Muhammad Fahad Ansari 12IEEM14

1. Composition and structure of
ATMOSPHERE

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.

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.

6. COMPOSITION OF THE
ATMOSPHERE
GASES
WATER VAPOUR
DUST PARTICLES

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 ⇒)

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.

17. Aurorae or Polar Lights

18. THANK YOU