Air Masses
and how they control our weather
Air Mass
 An air mass is a body of air with similar
properties throughout.




Similar temperature.
Similar moisture content.
Can be thousands of km across.
Categorized by where they form.
Types of Air Masses
 Basic categories of air masses.
P = Polar air mass
T = Tropical air mass
A = Arctic air mass
 Two designations of surface where formed.
m = maritime (formed over ocean)
c = continental (formed over land)
Different types of Air Masses
 continental Arctic (cA)
 Dry, very cold
 continental Polar (cP)
 Dry, cold
 continental Tropical (cT)
 Dry, warm
 maritime Polar (mP)
 Moist, cool
 maritime Tropical (mT)
 Moist, warm
Air Masses Worldwide
Air Masses Affecting N. America
Air Masses Affecting N. America
North American Air Masses - Polar
 continental Polar (cP) and continental Arctic (cA)


Form over Northern Canada and Northern Alaska
Cold and dry air masses.


In summer bring cool dry weather
In winter bring very cold weather to northern states.
 maritime Polar (mP)



Mainly form over northern Pacific and S.W. Alaska
Pacific Northwest is mostly affected by them.
Cool and humid air.




In winter, bring rain and snow to Pacific Coast.
In summer, bring cool, foggy weather.
Lose much moisture as they travel over the Sierra Nevada and Rocky
mountains, so they bring dryer air to the mid U.S.
Occasionally form over Northern Atlantic and swing eastward.

Brings heavy snow to N.E. Atlantic states.
North American Air Masses - Tropical
 maritime Tropical (mT)
 Originate from the Gulf of Mexico, Caribbean Sea, or
Western Atlantic
 In summer, bring hot and humid weather to the
Eastern U.S. and Central U.S.
 In winter, bring much of the precipitation over the
Eastern and Central U.S. when the air mass is forced
up over the colder polar air masses.
 continental Tropical (cT)
 Do not have a big influence over weather in the U.S.
 North America is so narrow in the south that there’s
not much room for them to form.
 Can bring very hot and dry air.
Air masses and Alaska
 continental Arctic (cA) and continental Polar (cP)
 Cause the bone-chilling cold and dry air that much of
interior Alaska experiences in the winter.
 Can bring very cold temperatures to the Anchorage
bowl.
 maritime Polar (mP)
 This air mass has a huge affect on Anchorage’s
weather
 Causes our mild and wet summers.
 Causes our cool and snowy winters.