The Atmosphere: Climate and Weather

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The Atmosphere Climate and Weather

• John Todd
• 6 lecture mini-series

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Teaching Goals

• Stimulate your interest in this subject
• Basic understanding of main processes energy
  flow, air movement, water cycle, air pressure
• Present some of the terminology
• Demonstrate where climate/meteorology is useful
  across many disciplines

3
Your Lecturer

• PhD in atmospheric physics
• Interest in atmospheric transmission as an
  astronomer
• Air pollution control (Dept of Env)
• Lecturing Environmental Studies
• Interdisciplinary
• First time with this class

4
Jobs

• Competitive advantage
• Sailor
• Commodity trading
• Insurance
• Outdoor sports
• Assists understanding
• Sociologists
• Psychiatrists
• Medical science
• Fashion design
• Novelist

• Core Business
• Meteorologist
• Architect
• Engineer
• Pollution control
• Farmer
• Fisher
• Renewable energy

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Mini-Series on Weather and Climate

1. Atmosphere composition, temperature
2. Radiant energy flows, seasons
3. Global circulation
4. Water cycle
5. Weather
6. Human changes to atmosphere

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The Atmospherecomposition, structure and
temperature

• Chapter 3 of Christopherson
• Need to know
• Magnitude
• Changes with height
• Main gases

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The Atmosphere

• How thick?
• 10km, 480km, 32,000km
• How much?
• 5x1015tonnes
• 1 million t each!
• What is it?
• Nitrogen and oxygen
• H2O, CO2

12,700km
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Pressure

• Air behaves like any gas it is compressible,
  hence it becomes denser near the Earths
  surface.
• At sea level pressure of about 1kg/cm2
• Measured as hectopascal (1013 hPa) 1hPa1mb
• Drops about 1hPa per 10m near sea level
• By 16km down to 100hPa, by 32km down to 10hPa
• This means most air (75) is below 16km
• Mt Everest (8850m) 300hPa (i.e. 1/3 the oxygen)

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Temperature

• In troposphere (up to about 16km) temperature
  decreases with height by about 1oC every 150m.
• Gas laws reduce pressure ? lower temp.
• Important from pollution perspective
• Higher up more heating by sun

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Upper layers

• Exosphere (above 480km)
• Outer reaches, Earths influence detectable,
  essentially outer space, satellites
• Thermosphere (about 80 to 480km)
• Extremely thin atmosphere, aurora, meteors,
  temperature not as we would sense it
• Mesosphere (about 50 to 80km)
• Cooling because not much air to heat Noctilucent
  clouds

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Below 50km

• Stratosphere (about 18 to 50km)
• Temperature rise due to absorption of solar UV
• Ozone layer
• Little mixing from below
• Troposphere (below about 16km equator and 8km at
  poles)
• Well mixed
• Most clouds, water vapour , dust, pollutants
• Weather

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Composition in Troposphere
Gas Per cent Variable Rad. Active
Nitrogen 78
Oxygen 21 Yes (UV)
Water vapour up to 3.5 very yes
Argon 0.9
Carbon dioxide 0.035 yes yes
Neon 0.002
Helium 0.0005
Ozone 0.00006 yes yes
Hydrogen 0.00005
Nitrogen dioxide Trace yes
Krypton Trace
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Pollutants

• Waste from human activities
• Combustion
• CO, NOx, SO2, air toxics, ..
• Evaporation
• Volatile organic compounds, petrol, ..
• Direct discharge
• CFCs, odour, CH4,

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Inversions Prevent Dispersion
Prevents the air mixing upwards

• Inversion

TEMPERATURE
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Summary

• Atmospheric composition
• Mainly N2 and O2, some variable, some radiatively
  active, pollutants
• Pressure
• Air follows gas laws
• Temperature
• Decrease 6.5oC per km in troposphere
• Terminology
• Troposphere, etc., lapse rate, see handout

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Next Week

• RADIATION BALANCE
• Incoming solar radiation
• Outgoing long-wave radiation
• How this interacts with the atmosphere
• The seasons
• CHAPTERS 2 4 of CHRISTOPHERSON