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.