Transcript Air Masses and Fronts - Boone County Schools

Air Masses and Fronts
By: Lauren Malloy
T-5 Clancy’s
11-14-05
What are the four types of air masses?
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Maritime Tropical
Maritime Polar
Continental Tropical
Continental Polar
Maritime Tropical
• Warm humid air masses from
oceans near the tropics.
• They form over the Gulf of
Mexico and the Atlantic
Ocean.
• In the summer time maritime
tropical usually bring hot
humid weather.
• In winter, a humid air mass
can bring heavy rain or snow.
Maritime Polar
 Cool humid air masses form
over the icy cold North Pacific
and North Atlantic oceans.
 The air masses affect the west
coast more than the east coast.
 In the summer they often
bring rain, fog, and cool
temperatures to the west coast.
Continental Tropical
 Hot dry air masses form only
in the summer over dry areas
of southwestern and
northern Mexico.
 Cover a smaller area than
other air masses.
 Bring hot, dry weather to the
south.
Continental Polar
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Form over central and
northern Canada and
Alaska.
Bring cool and cold air.
In winter they bring clear,
cool, and dry air to most
of northern America.
In the summer, storms may
occur when continental air
masses move south and
meet maritime tropical that
move north.
How do air masses move?
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The prevailing westerlies are
the major wind belts in the
United States.
Prevailing westerlies push air
masses from west to east.
Fronts
 When air masses meet is a
front, the collision often
causes storms and weather
changes.
 A front may be 15 to 200
kilometers wide and extend
as much as 10 kilometers up
to the troposphere.
 The kind of front that
develops depends on the
characteristics of the air
masses and how they move.
There are four types of fronts.
 Cold Fronts.
 Warm Fronts.
 Stationary Fronts.
 Occluded Fronts.
Cold Fronts
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Cold air is dense and tends to sink.
Warm air is less dense and tends to
rise.
When a moving cold air mass runs
into a slowly moving warm air
mass, the denser cold air slides
under the warmer air.
Warm air can hold more water
vapor than cool air.
If there is a lot of water vapor in
the warm air heavy rain or snow
may fall.
Cold fronts move quickly so they
can cause weather changes.
After a cold front passes, cool, dry
air moves in.
Warm Fronts
 A moving warm air mass
collides with a slowly moving
cold air mass.
 If the warm air is humid
showers and light rain might.
fall along the front where the
warm and cold air meet.
 If the warm air is dry scattered
clouds may form.
 After a warm front passes
through an area the weather is
likely to be warm and humid.
 Winter warm fronts bring
snow.
Stationary Fronts
 Sometimes cold and warm air
masses meet but neither one
has enough force to move.
 Where the warm and cold air
meet, water vapor in the
warm air turns into rain,
snow, fog, or clouds.
Occluded Fronts
 A warm air mass is caught
between two cooler air
masses.
 As warm air cools and its
water vapor condenses, the
weather may turn cloudy,
rainy, or snowy.
Cyclones and Anticyclones
 As warm air at the center of a cyclone rises , the air
pressure decreases.
 Winds in s cyclone spin counterclockwise in the
Northern Hemisphere.
 As air rises in a cyclone the air cools forming clouds
and precipitation.
 Winds spiral outward from the center of an
anticyclone, moving towards areas of low pressure.
 Winds in an anticyclone spin clockwise in the
Northern Hemisphere.
Cyclones
 Hurricanes are very
large cyclones that
can cause
widespread damage.
Anticyclones
 Air flows clockwise
around a highpressure system in
the northern
hemisphere.
 Air tends to sink near
high-pressure
centers, which
inhibits precipitation
and cloud formation.
Vocabulary
 Air mass- a huge body of air that has similar temperature,
humidity, and pressure.
 Tropical- or warm air masses form in the tropics and have low
air pressure
 Polar- or cold air masses from North of 50o N latitude and
South of 50o S latitude.
 Maritime- air masses that form over oceans
 Continental- air masses form over land in the middle of
continents and are dry.
 Front- the area where the masses meet and do not mix.
 Occluded- the warm air masses is cut off.
 Cyclone- a swirling center of low air pressure.
 Anticyclone- area of high pressure centers of dry air.
Section 1 Review
1.) What two main characteristics are used to classify air
masses?
 Temperature
 Humidity
Section 1 Review
2.) What's a front? Name and describe the four fronts.
 Front- the area where the masses meet but do not mix.
 Cold Fronts- when a rapidly moving cold air mass runs into a
slowly moving air mass, the denser cold air slides under the
lighter warm air.
 Warm Fronts- a moving warm air mass collides with a slowly
moving cold air mass.
 Stationary Fronts- sometimes cold and warm air masses meet
but neither one has enough force to move.
 Occluded Fronts- a warm air mass is caught between two
cooler air masses.
Section 1 Review
3.) What is a cyclone? What kind of weather does it
bring?
 Cyclone- a swirling center of low air pressure.
 A cyclone usually brings precipitation and usually forms
clouds.
Section 1 Review
4.) Why do maritime polar air masses have more
affect on the west coast than the east coast?
 Maritime polar air masses has more affect on the
west coast than the east coast because,
of the cool humid air.