Post on 04-Jan-2016
Composition of the Atmosphere
Carbon Dioxide
WaterVapor
0-4% by volumn
Variable Components of the atmosphere
Aerosol - fine solid or liquid particles suspended in the air (0.001 to 10 )m
Formation of Ozone
Ozone
Sustaining Ozone
Depletion of Ozone
3CFCl assuch CFCs
10-50 km (stratosphere)
23 CFClCl UVCFCl
ClO O Cl
23 O2Cl O ClO
Ozone Depletion
Ozone
The Ozone Hole
Ozone concentration drops sharply over Antarctica
The Ozone Hole
Polar vortex
Cold air-80C
1. Polar winter leading to the formation of circumpolar winds to develop the polar vortex which isolates the air within it. 2. Cold temperatures; cold enough for the formation of Polar Stratospheric Clouds. As the vortex air is isolated, the cold temperatures persist.
3. The chlorine reservoir species HCl and ClONO2 become very active on the surface of the polar stratospheric clouds. The most important reactions are:
232 ClNHO ClONO HCl
22322 ClOHHClHOCl HOCl;NHO OH ClONO
ClCl Cl2 h
Global Ozone Recovery Predictions
Protecting the atmosphere’s ozone layer
An international agreement known as the Montreal Protocol on substances that deplete the Ozone Layer was concluded under the auspices of United Nations in late 1987.
Pressure Decreases with Altitude
Pascal ,sm kg :unit 2-1-
Atmospheric pressure P: Force F acting on unit area due to the weight of the atmosphere.
mb10hPa10
Pa, 10 P
m 6.37x10 R
,ms 9.8 g
kg, 5.14x10M
,R 4
g MP
3 3
5
6
1-
18
2
Extent of the Atmosphere
International System (SI) of unitsor Metric system
1mb Pa 100 hPa 1
Temperature F C, K, :unit o
273.16 t T 32); (t 9
5 t 32; t
5
9 t FF
Thermal Structure of the Atmosphere
Thermal Structure of the Atmosphere
Temperature measures the average kinetic energy of molecules and atoms as they move.
Troposphere
Height of the tropopause varies with latitude
•Averaged Surface temperature is 288.16K, or 15C.•Decreases 6.5C per km up to 11 km (lapse rate)•Nearly all weather happens in this layer
Inversion: negative lapse rate. Temperature increase with height.
Stratosphere
The temperature at first remains nearly constant to a height of about 20km, and then, increases sharply until the stratopause.
Mesosphere
-90C (-130F)
The coldest layer of the atmosphere
Thermosphere
Contains only a minute fraction of the air mass. The temperature rises owing to theabsorption of very shortwave solar radiation by atoms of O and N.
Homosphere: The makeup of the air is uniform in terms of theproportions of its component of gases.(0 – 80/90 km)
Heterosphere:(from lowest to highest)N2, O, He, H.(80/90 km above)
Vertical Variations in Composition
Ionosphere: (80/90-400km) Molecules and atoms areionized by shortwave solar radiation into ions and electrons.
Aurora
Borealis from AlaskaAustralis from Space
Aurora results from the interaction between solar flare activity and Earth’s magnetic field. Solar flare are massive magnetic storms emitting fast-moving atomic particles (protons and electrons). As they approach the Earth, they are captured by Earth’s magnetic field, which guides them toward the magnetic poles. They impinge on the ionosphere and energize the atoms of oxygen and nitrogen molecules to cause them to emit light.
Structure of the AtmosphereTroposphere: Lowest 10 (mid-lat) to 16 km (tropics) . Where the weather happens. Tropopause is top boundary, ~75% of the atmosphereLapse rate: Temperature decrease with height in the Troposphere, standard = 6.5C per kilometer in the troposphere. Inversion: Negative lapse rate, temperature increases.Stratosphere: Temperature constant at about –55C then increases with height to 45-50 km where it is about –5 to 0 C. Warmed by O3 absorption (30-60 km) of solar UV. Stratopause is top boundary, ~ 99% of the atmosphereMesosphere: Temperature decreases with height reaching < -85C. Mesopause is top boundary, above 99.9% of the atmosphere at 80-85 km. Thermosphere: Above the mesosphere. Temperature increases greatly because air absorbs sunlight, but radiates inefficiently. Boundary of Space: 100 km Ionosphere: Overlaps Meosphere and thermosphere. Reflects AM radio at night but during the day extends lower (100 km 60 km) and absorbs most AM radio energy. Ozone layer: 10-50 km, produced by sunlight breaking up oxygen Protects us from solar UV.