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Heat Transfer and the Atmosphere

Chapter 5

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Heat Transfer and the Atmosphere

Chapter 5

The transfer of heat is normally from a high temperature object to a lower

temperature object. Heat transfer changes the internal energy of both

systems involved according to the First Law of Thermodynamics.

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Heat Transfer and the Atmosphere

•1 Joule = 1 N*m = 1 kg m/s2 * m

•1 calorie is the heat energy needed to raise 1 gram of water by 1 degree Celsius.

•1 calorie = 4.186 Joules.

•1 Calorie = 1000 calories.

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Heat can be transferred by:• Conduction • Convection • Advection • Radiation

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Heat can be transferred by:

Conduction • Convection • Advection • Radiation

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is the transfer of heat within a substance, molecule by molecule

Conduction

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is the transfer of heat within a substance, molecule by molecule

Substance Heat Conductivity

Still air at 20 °C 0.023

Dry Soil 0.25

Water at 20 °C 0.60

Snow 0.63

Wet Soil 2.1

Ice 2.1

Granite 2.7

Iron 80

Silver 427

This is a listing of the heat conductivity of various substances:

Conduction

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Heat can be transferred by:• Conduction

Convection • Advection • Radiation

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is heat transfer by the mass movement of a fluid in the vertical (up/down)

direction. This type of heat transfer takes place in liquids and gases. This occurs

naturally in our atmosphere.

Convection

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Heat can be transferred by:• Conduction • Convection

Advection • Radiation

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Advection

• Advection is the transfer of heat in the horizontal (north/east /

south/west) direction. In meteorology, the wind transports heat by

advection. This happens all the time on Earth, heat is transported in many

ways.

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Radiation

• Radiation allows heat to be transfered through wave energy. These waves are called Electromagnetic Waves, because the energy travels in a combination of electric and magnetic waves. This energy is released when these waves are absorbed by an object.

The energy a wave carries is related to its wavelength (measured from crest to crest).

Shorter wavelengths carry more energy than longer wavelengths. Wavelengths are measured in terms of meters:

(millimeter) mm (micrometer) μm (nanometer) nm

(millimeter) mm (micrometer) μm (nanometer) nm

Note / All things with a temperature above absolute zero emit radiation.

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Electromagnetic spectrum

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• Absorbed : Increasing the internal energy of the gas molecules.

• Reflected : Radiation is not absorbed or emitted from an object but it reaches the object and is sent backward. The Albedo represents the reflectivity of an object and describes the percentage of light that is went back.

• Scattered : light is deflected in all directions, forward, backward, sideways. It is also called diffused light.

• Transmitted : Radiation not absorbed, reflected, or scattered by a gas, the radiation passes through the gas unchanged.

Emitted radiation can be

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The temperature of an object can tell us something The temperature of an object can tell us something

about the emitted radiation. about the emitted radiation.

The temperature of an object can tell us something The temperature of an object can tell us something

about the emitted radiation. about the emitted radiation.

• Stefan-Boltzmann law E = σT4

• Wien's law λmax = θ/T

θ is a constant equal to 2897 μm K

• Kirchhoff's Law says that good absorbers of a particular wavelength are

also good emitters of that wavelength, and poor absorbers of a

wavelength are also poor emitters at the same wavelength.