Ocean and Atmospheric Circulation
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Transcript of Ocean and Atmospheric Circulation
Ocean and Atmospheric Circulation
Susan Howard Earth & Space Research
Basically – why and how the ocean and atmosphere MOVE!
www.ametsoc.org
There are many scales of motion: From BIG to very small
Today – I will just cover the basic large scale, GLOBAL circulation.
The Ocean and Atmosphere are in CONSTANT motion
NASA/Goddard Space Flight Center Scientific Visualization Studio
NASA Movie: Perpetual Ocean
Model of ocean currents based on data from satellites and other measurements.
There are 2 main things that form the Global Ocean and Atmospheric circulation patterns
set up the climate system we know it.
• Energy from the Sun
• Rotation of the earthWarming from the sun Sets it in Motion
The rotation directs the motion
Energy and the Sun
The Sun is constantly emitting energy, in the form of “electrogmagnetic radiation”.
What is ELECTROMAGNETIC RADIATION?
• Light• Infrared (Heat)• Xrays• Microwaves• Ultraviolet radiation (sunburns!)
Solar radiation travels through space and hits the earth and warms it.
The Heating of the Earth is Not Even!
Short length of day
Small angle of incidence/ low intensity Large amounts of Ice cover
Noon in Antarctica May
23rd, 2001
UNEVEN HEATING: The daily amount of warming at a point on the Earth depends on 3 things
The Heating of the Earth is Not Even!
• Length of Day - How much sunlight a point receives in a day
• Angle of Incidence (Intensity) – the angle of the sunlight that reaches the earth
• Albedo – how much of this light is reflected.
Length of Day
• Earth is tilted with respect to Sun• Length of day changes throughout the year
Source: Wikipedia
NH Summer
NH Winter
Length of Day
Source: Wikipedia
Equinox
Solstice
Angle of Incidence
A beam of light shining straight down is more intense that a beam of light shining at an angle
The angle the incoming light makes with respect to the Earth
Angle of incidence
Wikipedia
Intensity of Radiation Varies with Latitude
The further you get from equator, the less radiation reaches the earth per area
Source: http://atschool.eduweb.co.uk/kingworc/departments/geography/nottingham/atmosphere/pages/solarradiationalevel.html
Because the Polar regions receive less radiation, they are cooler.Because they are cooler – ice forms.
It reflects the solar radiation
What does Sea Ice do?
High albedo – high reflectionLow albedo – high absorption
Ice cover – reflects radiation
Radiation reflected
Radiation absorbed
Warms water
So Ice makes the polar regions even cooler!
So, because of angle of incidence, length of day, & ice:
Equator
Pole
The Equator gets more heat than the Poles ...
a lot more!
Warmer Cooler
Average Annual Heating by Sun
Source: Wikipedia
Ocean temperature movieFrom NOAA, Based on satellite measurements
What does this Uneven Heating do?
• Hot air and cold air behave differently
Hot air risesCold air will sink.
• And this causes MOTION
Warm air rises
Cold air sinks
How Wind Forms
Low Pressure
HighPressure
Wind
Wind
Convection Cell
****Air likes to go from areas of High pressure to Low pressure
The GLOBAL Air Circulation is controlled by these convection cells
Figure 7.5 in The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001.
So, we know:
1)The SUN heats the earth UNEVENLY – And this is going to cause motion.a. The uneven heating causes the rising and sinking
of airb. And this rising and sinking causes WIND.c. The sun has set the atmosphere in motion
2) What going to now DIRECT this motion ?
ROTATION of the Earth
2) Rotation of the Earth it helps DIRECT the circulation.
It works at right angles to motion and makes the motion curve
Coriolis Force
Equator
Right in Northern Hemisphere
Left in Southern Hemisphere
Coriolis Force
Global Wind Patterns
No Rotation
With Rotation
http://www.srh.noaa.gov/jetstream/global/circ.htm
Global wind patterns based on Solar heating and Rotation
Early Explorers relied on the global wind patterns to sail around the world
Summary Movie – Air circulation
Movie : Global Atmospheric Circulation By Keith Meldahl, YouTube video
Sun’s Heating and Earth’s rotation create wind circulation patterns
creates Global Surface Currents in Ocean
Wind motion creates Surface Currents in Ocean
Map of basic surface currents
http://oceanmotion.org/html/background/wind-driven-surface.htm
Wind AND ocean currents
http://staff.orecity.k12.or.us/steve.tebor/atm%20currents/current/images/world_circulation.jpg
Because of uneven heating, just like the Atmosphere, the ocean also has Convection Cells which drives DEEP circulation
The Wind drives large scale surface currents but that isn’t all.
Basic facts
Warm WATER rises Cold WATER sinks
Warm air rises Cold air sinks
Ocean Conveyer Belt
Ocean circulation – major currents
Movie : GFDL Ocean current move
Questions?