Climatology Lecture 1

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ClimatologyLecture 1

• Michael Palmer
• Lectures available on
• www.atm.ox.ac.uk/user/mpalmer/

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Michael Palmer

• Geography _at_ CATZfinished 1997.
• Gap year 1998 Work Travel.
• PhD 1998 . Natural Variability of the (Lincoln)
  Climate System.

Department of Atmospheric Physics Room
119 mpalmer_at_atm.ox.ac.uk
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Climatology

• 12 Lecture Course
• Michaelmas Term 2001 (Weeks 1-4)
• 2 tutorials in College (typically 2 essays)

Lectures available on www.atm.ox.ac.uk/user/mpal
mer/
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What causes weather and climate?

• Heating
• Rotation

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Course Outline

• Heat and the Earths Atmosphere
• Vertical Motion Stability
• Horizontal Motion Winds
• The General Circulation Midlatitudes
• The General Circulation Tropics
• Variability of the General Circulation

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Heat and the Earths Atmosphere

• The basics of the atmosphere vertical structure
  and composition
• Heat transfer through radiation

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Heat and the Earths Atmosphere

• The basic structure of the atmosphere
• Heat transfer through radiation Electromagnetic
  spectrum Black body radiation Planck's law,
  Stefan-Boltzmann law, Wien's law
• Attenuation of radiation (absorption, scattering,
  reflection) what the atmosphere does with the
  suns heat
• The effective temperature of the earth life
  without greenhouse?
• Terrestrial radiation and the Greenhouse effect
• the radiation budget
• variation of the terms of the radiation budget
  diurnal, seasonal, spatial

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Atmospheric Composition

• Mechanical Mixture of GasesGas Volume (dry
  air)
• Nitrogen 78.1
• Oxygen 20.9
• Argon 0.9
• Also important trace gases
• CO2 370ppmv (1999)
• Water Vapour
• Ozone

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Heat and the Earths Atmosphere

• Heat can be transferred in 3 Ways Radiation Co
  nvection Conduction

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Heat and the Earths Atmosphere Radiation

• Nearly all the Earths energy comes from the Sun
• Sun nuclear reactor
• Earth receives less than one billionth of the
  Suns energy
• If the Earth could be viewed from the Sun, it
  would appear as a speck in the solar system, with
  the equivalent diameter of a 5p coin observed
  from a distance of 265m

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Radiation Total energy of phenomena relative to
total solar energy per day

• Solar energy received per day 1
• Strong earthquake 10-2
• Average Hurricane 10-4
• Krakatoa explosion 1883 10-5
• nuclear bomb 10-5
• summer thunderstorm 10-8
• tornado 10-11

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Heat and the Earths Atmosphere Radiation

• Electromagnetic SpectrumAll the wavelengths of
  radiant energy which can travel through the
  vacuum of space at the speed of light......
• (Only means for the planet to transfer energy to
  space)
• Characterised by wavelengths

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Wavelength
Low Frequency Long Wave
Amplitude
High Frequency Short Wave
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Wavelength
10 000 km
Long Radio Waves
1 000 km
100 km
10 km
1 km
AM Radio Waves
100 m
10 m
Short Radio Waves
TV
FM
1 m
Weather
100 mm
10 mm
Microwaves
Radar
1 mm
Infrared
Visible Light
Ultraviolet
X Rays etc
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Important Wavelengths for Climate

• Short wave radiation from the Sun0.48 microns
• Long Wave Radiation from the Earth/Atmosphere10
  micronsmeasurements in microns1 micron 10-6
  m 1/1000mm

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Why does radiation have characteristically
different wavelengths?
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Why does radiation have characteristically
different wavelengths?Radiation Laws
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• All bodies with a temperature gt 0 K emit
  radiation
• Wavelength characteristics determined by
  Radiation Laws Plancks Law Wiens
  Law Stefan-Boltzmann Law

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Plancks Law

• gives Radiation emitted by a body as a function
  of wavelength and temperature

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Plancks Curve SUN
10
107 Wm-2 µm-1
0
0.5
1.0
1.5
3.0
2.0
2.5
Wavelength (microns)
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Wiens Law

• Wavelength at which maximum emission of radiation
  occurs
• wavelength of maximum emission is inversely
  proportional to temperature
• hotter bodies emit shorter wavelengths
• cooler bodies emit longer wavelengths

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Plancks Curve SUN
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Peak Emission
107 Wm-2 µm-1
0
0.5
1.0
1.5
3.0
2.0
2.5
Wavelength (microns)
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Wiens Displacement Law

• Sun 2897/T 2897/6000 0.5
  micronsEarth 2897/288 10 microns

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Plancks Curve SUN
107 Wm-2 µm-1
Wavelength (microns)
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Stefan-Boltzmann Law

• The energy emitted by a body is directly
  proportional to the fourth power of the
  temperature of that body
• hot bodies emit a lot more radiation than cooler
  bodies
• emission 5.67x10-8 T4

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Plancks Curve SUN
10
107 Wm-2 µm-1
0
0.5
1.0
1.5
3.0
2.0
2.5
Wavelength (microns)
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Radiation Laws

• Apply to Black Bodies
• Theoretical bodies capable of absorbing all
  radiation incident upon them and re-emitting
  maximum possible radiation in all wavelengths and
  all directions
• Earth and the atmosphere do not behave as black
  bodies
• Emissivity ratio of emission of natural body to
  theoretical black body

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6000K
short wave
visible
99.99 energy
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6000K
short wave
visible
99.99 energy
288 K long wave infrared
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Readings for todays Lecture

• Barry, R.G. and Chorley, R.J. 1998 Atmosphere,
  Weather and Climate (7th Ed.) Chapter 2 (H679)
• Eagleman, J.R. 1980 Meteorology, the atmosphere
  in action Chapter 3.
• Henderson-Sellers, A. and Robinson, P.J. 1999
  Contemporary Climatology. Harlow Chapter 2 (H693)
• Lockwood, J.G. 1974 World Climatology. An
  Environmental Approach. London Edward Arnold,
  330pp. page 6-14.
• McIlven, J.F.R. 1992 Fundamental of Weather and
  Climate. Wokingham Van Norstrand Reinhold,
  457pp. Chapter 8.
• OHare, G. and Sweeney, J.1987 The atmospheric
  system (SoG H450)
• Briggs, D. et al 1997. Fundamentals of Physical
  Environment, Chapters 2-4.