Structure of atmosphere by Muhammad Fahad Ansari 12IEEM14
Composition and structure of ATMOSPHERE
Intro of the ATMOSPHEREComposition of the atmosphereVertical temperature structure
Composition of AirAir 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) 0.0325Comprise 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 THEATMOSPHERE GASES WATER VAPOUR DUST PARTICLES
THREE CATEGORIES OF ATMOSPHERIC COMPONENTS1) Constant gases Nitrogen, Oxygen Three Categories Argon Carbon dioxide •Constant gases Neon •Variable gases Helium •Particulates Krypton Hydrogen Ozone2) 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, smokeetc.
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 atmosphericcomposition… now a look at thestructure of the atmosphere…
Vertical Temperature Structure of the Atmosphere 4 layers Troposphere (sfc - ~ 10 km) Stratosphere (10 - 50 km) Mesosphere (50 - 80 km) Thermosphere (80 km ⇒)
The Troposphere sfc - ~10 km Height varies withlatitude and season(Why?) 70 - 80% of thetotal mass of theEarths 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.