Transcript The Atmosphere

Why is the equator
warmer than the poles?
The rays of the
sun strike the
Earth directly at
the equator. At
the poles the
curvature of the
Earth spreads the
rays out.
The solar radiation heats
the surface of the earth.
Heat is transferred to air molecules
that come in contact with the ground.
If all the air is rising,
Why doesn’t this
person suffocate?
The solar
radiation
heats the
surface of
the earth.
Heat is transferred to air molecules
that come in contact with the ground.
As the
Warmer Air
Rises…
Cooler air is pulled
in from other places
What is this called?
Convection current –
the transfer of heat
through movement in
the atmosphere.
The Wind
 Winds are the result of uneven
heating of the Earth’s surface
– This uneven heating
causes differences
in air pressure
to develop
– Molecules always
move from areas of
high pressure to
areas of low
pressure
GLOBAL PRESSURE & WIND
North Pole 90°N
Arctic circle 66.5°N
HIGH
HIGH PRESSURE
LOW
ZONE of greatest
heating produces
LOW PRESSURE
Tropic of Cancer
23.5°N
Equator 0°
Tropic of Capricorn
23.5°N
Antarctic circle 66.5°S
ZONE of least heating produces
HIGH
ZONE of least heating produces
HIGH PRESSURE
North Pole 90°N
How would you expect air to move across the planet?
GLOBAL PRESSURE & WIND
Global circulation depends on differential heating over
the globe.
The system is driven by strong equatorial heating,
causing LOW PRESSURE.
POLAR HIGH
EQUATORIAL LOW
GLOBAL PRESSURE & WIND
Equatorial air descends over the tropics, where HIGH
PRESSURE dominates; where it diverges at ground
level. This tropical air blows towards the equator,
completing the equatorial cell.
POLAR HIGH
TROPICAL HIGH
EQUATORIAL LOW
GLOBAL PRESSURE & WIND
Some of the sinking air at the Tropical High moves
towards the mid-latitides where it meets cold, dense polar
air blown out from the polar HIGH PRESSURE.
POLAR HIGH
TROPICAL HIGH
EQUATORIAL LOW
GLOBAL PRESSURE & WIND
These contrasting tropical and polar air masses meet at the
POLAR FRONT LOW PRESSURE BELT, where the
warmer air is forced upwards by the polar air.
POLAR HIGH
POLAR FRONT (LOW PRESSURE)
TROPICAL HIGH
EQUATORIAL LOW
High
CORIOLIS FORCE
Theoretical wind
which would result
solely from pressure
gradient
Actual wind
which blows, as
diverted by
Coriolis Force
Low
Merry Go Round Demonstration
Coriolis Explained
Pressure gradient wind
blows from high pressure
towards low pressure.
� The earth’s rotation diverts
this wind direction sideways.
This force is called the
CORIOLIS FORCE.
� The Coriolis force diverts
wind the the right in the
northern hemisphere; to the
left in the south.
�
Trade
Easterlies –
Winds
pattern–of
Westerlies
pattern
air
of
– pattern
air
movement
of air
movement
at
the
movement
in
poles
in the
the midtropics
latitudes
Goes to
Goes
the midto
the
latitudes
equator
the
poles
Why do the gas giants appear to
have a striped surface?
Jet Stream – is a band
of fast moving air in
the stratosphere.
Formed where
Westerly winds meet
the Easterly winds
Jet Stream Video
Summarizing Convection
 What is convection?
 Where does convection occur?
 In what states of matter does
convection occur?
 What other liquid could convection
occur in on Earth?
Ocean Currents
 Atmospheric
Currents
– Depend on
temperature
 Ocean Surface
Currents
– Depend on wind
Ocean Currents
Ocean Currents
Ocean Currents
Wind driven
currents
Wind-drive
oceansurface
surface currents
• How fast? A few miles/hr (Gulf Stream off of Miami = 4.5 mph)
• How much? Total water in ocean surface circulation = about 100
Amazon Rivers (20 million m3/s).
Ocean Currents Illustrated
 Green Peace
 Today Show Investigates