Transcript The Atmosphere: Climate and Weather

The Atmosphere:
Climate and Weather
John Todd
6 lecture mini-series
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
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
Jobs
• Competitive advantage
• Core Business
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Meteorologist
Architect
Engineer
Pollution control
Farmer
Fisher
Renewable energy
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Sailor
Commodity trading
Insurance
Outdoor sports
• Assists understanding
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Sociologists
Psychiatrists
Medical science
Fashion design
Novelist
Mini-Series on Weather and Climate
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Atmosphere: composition, temperature
Radiant energy flows, seasons
Global circulation
Water cycle
Weather
Human changes to
atmosphere
The Atmosphere:
composition, structure and
temperature
• Chapter 3 of Christopherson
• Need to know
– Magnitude
– Changes with height
– Main gases
The Atmosphere
• How thick?
– 10km, 480km,
32,000+km
• How much?
– 5x1015tonnes
– 1 million t each!
• What is it?
– Nitrogen and oxygen
– H2O, CO2
12,700km
Pressure
• Air behaves like any gas – it is
compressible, hence it becomes
denser near the Earth’s surface.
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At sea level pressure of about 1kg/cm2
Measured as hectopascal (1013 hPa) [1hPa=1mb]
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)
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
A tm o s p h e ric te m p e ra tu re p ro file
120
TH E R M O S P H E R E
100
M e s o p a us e
M E S OS P HE RE
60
O zo ne la ye r
S tra to p a us e
40
S TR A TO S P H E R E
20
Tro p o p a us e
TR O P O S P H E R E
-1 0 0
-8 0
0
-6 0
-4 0
-2 0
d e g re e s C
0
20
40
Altitude km
80
Upper layers
• Exosphere (above 480km)
– Outer reaches, Earth’s 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
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
A tm o s p h e ric te m p e ra tu re p ro file
120
TH E R M O S P H E R E
100
M e s o p a us e
M E S OS P HE RE
60
O zo ne la ye r
S tra to p a us e
40
S TR A TO S P H E R E
20
Tro p o p a us e
TR O P O S P H E R E
-1 0 0
-8 0
0
-6 0
-4 0
-2 0
d e g re e s C
0
20
40
Altitude km
80
Composition in Troposphere
Gas
Per cent
Nitrogen
78
Oxygen
21
Water vapour
Argon
up to 3.5
Variable
Rad. Active
Yes (UV)
very
yes
yes
yes
yes
yes
0.9
Carbon dioxide
0.035
Neon
0.002
Helium
0.0005
Ozone
0.00006
Hydrogen
0.00005
Nitrogen dioxide
Trace
Krypton
Trace
yes
Pollutants
• Waste from human activities
• Combustion
– CO, NOx, SO2, ‘air toxics’, …..
• Evaporation
– Volatile organic compounds,
petrol, …..
• Direct discharge
– CFCs, odour, CH4, ……
Inversions Prevent Dispersion
• Inversion
Prevents the air mixing
upwards
TEMPERATURE
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
Next Week
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RADIATION BALANCE
Incoming solar radiation
Outgoing long-wave radiation
How this interacts with the atmosphere
The seasons
• CHAPTERS 2 & 4 of CHRISTOPHERSON