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Air Masses
 Air Mass = large body of air that takes
on characteristics of the area over which
it formed
 Conditions:
 Over land = dry
 Over water = wet
 Polar regions = cold
 Tropical regions = warm
Air Masses
 Types of Air Masses:
 Continental polar (cP) – cold, dry
 Continental tropical (cT) – warm, dry
 Maritime polar (mP) – cold, wet
 Maritime tropical (mT) – warm, wet
 Equatorial – hot
Winds
 When air is heated:



Its density decreases
Warm air rises, produces an area of
low pressure
Cooler denser air produces an area of
high pressure, and moves in under
rising air
Local winds

Sea breeze –during the day solar
radiation warms the land more than
water


air moves inland from the ocean due to air
over land heating up quicker (and is less
dense than the ocean air)
Land breeze –at night when cool air
from land flows seaward

air moves toward the ocean as the land air
cools quicker
Land and Sea Breezes
Fronts
 Air masses move and bump into each other
 Fronts appear at the edges of two air masses
where they are colliding with each other
Fronts
There are 4 types of fronts:
 Cold fronts
 Warm fronts
 Stationary fronts
 Occluded fronts
Cold front
 Occurs when a cold air mass overtakes a
warm air mass
 Cold air forces warm air to rise quickly
 Resulting in strong winds, thunderstorms,
and large amounts of precipitation
Cold fronts usually bring cooler weather, clearing skies, and a sharp change in wind
direction.
Cold Front
Cold Front Diagrams
Warm Fronts
 Occurs when a warm air mass overtakes
a cold air mass
 Warm air slowly rises over the cold air
 Starts with steady rain (8-12 hours) but
eventually clears when temperatures
rise
 Warm fronts tend to move slowly are
far less violent then cold fronts
After warm front passes, weather becomes warm and humid, but generally clear
Warm Front
Warm Front Diagrams
Stationary Front
When neither air mass can move
the other
Similar to warm fronts and can
remain in same place days
Light wind and precipitation occur
across entire region affected
Occluded front
 When a warm air mass gets trapped between two cold
air masses
 Strong winds and heavy precipitation occur