Elements of the Sun; Solar Radiation

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Lecture 4 Heat Transfer and Energy Balance
Ch. 1, p. 5 See EarthsClimate_Web_Chapter.pdf,
p. 6-15
For more advanced reading materials, please see
http//www.geo.utexas.edu/courses/387h/ScheduleGPC
_detail.htm
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Forms of Heat Transfer in the Atmosphere and
Oceans
Radiation Conduction Convection Sensible
Heat Latent Heat
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Conduction
Conduction of heat energy occurs as warmer
molecules transmit vibration, and hence heat, to
adjacent cooler molecules. Warm ground surfaces
heat overlying air by conduction.
4
Convection
Convection occurs when hotter water rises and
cold water sinks, which helps distribute heat
energy.
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Convection of Sensible Heat (you can feel it!)
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The Development of Convection
Convection is heat energy moving as a fluid from
hotter to cooler areas. Warm air at the ground
surface rises as a thermal bubble expands,
consumes energy, and hence cools.
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Latent Heat
As water moves toward vapor it absorbs latent
(e.g. not sensed or hidden) heat to keep the
molecules in rapid motion.
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Latent Heat
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Latent Heat Energy for Storms
Latent heat released from the billions of vapor
droplets during condensation and cloud formation
fuels storm energy needs, warms the air, and
encourages taller cloud growth.
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Radiation, Convection and Conduction
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Warming Earth's Atmosphere
Solar radiation passes first through the upper
atmosphere, but only after absorption by earth's
surface does it generate sensible heat to warm
the ground and generate longwave energy. This
heat and energy at the surface then warms the
atmosphere from below.
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Incoming Solar Radiation (Insolation)
At the top of the atmosphere
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Processes That Affect Insolation
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Earths Radiation Budget (Global Average)
Earth reflects 30 directly back to space,
absorbs about 20 in the atmosphere, and absorbs
about 50 at the surface.
Earths lower atmosphere is warmed by radiation,
conduction, convection of sensible heat and
latent heat.
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The Global Energy Budget Driver of Atmospheric
Motion
A balance exists between the incoming solar
and outgoing longwave energy averaged over the
globe and the year
However, the tilt of the Earth means this
balance is not maintained for each latitude
DEFICIT
SURPLUS
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• To compensate for this energy
• imbalance, winds in the
• atmosphere and currents in the
• oceans transport cold air and
• water toward the equator
• About 1/3 of this transport
• occurs from the evaporation of
• tropical waters and subsequent
• transport into high latitudes,
• where it condenses and
• releases latent heat
• About 1/3 occurs from the
• poleward transport of warm
• waters by ocean currents
• The remaining 1/3 occurs from
• middle latitude cyclones and