The Radiation and Energy Balance

Radiation Balance

The radiation balance is the balance between incoming and outgoing components of radiant energy 

Shortwave Radiation Components

• Direct Shortwave Radiation (S) - Shortwave radiation penetrating directly to the surface without being affected by the constituents of the atmosphere.

• Diffuse Shortwave Radiation (D) - Shortwave radiation that has been scattered or diffused by constituents of the atmosphere (clouds, dust, etc.).

• Absorbed and Reflected Shortwave Radiation

  • The amount of radiation absorbed or reflected depends on the albedo of the surface.

  • Albedo is the proportion of radiation reflected from the surface, governed primarily by:

    • Surface color

    • Sun angle

Longwave Radiation Components

• Terrestrial radiation (L _(up)) - longwave radiation emitted by the earth's surface.

• Atmospheric Counter-radiation (L _(down)) - longwave radiation emitted by the atmosphere directed toward the surface

• Amount of L _(down) or L_(up) depends on the temperature of the emitting body.

• Net Radiation - is an accounting of incoming and outgoing radiation.

Q*=[(S+D)-((S+D)a)] + [L _(down)- L _(up)]

Energy Balance

• Energy balance refers to how energy is used in the earth - atmospheric system

Q* = LE + H + G

Energy Balance Components

Latent Energy Transfer (LE)

• LE is latent energy transfer

• Positive LE means evaporation is taking place.

• Negative LE means condensation is taking place.

Sensible Heat Transfer (H)

• Positive H means that energy is used to heat up the air.

• Negative H means the air is losing energy and cooling down.

Ground Heat Transfer (G)

• G + means that energy is transferred into the subsurface

• G- means that energy is transferred toward the surface.

Spatial Variation of Radiation and Energy Balance Components

• Insolation (Click here for map)

• Net Radiation (Click here for map)

• Sensible Heat

• Latent Heat

Can you....

• Explain why the sun angle varies at a place throughout the year.

• Describe how insolation intensity varies with sun angle.

• Describe how the earth's orbit effects seasons.

• Describe the spatial variation of the subsolar point throughout the year.

• Describe the three modes of heat transfer?

• Describe the components of the radiation balance?

• Describe the components of the energy balance and what they depend on?