Structure of atmosphere by Muhammad Fahad Ansari 12IEEM14

Composition and structure of ATMOSPHERE

Intro of the ATMOSPHERE

Composition of the atmosphere

Vertical temperature structure

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.

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.

COMPOSITION OF THE ATMOSPHERE

GASES WATER VAPOUR DUST PARTICLES

THREE CATEGORIES OF ATMOSPHERIC COMPONENTS

1) Constant gasesNitrogen, Oxygen Argon Carbon dioxide Neon Helium 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.

Three Categories

•Constant gases•Variable gases

•Particulates

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

We’ve now covered atmospheric composition… now a look at the structure of the atmosphere…

Vertical Temperature Structure of the Atmosphere

4 layersTroposphere (sfc - ~ 10 km)Stratosphere (10 - 50 km)Mesosphere (50 - 80 km)Thermosphere (80 km )

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.

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

The Mesosphere

Rarity of ozone

Rapid decrease in temperature

Mesopause is the coldest part of the atmosphere

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.

Aurorae or Polar Lights

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