Composition and Layers of the Atmosphere Mr. Silva Ag Earth Science
Composition of the Atmosphere• Nitrogen 78.08%• Oxygen 20.95%• Argon 0.93% (9300 ppm)• Carbon Dioxide 0.035% (350 ppm)• Neon 18 ppm• Helium 5.2 ppm• Methane 1.4 ppm• Ozone 0.07 ppm 3. Composition of the Atmosphere
Other Components of the Atmosphere• Water Droplets• Ice Crystals• Sulfuric Acid Aerosols• Volcanic Ash• Windblown Dust• Sea Salt• Human Pollutants 3. Composition of the Atmosphere
Aerosols Aerosols Any solid or liquid particle in theatmosphere.•Natural (e.g. dust) and human (e.g.soot) sources.•Can remain suspended for longperiods of time (days to weeks).•Contribute to cloud formation andprecipitation by acting ascondensation nuclei.
Aerosols: Saharan Dust StormDust particles are about 10 micro-meters in size (0.00001 meters). Roughly 1/10 thewidth of a human hair. Big ones settle out..
Structure (Layers) of the Atmosphere• Defined by Temperature Profiles• Troposphere – Where Weather Happens• Stratosphere – Ozone Layer• Mesosphere• Thermosphere – Ionosphere 4. Layers in the atmosphere are defined by temperature profiles
The Troposphere• Most dense• All weather takes place here
Troposphere• Heating of the Surface creates warm air at surface• Warm air rises, but air expands as it rises and cools as it expands (Adiabatic cooling)• Heating + Adiabatic Cooling = Warm air at surface, cooler air above• Buoyancy = Cool air at surface, warmer air above• Two opposing tendencies = constant turnover the atmosphere are defined by temperature profiles 4. Layers in
The Stratosphere• Dry• Absorbs ultraviolet radiation (UV)• Ozone layer is here• Ozone (O3) absorbs much UV C and UV B waves.
Stratosphere• Altitude 11-50 km• Temperature increases with altitude• -60 C at base to 0 C at top• Reason: absorption of solar energy to make ozone at upper levels (ozone layer)• Ozone (O3) is effective at absorbing solar ultraviolet radiation 4. Layers in the atmosphere are defined by temperature profiles
The Mesosphere• Coldest• Many meteors burn up here
Mesosphere• 50 – 80 km altitude• Temperature decreases with altitude• 0 C at base, -95 C at top• Top is coldest region of atmosphere 4. Layers in the atmosphere are defined by temperature profiles
The Thermosphere (Ionosphere)• Region of charged ions (positive) and electrons• Electrons are torn off atoms by sunlight of short wavelengths• Electrons don’t recombine easily because the distance between molecules is large at high altitudes and collisions are not frequent
Thermosphere• 80 km and above• Temperature increases with altitude as atoms accelerated by solar radiation• -95 C at base to 100 C at 120 km• Heat content negligible• Traces of atmosphere to 1000 km• Formerly called Ionosphere 4. Layers in the atmosphere are defined by temperature profiles
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