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Weather
Atmospheric Movement
 Global air
circulation
patterns within
the atmosphere
held to Earth by
gravity and
warmed as heat
radiates from
Earth
Coriolis Effect
 The apparent
defection of
moving air, as
seen by an
observer on
Earth; apparent
defection is a
result of Earth's
rotation
Air Pressure
The force exerted on
Earth’s surface by the
weight of the air above the
surface
Air pressure is greatest at sea
level and lessens with increased
distance from Earth’s surface.
Wind
 A natural movement of air
sometimes with considerable
force from an area of high density
and pressure to an area of low
density and pressure
Air Masses
An air mass is a body of air
extending over a large area
(1,000 miles or more) that
develops and retains
specific characteristics of
pressure, temperature and
humidity
 An air mass forming over a hot
desert would be dry and hot.
 One forming over a cold marine
surface would be cold and humid.
High-Pressure Air Mass
 An air mass with
greater
atmospheric
pressure than the
surrounding air
masses; air moves
away from the high
pressure, traveling in
a clockwise
direction
High-Pressure Air Mass
 HIGHS are denser, cooler and dryer
than the adjacent air. The air is descending
toward Earth’s surface.
 HIGHS bring pleasant weather
conditions in the summer and very
cold clear weather in the winter.
Low-Pressure Air Masses
 An air mass with
less atmospheric
pressure than the
surrounding air
masses; air moves
towards the low
pressure, traveling
in a
counterclockwise
direction
 Lows bring stormy
weather.
Warm Front
 Forms at the surface of Earth when
a warm, moist air mass
overtakes a cool, dense and
dryer air mass
 Slow moving and are
characterized by a series of clouds
getting lower and thicker as the
front approaches.
Warm Front
Cold Front
 Forms at the surface of Earth when
a cold, dry air mass overtakes
a warmer, humid air mass
 Cold fronts are characterized by
dramatic storms, thunder,
lightning and sometimes
tornadoes.
Cold Front
Hurricane
 A large, tropical
weather system
consisting of an
extreme low
pressure air mass
with heavy rains
and wind speeds of
at least 119km/h
 Needs warm water
to develop and stay
strong