GEO 125

Physical Geography

GLOBAL HEAT BALANCE

Heat versus temperature

• Heat is a form of energy
• Temperature is the measurement of heat

Electromagnetic spectrum

• Extremely short-wave radiation (1) x-rays, (2) gamma rays,   3) ultraviolet rays
• Visible light or short wave radiation (violet to red)
• Long-wave radiation (1) Infrared, (2) Microwaves, (3) Radio waves

Sun as a hot body

• Insolation (incoming solar radiation)
• Emits primarily extremely short-wave radiation and visible light

Constant amount of solar energy received at the earth's outer atmospheric shell as measured by the solar constant (2 langleys per minute)

Extremely short-wave radiation absorbed by the ozone layer thus primarily visible light passes through the atmosphere

Key processes in the solar radiation budget

• Radiation (ability of an object to emit energy)
• Absorption (ability of an object to assimilate energy)
• Reflection (ability of an object to repel light and measure as albedo)

Solar radiation budget

• A. Energy received at the surface (53%): 1) Direct radiation and 2) Diffuse radiation caused by scattering
• Energy not received at the earth's surface (47%): (1) Absorption by the ozone layer, dust, and clouds and  (2) Reflected by clouds

Earth as a cool body absorbs visible light and radiates long-wave infrared radiation

Heating of the troposphere

• Infrared (long-wave terrestrial radiation from the earth's surface
• Counter-radiation from the earth atmosphere (primarily clouds)

Variation in the amount of heat energy received at the earth surface

• Due to the variation of sun angle with latitude and season
• Depth of atmosphere that light must pass through

Global heat balance

• Energy surplus areas between 38 degrees north and south latitude
• Energy deficit areas poleward of 38 degrees north and south latitudes
• Transfer of heat energy by convection

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