Download Atmospheric Circulation

Atmospheric Circulation
Wind
PAGE 122
Atmospheric Circulation AKA Wind!
• With all the talk about pollution, global warming
and climate change, why do we care? Let those
cities with the nasty air enjoy their nasty air by
themselves. . .
▫ This thinking leads into our next topic, does it
only affect the city that produces the pollution?
Unfortunately, no. Wind will carry that
pollution all over the globe making
this a global problem.
The driving force of wind:
Convection Currents
• Reminder
▫ Convection current: The
movement of matter due to
differences in density that
are caused by temperature
variations
• This unequal heating
transfers heat around the
world and causes
atmospheric circulation
Global Winds
• Earth has Three
convection cells in
each hemisphere that
transfer cold air from
the poles to the
equator and warm air
from the equator to the
poles
• These cells in turn
create the prevailing
winds, tornadoes,
hurricanes etc.
Atmospheric Convection Cells
• Polar Cell: air cools in the polar regions and flows
towards the equator (till about 60º latitude) where it
warms, rises, and returns to the poles
• Ferrel Cell: known as the “zone of mixing” because the
cold polar air from 60º latitude flows down and the
warm equatorial air from 30º latitude mix in this area
• Hadley Cell: warm air from the equator rises towards
30º latitude, cools and then flows back to the equator
What the cells do. . .
• All these cells “do” is transfer the heat
• This motion of air, in turn, causes the winds
• There are 3 major wind belts that generally blow
in the same direction all the time, these are
called the Global Wind Belts
Trade Winds
• Prevailing winds that blow from east to west
from 30º latitude to the equator in both
hemispheres
http://www.weatherwizkids.com/globalcirculation.gif
Westerlies
• Prevailing winds
that blow from
west to east
between 30º and
60º latitude in
both
hemispheres
Polar Easterlies
• Prevailing winds that blow from east
to west between 60º and 90º latitude
in both hemispheres
•
http://nsidc.org/arcticmet/images/factors/global_circulation.gif
Wind Patterns
• http://www.youtube.com/watch?v=IWjeHtdpFj
E
Coriolis Effect-Why the Winds
Curve!
• The apparent deflection
from a straight-line
path observed in wind
and ocean currents due
to Earth’s rotation.
• http://www.youtube.co
m/watch?v=rdGtcZSFR
Lk
The Doldrums and Horse Latitudes
• Surface winds that are weak and
variable that form where convection
cells meet
▫ Doldrums or Intertropical
Convergence Zone: forms at the
equator
▫ Horse Latitudes: forms at 30º latitude
Jet Streams
• A narrow band of strong winds that blow
in the upper troposphere (right before the
stratosphere)
• Big factor for determining weather
• In the upper parts of North America it
causes the Polar Vortex, it is actually
present year round in the North Pole, but
will migrate south
Local Winds
• Not part of the global wind belts, they
depend on local conditions
▫ Sea breeze – cool wind from water to
land
▫ Land breeze – cool wind from land to
water
▫ Mountain breeze – cool air descends
from mountain peaks
▫ Valley breeze – warm air from valleys
move upslope
Global Circulation
• http://www.youtube.com/watch?v=DHrapzHPC
SA
One More Random Note:
Temperature Inversions
• Normally, warm air
rises, cools and sinks
• Here in Utah the
topography of the area
traps cold air,
preventing circulation
▫ This, in turn, traps
pollutants also
Homework
• Complete the diagram provided by labeling the
following:
▫
▫
▫
▫
The 3 convection cells (6 total)
The 3 global wind belts (6 total)
The Horse Latitudes and Doldrums
Color the convection cells to show the hot air (red)
and cool air (blue)
• Answer questions 2-10 on page 125 of your
textbook (answer the questions on the back of
your diagram)