The Earths Global Energy Balance

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The Earths Global Energy Balance

• What is it?
• The difference in the flow of energy reaching
• the Earths surface and the flow of energy
• emitted by the Earths surface.
• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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Everything that has a temperature emits radiation
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Electromagnetic Radiation

• Hotter objects emit more energy at shorter
  wavelengths

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The Earths Global Energy Balance

• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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• Insolation over the Globe
• Insolation (incoming solar radiation)- is the
  flow of solar energy intercepted by an exposed
  surface
• Varies by latitude and by date

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• Insolation depends on the angle of the sun above
  the horizon.

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Insolation over the Globe
Figure 2.6, p. 57
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Insolation over the Globe

• Annual Insolation is greater at lower latitudes
  (closer to the equator)
• High latitudes receive much less solar energy
  (the annual insolation at the poles is about 40
  of the value at the equator

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World Latitude Zones
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The Earths Global Energy Balance

• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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Composition of the Atmosphere

• The atmosphere consist of air.
• What is Air? Air is a mixture of various
  gases
• Earths atmosphere extends about 10,000 KM above
  the earth
• 97 of the atmosphere lies within 30 KM of the
  Earths surface

Between 0 and 80KM the composition is pretty
uniform
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• Constant gases in the Troposphere
• Nitrogen 78 (converted by bacteria into a
  useful form in soils)
• Oxygen 21 (produced by green plants in
  photosynthesis)
• Carbon dioxide (CO2) (0.035)
• used by green plants during photosynthesis
  produced by respiration and burning of fossil
  fuels

Composition of the Atmosphere

• Argon 1

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Composition of the Atmosphere

• Other Variable atmospheric gases include
• Water vapor 0.1 - 4
• Methane (produced by cows, termites, swamps etc.)
• - Dust and particulates (from pollen, sea-salt,
  volcanic dust, soil, etc.)
• Ozone
• CFCs (entirely human-made gas)

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Composition of the Atmosphere
Ozone (O3) - Ozone in the stratosphere (35-55km)
absorbs ultra violet (UV) radiation
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Composition of the Atmosphere

• Ozone can be destroyed
• Chemicals (CFCs) created by humans contact Ozone
  oxygen and cause a chemical reaction turning O3
  into O2 (regular oxygen) this leaves less
  molecules to absorb UV rays
• If Ozone is reduced,
• UV absorption is
• reduced

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IG4e_02_p65
Every 1 decrease in global Ozone2 increase in
Ultraviolet radiation
Ozone holes due to aerosols (man made and natural)
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The Earths Global Energy Balance

• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• (Sensible Heat and Latent Heat Transfer)
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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Sensible Heat and Latent Heat
Sensible heat the quantity of heat held by an
object that can be sensed by touching or
feeling Conduction Direct transfer of heat or
energy from one object to another (in the
direction of decreasing temperature) Convection
When a warmer substance (water or air) moves into
the space of a cooler substance warming that
area.
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Sensible Heat and Latent Heat

• Latent heat (hidden heat)- heat that is used
  and stored in molecular motion when a substance
  changes state. The heat cannot be measured by a
  thermometer.

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Evaporation and Latent Heat

• Energy is required to overcome the molecular
  forces of attraction between particles of a
  liquid, and bring them to the vapor state, where
  attractions are minimal.
• To change liquid to water vapor, energy is
  absorbed into by individual molecules, these
  molecules get so energetic that they break the
  hydrogen bonds connecting them to other water
  molecules  Ultimately becoming molecules of
  water vapor.

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Latent Heat

• Each time water changes state, energy is absorbed
  or released.

Latent heat is important in moving large amounts
of energy from one region to another
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The Earths Global Energy Balance

• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• (Sensible Heat and Latent Heat Transfer)
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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The Global Energy System

• Energy Flows from the Sun to the earth and then
  back out into space
• Involves radiant energy flow AND energy storage
  and transport.
• Radiation is absorbed and diverted through
  scattering by dust/molecules, cloud reflection,
  albedo and more

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The Global Energy System
Albedo - percentage of solar radiation reflected
by any surface. - fresh snow 85-95 - dry
sand 35-40 - tropical forest 13 -
Earths average albedo 30
Light Surfaces (ice/snow)
Albedo values
Dark surfaces (pavement)
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The Earths Global Energy Balance

• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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Global Energy Budget

• Global energy budget of the earths atmosphere
  and surface must balance over the long-term
  (energy arrivingenergy leaving)
• Radiation/energy is reflected and absorbed by the
  atmosphere and the earth
• The earth loses energy through the emitting of
  long wave radiation, latent heat transfer and
  sensible heat transfer

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Global Energy Budgets of the Atmosphere and
Surface
49 of insolation direct radiation (radiation
that goes directly to Earths surface) 31 of
insolation reflected back to space
20 of insolation absorbed by the atmosphere
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Global Energy Budgets of the Atmosphere and
Surface

• Under clear skies, 80 of insolation may reach
  the ground
• Under cloudy skies, only 45 to 10 of insolation
  may reach the ground

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Greenhouse Effect
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The Earths Global Energy Balance

• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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Net radiation is the difference between incoming
and outgoing radiation
Net Radiation, Latitude and the Energy Balance
Incoming
Outgoing
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Net Radiation, Latitude and the Energy Balance

• Energy amount varies dependent upon latitudinal
  position
• Between 40N (and S) and the poles (90N and S)
  the net energy is negative
• Equatorially between 40N and 40S there is a
  positive net energy

Negative net energy
Positive Net Energy
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The Earths Global Energy Balance

• Radiation
• Insolation over the Globe
• Composition of the Atmosphere
• The Global Energy System
• Global Energy Budgets of the Atmosphere and
  Surface
• Net Radiation, Latitude and the Energy Balance

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