Meteorology: the study of what goes on in the Earth`s atmosphere

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)
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.