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EARTH'S RADIATION & ENERGY BALANCE

A. INTRODUCTION

Earth-sun relations affects insolation (incoming solar radiation)

Insolation isn't only form of energy affecting temperature patterns

Temperature affected by:

• radiant energy & heat energy

• balance between incoming and outgoing energy

• whether energy works to change temperature or to cause other kinds of changes

• characteristics of the earth's surface

Measuring energy

• calories: 1 cal = energy needed to raise temperature of 1 g of water 1^oC

• joules: 1 J = 4.2 cal

• energy flux: transfer of energy through a given area of space over a set interval of time

  • cal/cm²/min

  • W/m² (1 Watt = 1 J/sec)

B. FORMS OF ENERGY

Radiant Energy (electromagnetic radiation)

• temperature of a substance affects:

  • wavelength of radiation emitted

  • intensity (amount) of radiation emitted

• solar radiation and terrestrial radiation:

 

Heat (thermal) Energy

• temperature and heat

• specific heat and heat capacity

• forms of heat energy

  • sensible heat  

  • latent heat

C. RADIATION BALANCE

Net Radiation = Q* = total in - total out

Q* = (incoming shortwave - outgoing shortwave) + (incoming longwave - outgoing longwave)

Shortwave (Solar) Radiation (K)

• incoming shortwave =

Image source: NASA Visible Earth http://visibleearth.nasa.gov/view_rec.php?id=1683

= (S+D) S=direct beam solar D=diffuse (scattered) solar outgoing shortwave = reflected radiation = [a(S+D)] a=albedo: proportion of insolation reflected from a surface insolation reflected by atmosphere & earth's surface albedo varies geographically & temporally

• net shortwave

  •    

  • absorbed radiation (direct & diffuse)

Longwave (Terrestrial) Radiation

incoming longwave = radiation emitted by atmosphere determined by air temperature outgoing longwave =     radiation emitted by earth determined by surface temperature net longwave =

Radiation balance summary

• net radiation = amount radiant energy available to do work

• net radiation = total in - total out

D. ENERGY BALANCE

Energy gradient

• change in energy over space

• energy transfer is always from areas of higher to areas of lower energy, from warmer to cooler substances

Transfer mechanisms

• radiation

• conduction

• convection

Net radiation = Q* = H + LE + G

• H = sensible heat flux: energy used to change temperature of atmosphere  

• LE = latent heat flux: energy used to change state of water  

• G = ground heat flux: energy used to change temperature of subsurface

E. SUMMARY

Temperature patterns affected by:

• spatial & temporal imbalances in radiation & energy fluxes

• heat capacity and reflectivity of earth's surface

• type of work energy does (sensible or latent heat flux)