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Topic 3: Introduction to Earth’s Atmosphere

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Topic 3: Introduction to Earth’s Atmosphere

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  1. Topic 3: Introduction to Earth’s Atmosphere • General Introduction:- Earth’s Atmosphere- Importance of the Atmosphere • Composition of the Atmosphere:- Common Atmospheric Gases- Greenhouse Gases- Atmospheric Particulates

  2. Topic 2: Introduction to Earth’s Atmosphere • Vertical Structure of the Atmosphere- Temperature Structure- Vertical Composition- Vertical Pressure Profile • Weather and Climate- What is Weather?- What is Climate?- Weather and Climate Controls

  3. The Earth’s Atmosphere • The atmosphere is a mixture of gases surrounding the earth • Atmospheric gases originate from gases released from the interior of the earth by volcanism and subsequently modified by plants and animals • Atmospheric gases are held in place by the force of gravity

  4. The Earth’s Atmosphere • Atmosphere may contain both solid and liquid impurities • Atmosphere is densest at sea level and decreases with increasing altitude • Hence, about 98% of atmospheric gases are found within 16 miles (or 26km) of the earth surface

  5. The Earth’s Atmosphere • Though earth atmospheric gases could be found as far away 6000 miles or 10,000 km • What is the actual extent of earth’s atmosphere? • Hint: What is the orbital altitude of the International Space Station (ISS)?

  6. The Earth’s Atmosphere • Average orbital altitude of ISS is 400 km • More than 50% of the mass of the atmosphere lies below 3.6 miles (5.6 km) • The three dominant gases are:- Nitrogen (78%)- Oxygen (21%)- Argon (0.93%)

  7. Importance of the Atmosphere • It is the main source of oxygen and other gases needed by plants and animals • It maintains water supply through the mechanism of the hydrological cycle • It prevents temperature extremes and functions as a great insulator

  8. Importance of the Atmosphere • It provides protection from cosmic or ultraviolet radiation • It provides protection from the impacts of small-sized meteorites by causing them to be incinerated through friction

  9. Principal Gases of Earth’s Atmosphere

  10. Principal Gases of Earth’s Atmosphere

  11. Greenhouse Gases in the Atmosphere • Greenhouse gases permit the passage of short-wave solar radiation • They disallow the passage of long wave infrared radiant energy from the earth surface from going back to space • Hence, radiant energy is allowed to accumulate to produce a warming effect or greenhouse effect

  12. Greenhouse Gases in the Atmosphere • Common greenhouse gases in the atmosphere include:- CO2(75% of global warming)-Chlorofluorocarbon (CFC) (20%)- Methane (15-20%)- Water Vapor- Ozone

  13. Greenhouse Gases in the Atmosphere • Producers of >50% of greenhouse gases are: - European Union- Brazil- China- Russia • Emission of greenhouses gases continues to rise with increasing growth in population

  14. Greenhouse Gases in the Atmosphere • Effects of global warming include:- more rains and longer growing season in high latitudes (Scandinavia, Canada, Siberia)- hotter summers and severe droughts in American Midwest- rise in sea level and flooding of coastal areas like Louisiana

  15. Loss of Coastal Land to Global Warming

  16. The Ozone Layer and CFC • Ozone (O3) is a triatomic oxygen • It forms a complete layer between 9 and 35 miles (15 – 55 km) above the earth surface • The ozone layer protects plants and animals from ultraviolet radiation in sun’s rays by absorbing the radiation

  17. The Ozone Layer and CFC • But ozone is a very fragile gas that can easily be destroyed naturally by:- sunspot cycle- oscillation of stratospheric wind- volcanic dust particles- effects of El Nino • Or human use of CFC in:- refrigeration & air-conditioning- aerosol sprays- foam & plastic manufacturing

  18. The Ozone Layer and CFC • Today, 5% more UV radiation gets to the earth surface than in 1969 • Up to 5% of the ozone layer has been destroyed over much of the United States • More rapid ozone depletion has been reported at the poles • Since 1975, Antarctic ozone hole has been found and appears to be persistent

  19. The Antarctic Ozone Hole Lowest Ozone level

  20. The Ozone Layer and CFC • Within the ozone layer, CFC becomes unstable and easily broken down by UV radiation • Causes CFC to set chlorine free • Chlorine pulls off oxygen atom from ozone to change it to an oxygen molecule and a chlorine monoxide molecule

  21. Destruction of Ozone By Chlorine from CFC

  22. The Ozone Layer and CFC • A free oxygen atom pulls an oxygen atom off chlorine monoxide molecule • Freed chlorine atom attacks another ozone molecule • One molecule of chlorine can destroy up to 100,000 molecules of ozone • Increase of CFC in the ozone layer is causing the rapid loss of the ozone layer

  23. The Ozone Layer and CFC Ozone depletion is more severe over the polar region because of:- extreme cooling of the poles in winter, especially the Antarctica, where whirling winter pattern (vortex wind) occur- the presence of stratospheric ice crystals forming polar stratospheric clouds increases the process

