2. Intro of the ATMOSPHERE
Composition of the atmosphere
Vertical temperature structure
3. Composition of Air
Air is a mechanical mixture of gases -
not a chemical compound
Constituent % by Volume
Nitrogen (N2) 78.08
Oxygen (O2) 20.95
Argon (Ar) 0.93
Carbon dioxide (CO2) 0.0325
Comprise 99.98% of total.
4.
5. Composition of Air (dry)
Constituent % by Volume
Nitrogen (N2) 78.08
Oxygen (O2) 20.95
Argon (Ar) 0.93
Carbon dioxide (CO2) 0.0325
Neon (Ne) 0.0018
Helium (He) 0.0005
Krypton (Kr) 0.0001
Ozone (O3) 0.0006
Hydrogen (H2) 0.00005
Trace gases are those with a concentration of <0.1%.
Important for life on earth.
7. THREE CATEGORIES OF ATMOSPHERIC COMPONENTS
1) Constant gases
Nitrogen,
Oxygen Three Categories
Argon
Carbon dioxide •Constant gases
Neon •Variable gases
Helium •Particulates
Krypton
Hydrogen
Ozone
2) Variable gases introduced by biological and industrial activities
(NO2, NO, SO2, etc.)
Water vapour is a variable gas. Varies between 1-4%.
3) Particulates are suspended particles of sea salt, dust, smoke
etc.
8. Particulate Matter
PM10, PM2.5, PM1, TSP, UFP
"Inhalable coarse particles" such as those found
near roadways and dusty industries, are larger than 2.5
micrometers and smaller than 10 micrometers in diameter.
Deposited in the lungs – breathing difficulties, trigger of
asthma
"Respirable Fine particles," such as those found in
smoke and haze, are 2.5 micrometers in diameter and
smaller. These particles can be directly emitted from
sources such as forest fires, or they can form when gases
emitted from power plants, industries and automobiles react
in the air. Enter the bloodstream – laid down as plaques in
the cardiovascular system
9. We’ve now covered atmospheric
composition… now a look at the
structure of the atmosphere…
10. Vertical Temperature Structure of
the Atmosphere
4 layers
Troposphere (sfc - ~ 10 km)
Stratosphere (10 - 50 km)
Mesosphere (50 - 80 km)
Thermosphere (80 km ⇒)
11.
12.
13. The Troposphere
sfc - ~10 km
Height varies with
latitude and season
(Why?)
70 - 80% of the
total mass of the
Earth's atmosphere and 99% of water vapour.
14. The Stratosphere
Stratified in temperature, with
warmer layers higher up and cooler
layers farther down
Heated from above
Conduction to below
Stability
No water vapour
Ozone layer – peak concentration of
ozone at approximately 25 km.
>90% of earth’s ozone
Filters all UV-A and much UV-B
Temperature maximises at ~50 km
Ozone begins to decrease rapidly
15. The Mesosphere
Rarity of ozone
Rapid decrease in
temperature
Mesopause is the
coldest part of the
atmosphere
16. The Thermosphere
Includes the ionosphere (to
around 600 km) and
exosphere (to around 10 000
km)
Auroras in the ionosphere
Exobase at top of ionosphere
(base of exosphere) – above
which particle collisions are
negligible
Air molecules are rare in this layer
Temperature can theoretically rise
to enormous levels.
BUT it would feel freezing.