1. Air Masses and Weather Fronts

2. Air masses A body of air with similar characteristics throughout
Humidity and temperature are the two main characteristics used to classify air masses.

3. The “first name” of an air mass describes the humidity of the air mass.
Maritime
– humid (wet) air masses that form over oceans

4. Continental
– drier air masses that form over land

5. The “last name” of the air mass describes the temperature of the air mass.
Polar
- cold air masses out of the north

6. Tropical
- warmer air masses from the south

7. e.g. A Maritime tropical air mass forms over warm ocean water, making the air __________ and __________
moist warm

8. What causes the movement of these air masses?
Prevailing westerly winds push maritime polar air masses from the Pacific onto the west coast, but push maritime polar air masses out to sea on the east coast.

9. Fronts
The area where two air masses meet and don’t mix is called a front. In other words a front is the boundary between two or more air masses.

10. There are 4 types of fronts
Cold Front – Fast moving cold air runs into a slow moving warmer air mass; the cooler air slides under the warmer air and pushes the warmer air upward.

11. Warm Front – Warm air mass collides with a slow moving cold air mass; warm air is less dense and so moves over the cooler air

12. Stationary Front – Cold and Warm air masses meet, without either air mass being moved by the other.
Occluded Front – A warm air mass is caught between two cooler air masses and is lifted above them.