  24. The Ozone Layer and CFC - the ice crystals form surfaces for the accumulation of chlorine-based molecules and allowing spring uv radiation to trigger ozone depletion process Ozone depletion is less over Arctic than the Antarctica Key ozone depletion areas: Antarctica, Australia, mountainous regions of Europe, Central Canada and New Zealand

  25. The Ozone Layer and CFC Ozone depletion is highly correlated with increased levels of UV radiation Ground levels of UV radiation (or UV Index) are now established and useful for alerting on possible health risks

  26. The Ozone Layer and CFC • A number of efforts to protect the ozone layer include:- ban of the use of aerosol sprays in Canada and U.S. in 1978- the 1987 Montreal Protocol on Substances That Deplete Ozone Layer set a timetable to phase out all major ozone-depleting substances - ban of CFC use in 1996 & substitution with hydrochlorofluorocarbon (HCFC)

  27. The Ozone Layer and CFC • Since 2006, the loss of ozone is stabilizing • It is suggested in 2009 that the levels of ozone over the tropics would have become depleted to levels found in the poles by the year 2100

  28. The Ozone Layer and CFC • Some of the effects of exposure to ultraviolet radiation include:- causes skin cancer & damage to animal tissue- causes gene mutation- suppression of human immune system- causes eye problems including cataracts

  29. The Ozone Layer and CFC - causes marine deserts - causes drop in crop yield worldwide

  30. Air Pollution • Human activities have altered the composition of the atmosphere, especially in the cities • Natural sources of pollution include:- smoke from wildfires- ash from volcanic eruptions- windblown dust storms- plant pollen & salt particles in waves

  31. Air Pollution • There are two general types of air pollution:- Primary pollution: (pollutants, such as particulates, sulfur or nitrogen compounds, carbon oxides and hydrocarbons, released directly into the air)- Secondary pollution: (caused by chemical reactions in the atmosphere like photochemical smog)

  32. Primary Pollutants: Atmospheric Particulates • Sources of Atmospheric Particulates:- meteoric dusts- volcanic dusts and ash- wind blow surface materials- smoke from bush fires- salt crystals from sea sprays- particles of biological origin(pollen, spores, seeds & bacteria)- particles of human origins (factory smoke, automobile emissions, heating, etc)

  33. Primary Pollutants: Effects of Particulates in the Atmosphere • The effects includes:- reduction of solar energy reaching earth’s surface due to absorption and reflection of sunlight- optical effects on low-angled rays to produce colorful sunrise and sunset

  34. Primary Pollutants: Effects of Particulates in the Atmosphere - absorption of water (hygroscopic) and may form condensation nuclei- hazy conditions & atmospheric smog

  35. Primary Pollutants: Carbon Monoxide • Produced by the combustion of fossil fuels by automobile and industrial plants • Could be fatal if CO enters the bloodstream

  36. Primary Pollutants: Sulfur Compounds • May be natural in origin through releases by volcanoes or hydrothermal vents (Yellowstone National Park) • May be of human origin through the burning of coal and petroleum • SO2 may react in the atmosphere to form secondary pollutants like sulfur trioxide or sulfuric acid to form acid rain

  37. Primary Pollutants: Sulfur Dioxide • Sulfur dioxide is corrosive and a major lung irritant

  38. Primary Pollutants: Nitrogen Compound • Nitric oxide form through:- natural biological processes in water or soils- combustion in automobile engines • Nitrogen dioxide gives polluted air its yellow or reddish-brown color • Nitrogen dioxide may aid the production of smog by forming NO & leftover oxygen atom joins with O2 to form Ozone needed in photochemical smog

  39. Primary Pollutants: Nitrogen Compound • Nitric oxide may react with VOC to form peroxy-acetyl nitrate (PAN) • PAN may cause crop and forest damages

  40. Primary Pollutants: Photochemical Smog • Nitrogen dioxide and hydrocarbons (or volatile organic compounds – VOC) contribute to the formation of photochemical smog • Presence of ozone gives the smog its distinctive odor • Causes damage to vegetation, corroding building materials, damaging sensitive human tissues (eyes, lungs and noses)

  41. Vertical Composition of Atmosphere • The composition & percentage of gases in the lower 50 miles (80 km) of the atmosphere are homogenous & uniform • This is the homosphere and includes:- Troposhere- Stratosphere- Mesosphere

  42. Homosphere and Heterosphere of the Atmosphere

  43. Vertical Composition of Atmosphere • The composition and percentage of gases above 50 miles (80 km) are non-uniform due to little or no vertical mixing • This is the heterosphere • Gases in heterosphere are layered according to their molecular mass

  44. Vertical Composition of Atmosphere • The layered gases in the heterosphere:- Hydrogen (Top)- Helium- Oxygen- Nitrogen (Bottom) • Ozonosphere is a continuous layer of maximum ozone concentration between 9 and 30 miles (15 and 48 km)