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.