Download Chapter 12 - Weather

Shuddle and Atmosphere
Lego Shuttle
reached an altitude
of 35,000 meters.
Which layers of the
atmosphere did the
shuttle reach before
descending back to
Earth’s surface?
Chapter 20 - Weather
 Objectives:
 -Identify factors that
determine the
characteristics of an
air mass
 -Compare and
contrast different
types of air masses
Layer of Atmosphere
Air masses
Large body of air in the lower troposphere
that has similar characteristics
(temperature, humidity) throughout.
Several thousand km in diameter
Characteristics depends on where the air
mass originated
Air Masses Continued…
As air masses move they take with it the
temperature and humidity with them
For example: As an air mass from Canada
moves south, Milwaukee, WI will become
cold and dry
Types of Air Masses
Continental Arctic (cA)
Continental Polar (cP)
Maritime Polar (mP)
Maritime Tropical (mT)
Continental Tropical (cT)
Continental Arctic (cA)
Originate in arctic regions
Extremely cold air which causes cold
waves
Very dry air masses
Continental Polar (cP)
Originate over inland regions of Alaska
and Canada
Somewhat warmer than cA air masses
If cP air masses pass over the Great Lakes,
they can pick up moisture
Results in Lake-Effect snow
Maritime Polar (mP)
Originate over the ocean in high latitudes
Cold and Damp air
If mP cools to its dew point, fog, clouds, or
precipitation results
mP air from North Atlantic can bring
heavy snow storms called nor’easters
Maritime Tropical (mT)
Originate over warm tropical oceans
Warm and moist air
Brings humidity to Midwestern and
Eastern United States
Thunderstorms can develop as a result
Continental Tropical (cT)
Originate over deserts
cT air masses are hot (can exceed temps
over 100 degrees F.) and dry