Chapter 4Atmosphere and Surface Energy

Balances

Robert W. ChristophersonCharlie Thomsen

Energy Essentials 

Energy and matter make up the universe. E=mc2

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 AtmosphereScattering: 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.

AbsorptionSelective, 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

Albedo

Figure 4.5

July and January Albedos

Figure 4.6

Satellite Measurements

Clouds and Albedo

Figure 4.7

Atmospheric Aerosols

Figure 4.8

Heat TransferDefinition:

the amount of internal energy of matter transferred between two objects due to temperature difference.

Air is a poor conductor of heat

ConductionMolecule-to-molecule transfer

ConvectionEnergy transferred by vertical movement of substance

AdvectionHorizontally dominant movement of substance

RadiationEnergy 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

Figure 4.15

Radiation Balance Equation:

Rn = Qsun(1-α) + Lair-Learth

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 Lair, warms the planet.

Surface Energy Balance Equation

Figure 4.15

Energy Balance Equation:

Rn = LE + H +G +A

On an daily or longer time basis

Rn = LE + H

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).

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

Figure 4.14

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

Inflows

outflow

Daily Radiation Curves

Figure 4.14

Simplified Surface Energy BalanceNET 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

Radiation Budgets

Figure 4.20

El Mirage, CA

Pitt Meadows,BC

The Urban Environment

Figure 4.21

Urban Heat Island

Figure 4.22

Urban Heat

IslandPilot

Project

Figure 4.23

Robert W. ChristophersonCharlie Thomsen

Geosystems 7eAn Introduction to Physical Geography

End of Chapter 4