1. Air Masses
Investigation 9 Part 1

2. STAGNANT AIR
Sometimes a large mass of air stays over a portion of Earth’s surface for a long time and doesn’t move. Meteorologists call this stagnant air.
Stagnant air can form over any part of the earth, but usually forms over areas with uniform surfaces with few mountains. These areas are called source regions.

3. AIR MASSES
Meteorologists have a word for these large bodies of air that stagnate over Earth’s surfaceair masses
Air Masses are large, thick bodies of air that are uniform in temperature and humidity.
4 types of air masses, can be combined: Continental, Polar, Tropical, and Maritime.
Gulf of Mexico: Maritime Tropical
Canada: Continental Polar

4. Fronts
When two air masses meet, a boundary forms between them. There is little mixing between the two air masses.
The boundary between the air masses is called a front.
Called a front because it looks like two opposing forces clashing on a battlefront during WWI

5. FRONTS
Cold Fronts occur when a cold air mass overtakes a warm air mass
When a warm air mass overtakes a cold air mass, the boundary is called a warm front.