Section 12-1:
The Causes of Weather
Meteorology: the study of what goes on in the
Earth’s atmosphere
Weather vs. Climate:
Weather: the current state of the atmosphere in an
area, or short-term changes in the atmosphere.
Climate: long-term variations in weather for a
particular area. Climate is usually averaged over the
course of 30 years or more.
air masses: a large body of air that takes on the
characteristics of the area over which it forms, such
as the amount of moisture or temperature.
- Air masses form over land or water
- Those that form over land have less exposure to
moisture, so they are drier than those that form
over water.
Types of air masses: Figure 12-3, page 303
Warm and dry continental tropic (cT)
Warm and humid maritime tropic (mT)
Cold and dry continental polar (cP)
Cold and humid maritime polar (mP)
Artic (A)
All 5 of these air masses can be found in North
America because of the closeness to the source
regions associated with each air mass. (see figure 123)
Examples:
Maritime tropical (mT) air masses form over tropical
oceans such as the Carribean Sea and the Gulf of
Mexico. It brings hot, humid weather to the eastern
2/3 of the U.S.
Continental polar air (cP) forms over Canada and
Alaska and makes for very cold winters when the
nights are long.