Heat and Atmospheric Circulation
Solar Energy
Sun is a star of average size, temp. & colorSun captured 99.9% of nebula’s matter.1% formed planets, moons, comets, asteroids & debrisSun is only object able to sustain fusion
Solar Energy Transmission
Energy intercepted @ top of atmosphereEarth’s distance from Sun results absorption of only 1/2 billionth of total energyEarth’s curved surface presents continually varying angle to parallel solar radiation
Uneven Solar Heating
Equator receives 90° angleOther radiation arrives at more oblique angle2.5 times more energy @ equator than poles in 1 year
Earth’s Heat Budget
51% on incoming solar energy is absorbed by Earth’s land and water surfaceLight striking land and sea are converted to heatThen, heat is transferred into atmosphereThe atmosphere eventually radiates this heat into space
Earth’s Heat Budget
Total incoming heat (plus heat released from Earth’s interior) equals the total heat radiated into space - Heat Budget
Earth is in thermal equilibrium - It is not growing warmer or colder
Seasonality
Refers to both the seasonal variation of the Sun’s position above the horizon and changing day lengths during the year
Seasonality
Seasonal variations are a response to changes in the Sun’s altitude
Seasonality
Day Length
Reasons for the Season
Revolution - orbit around the Sun
Rotation - turning on axis
Tilt - axis aligned at 23.5° from plane of orbit
Uneven Solar Heating
Unequal heating causes large scale movement (convection) of the Atmosphere
Air hearted in tropics expands and becomes less dense, rises to high altitudes Warm air gets pushed toward polesThen air becomes cool, becomes more dense, sinks to the surface
Coriolis EffectThe rotation of Earth on its axis deflects the moving air or water (or any moving object that has mass) away from its initial coarse.
To the right (clockwise)in Northern HemisphereTo the left (counterclockwise) in Southern Hemisphere
This deflection is called the Coriolis effect in honor of Gaspard Gustave de Coriolis, the French scientist who who first described this effect in 1835
Coriolis Effect
slow blowing winds will be deflected only a small amountstronger winds will be deflected morewinds blowing closer to the poles will be deflected more then winds at the same speed closer to the equatorSo The Coriolis force is zero right at the equator and strongest at the poles
Coriolis Effect
Coriolis VideoSimpson's ToiletAustralian Toilet
Atmospheric Circulation Cells
In reality, there are three major convection cells in each hemisphere
Hadley (or tropical) Cell (0-30°)Ferrel (mid-latitude) Cell (30-60°)Polar Cell (60-90°)
Winds Patterns
At the boundaries between atmospheric circulation cells, the air is moving verticallyEquatorial areas are calm and is called doldrums or ITCZ (Intertropical Convergence Zone)
Major wind patterns
Major wind patterns are:Doldrums• Calm equatorial areas, also called ITCZ
(Intertropical Convergence Zone)• Low pressure
Trade winds (easterlies) in Hadley cell• 0° to 30° N and S
Horse Latitude (subtropical high)• 30°N• High pressure
Major wind patterns
Major wind patterns continues:Prevailing Westerlies found in ferrel cells• 30° to 60° Latitudes
Polar front• 60°N and S Latitudes• Low Pressure
Polar easterlies found in the polar cells• 60° to 90°N and S Latitudes
Major wind patterns