1. Air masses and fronts
1. An air mass is a wide-spread section of the troposphere with uniform temperature and humidity (moisture)
2. The source region is the geographic location the air mass developed over.
If air settles over one location for a long time, it develops the characteristic temperature and moisture of the area.
Uwsp.edu

2. Oceans (maritime) carry a lot of water vapor
Because temperature changes so much with latitude, tropical areas are warm and polar are cold.
Oceans (maritime) carry a lot of water vapor
On land, (continental) there is little water and the air is dry.
blueollie.wordpress.com

3. Page 13 ESRT uses symbols for the air masses
Dry air is small ‘cf’ or continental
Moist air is small ‘m’ for maritime
Cold air is ‘P’ for Polar and REALLY cold air is ‘A’ for arctic.
Warm air is ‘T’ for tropical
Geography.hunter.cuny.edu

4. And to practice:
2. The characteristics of the air mass is due to the __________________ region, or area where it formed. For each of the following locations create our ______ _________ (and weather), identify the characteristics of the air, using the terms continental, maritime, tropical, arctic and polar.
Gulf of Mexico:
Central Mexico:
Great Plains (winter):
Central Canada:
Northern Atlantic:
1. Bringing those two characteristics together, the air masses may be described. For the following, identify the characteristics:
cT:
mT:
cP:
mP:
cA:
Review book Chapter 8 pages
Air masses and polar fronts:
for air masses

5. Fronts: the boundary between two air masses
A boundary describes where two different things meet.
Between countries
Between lawns
Between air and land.
A frontal boundary is where two different air masses meet. Energy is exchanged.
Fronts bring a change in weather.
One type of air mass pushes in and replaces another one.
“Bad weather” (storms and precipitation) occurs at fronts.

6. How severe the storm is depends on:
how quick the change is
The differences between the 2 air masses:
a REALLY warm, moist air mass meeting a REALLY cold, dry air mass will produce dramatic weather/storm.
How much moisture is in the warm air mass.
weather.thefuntimesguide.com

7. Page 13 of ESRT lists 4 types of front and symbols
The type of front created depends on the direction the air masses move and the way the air masses meet.
In the US, our weather systems tends to move from west to east.
The winds in a storm, tend to make a counterclockwise rotation.
Page 13 of ESRT lists 4 types of front and symbols
scoutweatherbadge.wordpress.com

8. Cold Fronts
Side view:
physicalgeography.net
geography.hunter.cuny.edu

9. Cold front overview
Cold front, in which heavy cold air replaces light, warm air .
The effect is tall, dramatic cumulonimbus clouds, lots of wind, and brief and intense precipitation. (hail, t-storms and even tornadoes)

10. Precipitation happens at the front
Clouds form at fronts because warm, moist air is pushed up at the boundary by the heavier, colder air mass.
Clouds form as rising air cools to the dew point temperature and water vapor condenses around condensation nuclei, such as soot or ash.
Precipitation happens at the front
explore.ecb.org

11. Warm front: side view nauticed.org

12. Warm front: map overview
Warm front, in which warmer air replaces colder air. The effect is cirrus and stratus clouds, steady precipitation that may last for a day or two.
Usually, the warm air has more moisture.
The warm air is pushed up at the frontal boundary, causing clouds to form.
gcel.com.mx

13. Precipitation happens ahead of the front.
The wedge-shape front is caused by the warm air slowly pushing up along the boundary.
Precipitation happens ahead of the front.

14. Occluded front: side view
physicalgeography.net
aos.wisc.edu

15. allposters.com
Occluded front, in which a cold air mass wraps around a warm air mass, actually lifting the air off the ground.
This causes a REALLY dramatic change in weather, intense winds and violent precipitation. (Nor-easters, some tornadoes and t-storms)

16. Overview muhs.acsu.k12.vt.us

17. Stationary front lewistonpublicschools.org

18. Rising air expands and COOLS. Water vapor CONDENSES.
Stationary fronts may last for days because the 2 air masses just don’t really move. Usually, the characteristics are similar to the warm front, just prolonged.
Again, it is the warmer air that is pushed up because it is less dense.
Why clouds???
Rising air expands and COOLS.
Water vapor CONDENSES.

20. Previous page: Polar front development
Review book chapter 8 pages and questions
for fronts