Transcript 3.1 Weather changes as air masses move

Weather Systems
Air mass
 Definition-
large body of air that
sits over land/water for many
days.
 The air takes on the
characteristics of the land or
water below it.
Characteristics of an Air Mass
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Air masses are classified by a combination of
two words: the first word represents where the
air mass forms, and the second represents
temperature.
– Continental: forms over land, air becomes dry
– Maritime: forms over water, air becomes
moist
– Tropical: forms near equator, air becomes
warm
– Polar: form far from equator, air becomes cool
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This type of air mass forms over land and
near the equator.
This type of air mass forms over water and
far away from the equator.
This type of air mass forms over land and far
from the equator.
This type of air mass forms over water and
near the equator.
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FRONTS
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Definition- A front is the boundary (space) in
between two air masses
When two air masses meet, weather is
created and will change!
Some of those changes include: cloud
formation, stormy weather, precipitation
After the air mass moves in, you experience
the temperature and humidity of that air
mass.
Types of fronts
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Cold Front: cold air mass pushes a warm air
mass causing the warm air to rise.
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As warm air rises it condenses forming tall clouds!
Can bring heavy rain and stormy weather
Types of fronts cont…
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Warm front: Forms when a warm air mass
pushes a cold air mass. Warm air slowly
rises over the cold air and the moisture from
the warm air condenses into flat clouds.
Brings many hours of light rain or snow.
http://www.mesoscale.iastate.edu/agron206/animations/05_cnWfronts.html
Types of fronts cont…
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Stationary front: occurs when two air masses
push against each other without moving. Can
become either a warm or cold front
depending on which air mass moves first.
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Pressure systems
Definition- an area where there is either very
high pressure or very low pressure in that
region.
 Symbolized
with a H or an L
on a weather
map
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HIGH PRESSURE SYSTEM
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At a high pressure center, air sinks down
slowly.
Air spreads out to areas of low pressure.
High pressure system is formed when air
moves all the way around a high pressure
center. Usually very large and change slowly.
Generally brings clear skies, calm air, and
gentle breezes because as air sinks it warms
causing water droplets to evaporate so
clouds disappear.
LOW PRESSURE SYSTEM
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Large weather system that surrounds a
center of low pressure. Air moves inward and
upwards to higher altitudes. The faster the
movement, the stronger the system.
Rising air produces stormy weather and can
form when two air masses meet.
Tropical storms, hurricanes, storm surges,
blizzards, snowstorms, and ice storms are all
created from low pressure systems.
Pressure system cont..
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Barometer
measures air
pressure
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