Download 16.2 Air masses & fronts

Chapter 16.2
Air Masses
and
Fronts
Air Masses
• Large body of air where temperature and
moisture content are similar throughout.
• Named for where they form:
M- Maritime- over water- Wet
C- Continental- over land- Dry
P- Polar- over polar regions- Cold
T- Tropical- over tropical regions- Warm
Combine letters to describe air
masses
• mP- Maritime Polar
– Wet, Cold
• cP- Continental Polar
– Dry, Cold
• mT- Maritime Tropical
– Wet, Warm
• cT- Continental Tropical
– Dry, Warm
Air Masses that affect weather in
North America
http://www.physicalgeography.net/fundamentals/7r.html
Air Masses
Fronts
• The boundary between Air Masses
• Four types:
– Cold
– Warm
– Occluded
– Stationary
Cold Front
• Cold, denser air moves under warm, less dense
air and pushes the warm air up.
• Moves quickly and brings heavy precipitation,
followed by cooler, drier air.
http://www.physicalgeography.net/fundamentals/7r.html
Warm Front
• Warm, less dense air moves over cold, denser air.
• Brings drizzly rain, followed by clear, warm weather.
http://www.physicalgeography.net/fundamentals/7r.html
Occluded Front
• Warm air caught between two colder air masses.
• Cold air pushes warm air up, bringing cool
temperatures and large amounts of precipitation.
http://www.physicalgeography.net/fundamentals/7r.html
Stationary Front
• “Stalemate” between a cold air mass and a
warm air mass.
• Brings many days of cloudy, wet weather.
http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/tstorm/stat_front.html
Fronts
Vertical Air Movement
• Cyclone: the winds circulate counterclockwise around a low. The air
is warm at the surface so it rises in a column such that its winds
spiral upward and cool. The cyclone is associated with rain-making
conditions.
• Anticyclone: develops where cold air aloft, being heavier and
having a higher pressure, descends in spiraling motions to reach the
surface as a pressure high. Brings dry, clear weather.
http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html