Transcript Air Pressure and Wind

22.3
Atmospheric Circulation
It all starts with unequal heating of Earth that cause
differences in pressure – resulting in air movement
• Warm air is less dense, rises
and creates LOW pressure
• Cold air is more dense, sinks
towards Earth’s surface and
creates HIGH pressure.
• Air flows from poles (H) to
equator (L)
• Air near Earth’s surface flows from the poles
to the equator because of the spin of the
Earth.
• Earth’s diameter is greatest at the equator and
smaller at the poles.
• The equator must travel faster to complete
one rotation than the poles.
• The air moves more slowly than the ground
beneath it does.
• This causes the air to flow from the poles
toward the equator.
• High pressure regions form where cold air
sinks towards Earth’s surface.
• Low pressure regions form where warm air
rises away from Earth’s surface.
• Circulation of the atmosphere and of the
oceans is affected by the rotation of Earth on
its axis.
• Earth’s rotation causes its diameter to be
greatest through the equator and smallest
through the poles.
• Points bear the equator travel further in a day.
Coriolis Effect
• Moving objects follow a
curved path due to Earth’s
rotation.
• Deflected right in northern
hemisphere (Clockwise)
• Deflected left in southern
hemishphere
(Counterclockwise)
• Detectable only on objects
that move very fast or over
long distances.
Global Winds – 3 looping patterns
called wind belts
• Wind flows from
poles to equator in
convective cells.
• Each cell correlates
to a wind belt that
forms wind that
flows one way.
(prevailing wind)
• Wind is named for
the direction it
come from.
• Winds that blow from E to W from 30*
latitude to the equator are the trade winds.
• In the N Hemisphere, trade winds flow from
the northeast.
• Prevailing winds that blow W to E are the
westerlies.
• Winds from 60-90* E-W are the easterlies.
• Stormy regions where easterlies meet
westerlies are fronts.
• Doldrums – form at
equator where the
warm air moves upward
and there is little wind.
• Horse Latitudes –form
at 30 degrees N and S
where the air decends
and there is little wind
Jet Stream
Narrow band of strong wind
that blows in the upper
troposphere
• Air movement caused by local conditions &
temperature are local winds.
• Breeze – gentle winds that extend over
distances of less than 100km
Local Wind – not part of global
wind
belts
Sea Breeze – cool
wind moving
from water to
land in afternoon
L
H
Warm Land
Cool Water
Land Breeze – cool
wind moving from
land to water at
night
H
Cool Land
L
Warm Water
Valley Breeze – warm
air from the valley
moves upslope during
day
Mountain Breeze –
cool air descends
from mountain peak
at night
• Mountain Breeze