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