Types of Air Masses
What is an Air Mass?
A body of air that has same
temperature, humidity, and air pressure.
Usually cover thousands of square
kilometers
They are classified by where they form
Types of Air Masses
There are four main types of air
masses.
1. Tropical - warm, air masses with a low
pressure.
2. Polar - cold air masses with high
pressure.
3. Maritime - form over the ocean and are
very humid (wet).
4. Continental - form over land and are dry.
Air Masses
Four major types of air masses
influence the weather in North America:
1. Maritime Tropical
2. Continental Tropical
3. Maritime Polar
4. Continental Polar
Types of Air Masses
Maritime Tropical
Warm, humid air mass that form over oceans.
If they form over the Gulf of Mexico, they
influence weather in the southern, central and
eastern US.
If they form over the Pacific Ocean, they
effect the weather on the West coast.
In summer they bring hot, humid weather
causing showers and thunderstorms.
In winter they can bring heavy rain or snow.
Maritime Tropical
Maritime Polar
Cold, humid air masses that form over
the icy cold North Pacific and North
Atlantic Oceans.
They mostly effect the West coast
bringing fog, rain and cool
temperatures.
In the winter, they bring heavy snow and
cold temperatures.
Maritime Polar
Continental Tropical
Hot, dry air masses that form only in
summer over dry areas in the
Southwest and northern Mexico.
Continental Tropical
Continental Polar
Large air masses that form over
Canada and Alaska.
They bring cold dry air.
Continental Polar
North American Air Masses
Fronts
When two air masses that do NOT have
the same properties meet, they do not
mix. Instead, a boundary forms that is
called a front.
The weather at a front is usually stormy
and unsettled
Named after whichever air mass is the
“attacker”.
Cold Front
Forms when a cold air mass meets and
pushes under a warm air mass.
The cold air mass forces its way underneath
the warm air mass and pushes it upward.
Violent weather is associated with a cold front
and then fair, cool weather follows.
Travels faster than warm fronts.
Cold Front
Weather Map - Cold
Warm Front
Forms when a mass of warm air
overtakes a cold air mass and moves
over it.
Light rain and showers usually
accompany it and then hot, humid
weather follows.
Warm Front
Weather Map - Warm
Stationary Front
Formed when a warm air mass meets a
cold air mass and NO MOVEMENT
OCCURS.
Rain may fall in an area for many days.
Weather produced is similar to a warm
front.
Stationary Front
Weather Map - Stationary
Occluded Front
Forms when a cold front overtakes a warm
front. As the warm air is pushed upward, the
cold air meets cool air.
It may also form when cool air overtakes a
cold front and warm air is pushed upward.
Produces less extreme weather than a cold
front or a warm front.
Usually cool temperatures and large amounts
of precipitation.
Occluded Front
Weather Map – Occluded