Heat and Atmospheric Circulation

Solar Energy Sun is a star of average size, temp. & color Sun captured 99.9% of nebula’s matter.1% formed planets, moons, comets, asteroids & debris Sun is only object able to sustain fusion

Solar Energy Transmission Energy top of atmosphere Earth’s distance from Sun results absorption of only 1/2 billionth of total energy Earth’s curved surface presents continually varying angle to parallel solar radiation

Uneven Solar Heating Equator receives 90° angle Other radiation arrives at more oblique angle 2.5 times more equator than poles in 1 year

Earth’s Heat Budget 51% on incoming solar energy is absorbed by Earth’s land and water surface Light striking land and sea are converted to heat Then, heat is transferred into atmosphere The 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 poles Then air becomes cool, becomes more dense, sinks to the surface

Coriolis Effect The 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 Hemisphere To 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 amount stronger winds will be deflected more winds blowing closer to the poles will be deflected more then winds at the same speed closer to the equator So The Coriolis force is zero right at the equator and strongest at the poles

Coriolis Effect Coriolis Video Simpson's Toilet Australian 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 vertically Equatorial 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