Transcript Weather Systems

Weather Systems
SWBAT describe how the rotation of
Earth affects the movement of air;
compare and contrast wind systems;
identify the various types of fronts.
Global Wind Systems
 Coriolis effect
– The rotation of earth causes particles such as
air to be deflected to the right in the northern
hemisphere and to the left in the southern
hemisphere
With a partner
 In your own words describe how the rotation
of Earth affects air movement.
– The Coriolis effect causes air molecules to be
deflected to the right in the northern hemisphere
and the left in the southern hemisphere. This,
along with the imbalance of heating due to the
angle sunlight strikes the earth, creates distinct
global wind systems that transport warmer air to
colder areas and vice versa. The result is a
balancing of heat energy on Earth.
Global Wind Systems
 Trade winds
– Occur at 30° north and south latitude.
– Air sinks, warms and moves toward the equator in a
westerly direction.
– When the air reaches the equator it rises again and
moves back toward 30° latitude, where the process
starts again.
– At 30° latitude there is a high pressure belt that causes
weak face winds.
– At the equator there is a low pressure zone called the
intertropical convergence zone
Global Wind Systems
 Prevailing Westerlies
– These winds flow between 30°N and 60°N as
well as 30°S and 60°S.
– They flow in a pattern opposite to the trade
winds, with surface winds blowing toward the
poles in a generally easterly direction.
– These are responsible for the weather in the
US.
Global Wind Patterns
 Polar Easterlies
– These winds lie between 60°N and S and the
respective poles.
– They are similar to the trade winds, flowing from
northeast to southwest in the northern
hemisphere, and southeast to northwest in the
southern hemisphere.
– They are characterized by their cold air.
Global Wind Patterns
 Jet streams
– Narrow bands of fast, high altitude, westerly
winds. They can flow up to 185 km/h.
 How does the jet stream affect weather?
– Jet streams cause disturbances, creating large
scale weather systems. It affects the intensity
of weather by moving air of different
temperatures from one region to another.
In groups of 2-3
 You will create a model of a globe that illustrates the global
wind patterns we have studied .
 You must mark the following latitudes on your globe:
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Equator = 0°
Horse latitudes = 30°N and 30°S
60°N and 60°S
Poles = 90°N and 90°S
 Also label the northern and southern hemispheres
 You must include:
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Trade winds pattern
Prevailing westerlies pattern
Polar easterlies pattern
Coriolis effect
Intertropical Convergence Zone
Polar jet stream
Subtropical jet stream
Fronts
 Front
– The narrow region separating two air masses of
different densities (caused by differences in
temperature, pressure, and humidity)
Front Types
 Cold front
– Cold dense air displaces warm air and forces it
upward in a steep front.
– Clouds, showers, and thunderstorms are
associated with cold fronts.
– It’s represented on a weather map by a solid
blue line with blue triangles
pointing in the direction of
the front.
Front Types
 Warm Front
– Advancing warm air displaces cold air. Due to
the slow movement of the cold air it develops a
gradual slope.
– It’s characterized by extensive cloudiness and
precipitation.
– It’s represented on a weather chart by a solid
red line with semicircles facing in the
direction of the front’s movement.
Front Types
 Stationary Front
– When 2 air masses meet and neither advances
into the other’s territory the boundary stalls.
– They seldom have clouds or precipitation, but
can be similar to the weather of a warm front.
– It’s represented on a weather chart by a
combination of warm and
cold fronts symbols.
Front Types
 Occluded Front
– Occurs when a cold air mass moves rapidly and
overtakes a warm front. The cold air wedges
itself under the warm air, forcing it upward.
When it forces the warm out of the way it
collides with another cold front.
– Precipitation is common on both sides of an
occluded front.
– It’s represented on a weather
map with an alternating line of
purple triangles and semicircles
Pressure Systems
 Describe and illustrate air movement in a
high pressure system.
– Air sinks and then spreads away from the
center. It moves in a clockwise direction in the
northern hemisphere and counterclockwise in
the southern, due to the Coriolis effect.
– Associated with fair weather.
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Pressure Systems
 Describe and illustrate air movement in a
low pressure system.
– Air rises from the surface and is replaced by air
from outside the system pulling it toward the
center. It moves in a counterclockwise direction
in the northern hemisphere and a clockwise
direction in the southern
hemisphere.
– Associated with clouds
and precipitation.
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With a partner
 Answer questions 1-6, on page 311.
 Be sure to answer in complete sentences.
 If you don’t finish in class you must
complete this for homework.