why does the air
spiral?
As air travels over the surface, it will acquire the moisture characteristics of the surface. Air traveling over land
stays dry; air traveling over the ocean will become moist.
2. Label the air near each high as moist or dry. Why does the air from a high start out dry?
As air travels over the surface, it will acquire the temperature characteristics of the surface. Air traveling over
cold northern areas cools off; air traveling over warm southern areas will become warm.
3. Label the air near each high as cold or warm. What heat transfer processes are at work to change the air
temperature?
An air mass is a large "blob" of air with similar characteristics throughout. Air masses are named according to
their moisture and temperature characteristics.
4. Label the moist air "maritime", the dry air "continental".
5. Label the cold air "Polar", the warm air "Tropical".
You should now have four different air masses: continental Polar, continental Tropical, maritime Polar,
maritime Tropical. On weather maps, the abbreviations cP, cT, mP, mT are used. The first letter of each
abbreviation is not capitalized to avoid confusion with other abbreviations.
6. Label the map with the air mass abbreviations.
Fronts are the boundaries between air masses, marking the edges of individual air masses.
7. Draw solid lines where the air from different air masses meets. Only use the 3 high pressure areas above
30° North
Prevailing winds cause air masses and the fronts that form between them to move. If warm air replaces cold air,
it is called a warm front. If cold air replaces warm air, it is called a cold front. Remember that the winds
between 30°N and 60° N are called the “prevailing westerlies”.
8. What causes the prevailing winds? Draw arrows on the map to show their direction.
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9. Label the cold fronts with little triangles sticking out of the front in the direction the front is traveling. Label
warm fronts with little half circles on the side of the line. The symbols indicate front direction on weather maps.
When fronts move, warm air always rides up over colder denser air. As the warm air rises, its temperature
drops, so relative humidity increases.
10. Why does relative humidity increase when temperature decreases?
11. What will form along the fronts if the temperature of the warm air drops enough to reach its dew point?
Draw this on the map.
In the temperate middle climates, air that rises in fronts contributes to the global circulation of air back toward
the poles and equator along the top of the troposphere. Adding to this same circulation is the air that rises in
low-pressure centers. These lows usually form where fronts join together.
12. Draw a low on the map and the wind spiraling into it (clockwise or counterclockwise?).
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