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Air Masses and Fronts
 Air Mass: Large section of
the troposphere
 uniform temperature
 Uniform humidity
As air masses move
from one area to
another they bring
changes in the
temperature
Changes in the


Two Categories of Air
Masses
Maritime: Air mass
that originates over
the ocean and has
a.
Dry air
b.
Moist air
Continental: Air
mass that originates
of land and has
a.
Dry air
b.
Moist air
The Four Kinds of Air Masses
Maritime Tropical (mT)
 Originates in the tropics
 Warm and humid
Continental Tropical (cT)
 Originates in tropical land masses
 Hot and dry
Continental Polar (cP)
 Originates of high altitude land areas
(Canada)
 Dry and cold
Maritime Polar (mP)
 Originates over cold polar ocean (Gulf of
Alaska)
 Cold and humid
Weather in CA

Which type of air mass controls our weather?
A.
Continental Tropical
B.
Continental Polar
C.
Maritime Polar
D.
Maritime Tropical
Weather in CA
C. Dominated by
Maritime Polar (mP)
 Originates over cold
polar ocean (Gulf of
Alaska)
 Cold and humid
Fronts

Front: a boundary between two air masses
Warm air always rises over cool air
 Fronts are associated with stormy conditions

Cold Front
 A cold front: the transition zone where a cold air mass is
replacing a warmer air mass.
 Associated with
a. low pressure
b. High pressure
c. No pressure
Cold Front- draw this
Cold Front
1.
the cold air mass meets warmer air mass ahead of it
2.
The less dense warm air rises & cools
3.
water vapor condenses & clouds form
Cold Front
 Which of these symbols represents a cold
front on a weather map?
A
B
C
Cold Front


As air moves vertically at a cold
front, what type of clouds
would form?
A.
Stratus clouds
B.
Cumulus clouds
C.
No clouds
D.
Cold clouds
In particular, cumulonimbus
clouds, which can cause
thunderstorms
Warm Front
 A warm front: the transition zone where a warm air mass is replacing a cold
air mass.
 Draw this:
1.
2.
3.
4.
a warm air mass (in yellow) meets a colder air
mass (in blue) ahead of it
The less dense warm moist air behind the
front is lifted upward and "overrides" the
colder air
As the air rises, it cools
widespread clouds (fog) and precipitation
develop until the front passes.
Warm Front
 As air moves horizontally at a warm front, what type of
clouds would form?
A. Stratus clouds
B. Cumulus clouds
C. No clouds
D. Warm clouds
Warm Front
 Which of these symbols represents a warm
front on a weather map?
A
B
C
Stationary Front
 When a warm or cold front
stops
moving, it becomes
a stationary front.
 Neither air mass is
strong enough to advance
 Can remain for several days
 Clouds and precipitation
 Once this boundary moves again, it once again becomes a
warm front or cold front.
Occluded Front
 when a cold front overtakes a warm front because it
moves faster
 Forms in areas of low pressure
 Usually brings even colder drier weather than before,
sometimes thunderstorms.
Temperature Inversions
 A reversal of the normal temperature profile in the lower
atmosphere
 Cooler air gets trapped underneath warmer air
 Can trap pollutants
 Often occurs in valleys