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Circulation in the atmosphere

Circulation in the Atmosphere. Circulation in the atmosphere. What drives the atmospheric circulation?. Two fundamental mechanisms Differential heating by the sun Rotation of the planet. Differential Solar Heating From Equator to Poles. Incoming solar radiation ~ 1370 W/m 2. X 23.

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Circulation in the atmosphere

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  1. Circulation in the Atmosphere Circulation in the atmosphere

  2. What drives the atmospheric circulation? • Two fundamental mechanisms • Differential heating by the sun • Rotation of the planet

  3. Differential Solar Heating From Equator to Poles Incoming solar radiation ~ 1370 W/m2 X 23

  4. Seasonal Heating

  5. Radiative Budget

  6. Radiative balance • Solar radiation is mostly in the visible band • Earth’s radiation is in infrared band

  7. Reflectivity and albedo • Albedo = fraction of energy reflected • Fully absorbing surface: a = 0 • Black surface ~ sea water • Fully reflecting surface: a = 1 • White surface ~ snow • At high latitudes • Cold ice/snow reflects solar radiation, making it even colder • Positive ice-albedo feedback

  8. Flow of energy in the atmosphere • Net heat gain in tropics • Net heat loss at high-latitudes • Atmospheric circulation is in part driven by the pole-equator differential heating • Atmospheric and oceanic circulations transport heat from low to high latitudes

  9. troposphere surface Higher Latitudes Equator/Tropics Vertical motions driven by heating / cooling Heating by the sun AIR PRESSURE

  10. Horizontal view of air pressure at the surface High Pressure + Higher Latitudes Surfaces of constant pressure y (latitude) x (longitude) _ Equator/Tropics Low Pressure

  11. Fluid accelerates towards low pressure regions

  12. Land-Sea Breeze

  13. Vertical view of air pressure (horizontal convection) High Pressure Low Pressure Low Pressure

  14. Non-rotating view of Atmospheric Circulation Hadley circulation: Tropics

  15. Rotation effect We are in the rotating frame of reference

  16. Tank demo Differentially heated annulus experiment Low lat. Low lat. “Pole”

  17. Differentially heated, rotating flow Baroclinic wave/vortices “Weather events” Look at the IR satellite images http://www.meteo.psu.edu/~gadomski/SAT_NHEM/atlanim16wv.html

  18. Differentially heated, rapidly rotating flow Wave/vortex motion naturally emerges:  Mid-latitude cyclones: weather events

  19. Ocean eddies Same mechanism: planetary rotation + temperature gradient

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