Chapter 4
Atmosphere and
Surface Energy
Balances
Robert W. Christopherson
Charlie Thomsen

Energy Essentials
Energy and matter make up the universe.
E=mc 2
Matter: the “stuff” we see, smell and touch.
Energy: exists in various forms
Energy from the Sun (electromagnetic radiation)
Energy in Food (chemical)
The heat we feel
Energy can convert from one form to other forms (e.g?)
Definition: The capacity to do work

Forms of Energy
Kinetic Energy:
Energy associated with an object by virtue of its motion. e.g. Kinetic energy of a moving hammer can drive in a nail. The bigger the hammer and the fast the swing, the higher the kinetic energy.
Kinetic energy at atomic level is significant as atoms and molecules are continually vibrating.
Potential Energy:
To potential to do work e.g. suspended hailstone possess potential energy.

Solar Radiation Passing Atmosphere
Scattering: Air particles alter direction of light, without altering its wavelengths.
Raleigh Scattering scattering by atmospheric molecules (scattering particle’s diameter smaller than wavelength)
Selective: scattering strongly
Mie Scattering
Scattering by aerosols (scattering particle’s diameter equal or greater than wavelength.
Non-selective.
Reflection:
Deflection of photons from the objects that radiation falls upon.
Clouds reflect solar radiation, cooling the Earth.
Absorption
Selective, not all
Both atmospheric molecules and aerosols absorb solar radiation.

Refraction
Figure 4.4

Energy Pathways
Figure 4.1

Insolation at Earth’s Surface
Figure 4.2

Daily Net Radiation at TOA
Figure 2.11

Figure 4.5
Albedo

July and January Albedos
Satellite Measurements
Figure 4.6

Clouds and Albedo
Figure 4.7

Atmospheric Aerosols
Figure 4.8

Heat Transfer
Definition: the amount of internal energy of matter transferred between two objects due to temperature difference.
Air is a poor conductor of heat
Conduction
Molecule-to-molecule transfer
Convection
Energy transferred by vertical movement of substance
Advection
Horizontally dominant movement of substance
Radiation
Energy traveling through air or space without medium
Blackbody emits radiation according three radiation laws introduced early.

Heat Transfer
Figure 4.9

The Greenhouse Effect and
Atmospheric Warming
Atmosphere absorbs heat energy
A real greenhouse traps heat inside
Atmosphere delays transfer of heat from
Earth into space

Clouds and Forcing
Figure 4.10

Energy Budget by Latitude
Figure 4.13

Shortwave and Longwave Energy
Figure 4.11

Radiation Balance Equation
Radiation Balance Equation:
R n
= Q sun
(1-α) + L air
-L earth
Every term on the right hand side is radiation. This is the net energy available for all other biophysical processes. Many environmental problems can be explain with this equation.
1. Snow melting at high latitudes: lowers α, thus warms the planet.
2. Increase CO2, increase L air
, warms the planet.
Figure 4.15

Surface Energy Balance Equation
Radiation balance equation tells us how much energy is available, these energy can be converted into various forms depending on usage:
1. The evaporate water, storage in water vapor as latent heat (LE) .
2. Heat the ground surface and then passing to the surrounding air through convection (H) .
3. Heat the ground surface and then passing to lower layer through conduction (G).
4. Used by plants in photosynthesis and store energy in chemical bonds (A).
Energy Balance Equation:
R n
= LE + H +G +A
On an daily or longer time basis
Rn = LE + H
Figure 4.15

Earth–Atmosphere Radiation/Energy Balance
Figure 4.12

Energy Balance at
Earth’s Surface
Daily Radiation Patterns
Simplified Surface Energy Balance
The Urban Environment

Systems View of Daily Surface Energy
Reservoir: Total Energy Storage Nearly Ground
Inflows: Shortwave Radiation from the sun longwave from atmosphere
Outflow: Shortwave reflected
Longwave outgoing
Relationship:
R(t)=R(t-1)+ inflows -outflow outflow
Inflows
Figure 4.14

Daily Radiation Curves
Figure 4.14

Simplified Surface Energy Balance
NET R =
+SW (insolation)
–SW (reflection)
+LW (infrared)
–LW (infrared)
Figure 4.16

Global NET R
Figure 4.17

Global Latent Heat
Figure 4.18

Global Sensible Heat
Figure 4.19

El Mirage,
CA
Radiation Budgets
Pitt Meadows,
BC
Figure 4.20

The Urban Environment
Figure 4.21

Urban Heat Island
Figure 4.22

Urban
Heat
Island
Pilot
Project
Figure 4.23

End of Chapter 4
Geosystems 7e
An Introduction to Physical Geography
Robert W. Christopherson
Charlie Thomsen