Atmospheric and Oceanic Circulation

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Atmospheric and Oceanic Circulation

• September 18, 2007

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Coriolis

• Deflects motion to the right in the Northern
  Hemisphere, and to the left in the Southern
  Hemisphere
• What is the rotational velocity at different
  latitudes?

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Atmospheric Circulation
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Atmospheric Circulation

• What drives atmospheric circulation?
• Heating
• Coriolis
• What does atmospheric circulation affect?

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Effects on Temperature
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Effects on Salinity
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Ocean Currents

• What drives ocean surface currents?

http//www.onr.navy.mil/focus/ocean/motion/current
s1.htm
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Ocean Currents
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Subtropical Gyres

• Strong,Warm Western Boundary Current
• Weak, Cold Eastern Boundary Current
• Equatorial Current

http//earth.usc.edu/stott/Catalina/images/Oceano
graphy/9-3.jpg
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Ekman Spiral

• What causes the Ekman spiral?
• How deep does the Ekman spiral have an effect?

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Upwelling
West Coast of South Africa
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Thermohaline Circulation

• Deep currents
• Driven by changes in density
• Downwelling - formation of deep water
• Upwelling - surfacing of deep water
• Where is deep water formed?

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http//meteo.lcd.lu/papers/Conference_ICN/ocean_co
nveyor_belt.gif
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Waves

• A wave is energy transmitted through some medium
  (which can be solid, liquid, or gas)

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Wave Terminology

• Wave Period The time it takes for one full
  wavelength to pass
• Wave Speed Wavelength/Wave Period

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Types of Surface Waves
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Internal Waves

• Waves can also existalong density
  discontinuities beneath the ocean surface
  these are called internal waves
• Can travel in 3 dimensions (instead of just 2),
  and generally have longer wavelengths and have
  slower speeds than surface waves

http//www-ccs.ucsd.edu/iwaves/
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Tides

• Centrifugal Force pulls an orbiting body
  towards the center of its orbit
• Gravitational Force between two objects
  proportional to the product of their masses and
  inversely proportional to the square root of the
  distance between them

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Earth-Moon System
Semidiurnal Tides
http//www.lhup.edu/dsimanek/scenario/img008.gif
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The Effect of the Sun
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Declination of the Moon

• The moon can sit right at the equator of the
  earth, or be at an angle of up to 28.5? depending
  on where it is in its orbit
• Daily inequality in the semidiurnal tides

http//www.fhwa.dot.gov/engineering/hydraulics/ima
ges/h25_b6.jpg
http//www.oceanservice.noaa.gov/education/kits/ti
des/media/tide04_240.gif
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Mixing in the Surface Ocean

• Mixed Layer
• Thermocline
• Where would we expect to see the least and most
  surface mixing?

http//www.ccfhr.noaa.gov/images/events/mixing
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Mixing Beneath the Surface

• Shear vertical gradients in horizontal
  velocities
• Turbulence small-scale mixing
• How long does it take the entire ocean to mix?

http//www.physics.mun.ca/danielb/research/aestus
/MI_web.jpg
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• Slow and small-scale mixing
• Mixing and diffusion combined?