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Ocean and Atmospheric Circulation

Susan Howard Earth & Space Research. Ocean and Atmospheric Circulation. Basically – why and how the ocean and atmosphere MOVE!. There are many scales of motion: From BIG to very small. Today – I will just cover the basic large scale, GLOBAL circulation. www.ametsoc.org .

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Ocean and Atmospheric Circulation

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  1. Susan Howard Earth & Space Research Ocean and Atmospheric Circulation Basically – why and how the ocean and atmosphere MOVE! There are many scales of motion: From BIGto very small Today – I will just cover the basic large scale, GLOBAL circulation. www.ametsoc.org 

  2. The Ocean and Atmosphere are in CONSTANT motion NASA Movie: Perpetual Ocean Model of ocean currents based on data from satellites and other measurements. NASA/Goddard Space Flight Center Scientific Visualization Studio

  3. set up the climate system we know it. There are 2 main things that form the Global Ocean and Atmospheric circulation patterns • Energy from the Sun • Rotation of the earth Warming from the sun Sets it in Motion The rotation directs the motion

  4. 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!)

  5. Solar radiation travels through space and hits the earth and warms it. The Heating of the Earth is Not Even!

  6. UNEVEN HEATING: The daily amount of warming at a point on the Earth depends on 3 things Short length of day Small angle of incidence/ low intensity Large amounts of Ice cover Noon in Antarctica May 23rd, 2001

  7. 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.

  8. Length of Day NH Summer NH Winter Source: Wikipedia • Earth is tilted with respect to Sun • Length of day changes throughout the year

  9. Length of Day Equinox Solstice Source: Wikipedia

  10. Angle of Incidence The angle the incoming light makes with respect to the Earth A beam of light shining straight down is more intense that a beam of light shining at an angle

  11. Angle of incidence Wikipedia

  12. 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

  13. Because the Polar regions receive less radiation, they are cooler. Because they are cooler – ice forms. What does Sea Ice do? It reflects the solar radiation High albedo – high reflection Low albedo – high absorption

  14. Ice cover – reflects radiation Radiation reflected Radiation absorbed Warms water So Ice makes the polar regions even cooler!

  15. So, because of angle of incidence, length of day, & ice: The Equator gets more heat than the Poles ... a lot more! Equator Pole Warmer Cooler

  16. Average Annual Heating by Sun Source: Wikipedia

  17. Ocean temperature movie From NOAA, Based on satellite measurements

  18. What does this Uneven Heating do? • Hot air and cold air behave differently Hot air rises Cold air will sink. • And this causes MOTION

  19. How Wind Forms Wind Warm air rises Cold air sinks Convection Cell Wind Low Pressure High Pressure ****Air likes to go from areas of High pressure to Low pressure

  20. The GLOBAL Air Circulation is controlled by these convection cells Figure 7.5 in The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001.

  21. So, we know: • The SUN heats the earth UNEVENLY – And this is going to cause motion. • The uneven heating causes the rising and sinking of air • And this rising and sinking causes WIND. • The sun has set the atmosphere in motion 2) What going to now DIRECT this motion ? ROTATION of the Earth

  22. 2) Rotation of the Earth it helps DIRECT the circulation. Coriolis Force It works at right angles to motion and makes the motion curve

  23. Coriolis Force Right in Northern Hemisphere Equator Left in Southern Hemisphere

  24. Global Wind Patterns With Rotation No Rotation http://www.srh.noaa.gov/jetstream/global/circ.htm

  25. Global wind patterns based on Solar heating and Rotation Early Explorers relied on the global wind patterns to sail around the world

  26. Summary Movie – Air circulation Movie : Global Atmospheric Circulation By Keith Meldahl, YouTube video

  27. Sun’s Heating and Earth’s rotation create wind circulation patternscreates Global Surface Currents in Ocean

  28. Wind motion creates Surface Currentsin Ocean

  29. Map of basic surface currents http://oceanmotion.org/html/background/wind-driven-surface.htm

  30. Wind AND ocean currents http://staff.orecity.k12.or.us/steve.tebor/atm%20currents/current/images/world_circulation.jpg

  31. Because of uneven heating, just like the Atmosphere, the ocean also has Convection Cellswhich drives DEEP circulation The Wind drives large scale surface currents but that isn’t all.

  32. Basic facts Warm air rises Cold air sinks Warm WATER rises Cold WATER sinks

  33. Ocean Conveyer Belt

  34. Ocean circulation – major currents Movie : GFDL Ocean current move

  35. Questions?

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