atmosphere

• Atmosphere


  A layer of gases that surrounded the planet that makes the Earth suitable for living. It keeps us warm like a blanket.
• Layers of the atmosphere


  • Classified according to changes in temperature
• Composition of today's atmosphere

  • Nitrogen (mostly the product of volcanic eruptions)
  • Oxygen
  • Argon (an inert or noble gas)
  • Carbon dioxide (cycled through photosynthesis, respiration and burning of fossil fuels)
  • Ozone
• Variable gases


  Carbon dioxide and ozone, their quantity can change as a result of processes such as evaporation and transpiration and, in the case of ozone, because of varying rates of formation, pollution and seasonal change
• The natural balance of gases in the atmosphere is maintained by various cycles, for example the nitrogen cycle and carbon cycle
• Human activities can alter the composition of the atmosphere in many ways
• Ways human activities can alter the atmosphere


  • Carbon dioxide is added by burning fossil fuels and deforestation
  • Growing rice and keeping cattle both increase methane levels
  • We can also reduce some gases by afforestation or releasing ozone-destroying chlorofluorocarbons (CFCs)
• Troposphere


  • Temperature decreases with height because the warming effect of the Earth's surface through conduction and convection increases with altitude
  • The strength of gravitational pull and pressure decline with altitude
  • Wind speed increases with height
  • The top of this layer is called tropopause (where temperatures remain fairly constant)
  • It marks the upper limit to the Earth's weather and climate
• Stratosphere


  • This layer extends to nearly 50km above the Earth's surface
  • Pressure falls but temperature increases steadily with height this called a temperature inversion and caused by concentration of ozone which absorbs incoming UV radiation
  • This layer acts as shield against incoming meteorites , which burn out when they enter Earth's gravitational field
  • The upper limit of the stratosphere is called stratopause
• Mesosphere


  • This layer 50-80 km in height
  • Pressure decreases and temperature fall rapidly to below-80C because there is no water vapour, dust or ozone to absorb the incoming short-wave radiation
  • The upper limit of this layer is called mesopause
• Thermosphere


  • This layer is 80-1000km in height
  • Temperature rise rapidly to as high as 1500 °C because of the absorption of ultraviolet radiation by atomic oxygen.(free radical)
  • The upper limit of this layer is called thermopause
• Natural greenhouse effect


  A process that helps keep the Earth's surface and atmosphere warm
• Natural greenhouse effect


  1. The Earth receives incoming short-wave radiation (visible light UV) from the sun

  2. Half of this radiation is absorbed by the Earth's surface

  3. About 20% is absorbed by the atmosphere

  4. Around 30% is reflected by clouds and Earth's surface, back into space

  5. As the Earth's surface warms, outgoing long-wave radiation( infrared radiation) is emitted back into the atmosphere

  6. Greenhouse gases absorb some radiation and deflect it back to the Earth's surface
• Examples of greenhouse gases


  • Natural: water vapour, carbon dioxide, ozone, methane and nitrous oxides
  • Artificial: chlorofluorocarbon (CFCs)
• CFCs stay in the atmosphere longer than methane (1000 years compared with 12 years) so their impact continues into the future
• Atmospheric or air pollution

  Occurs when the atmosphere contains gases and substances in harmful amounts
• Pollutants


  The substances that causes atmospheric pollution
• Primary pollutants


  Pollutants that directly pollute the atmosphere
• Secondary pollutants


  Pollutants that form through chemical reactions of primary pollutants
• Smog


  Smoke and fog that occurs by burning of fossil fuels in industry, homes and vehicles provide particles that act as condensation nuclei for fog to form around
• Smog is a problem associated with industrial and urban areas and is more frequent during winter months as people use more heating
• Photochemical smog


  Involves chemical reactions induced by sunlight on certain pollutants, these reactions convert them into harmful substances such as ground level or troposphere ozone (bad ozone)
• Volatile Organic Compounds (VOCs)


  Chemicals that easily enter the atmosphere as gases, mainly from evaporation
• Examples of VOCs


  • Hydrocarbons (like methane)
  • Ammonium nitrate
  • Carbon monoxide (resulted from incomplete combustion)
• Temperature inversion


  A weather condition when air temperature increases with altitude, rather than decreasing
• Formation of temperature inversion


  1. During the day, the surface is heated due to long wave radiation

  2. On calm and clear night, the Earth surface cools very quickly, emitting radiation, cooling the air above it

  3. At higher altitude, the air doesn't cool as quickly , so this air becomes warmer than the air below it

  4. This layer of warm air is the inversion layer, that disrupts the regular convection currents
• Conditions needed for a temperature inversion

  • High air pressure (anticyclone), which causes upper air to sink
  • Calm conditions resulting from high pressure (wind disperse smog)
  • Valleys surrounded by steep-inside hills , which trap the smog
• Acid rain


  Precipitation with pH value of less than 7
• Formation of acid rain

  1. Burning of fuels in factories and power stations release sulfur dioxide and nitrogen oxide

  2. Vehicles emissions add nitrogen oxide

  3. When gases mix and react with water vapour in the atmosphere, they form weak solutions of acids (nitric and sulfuric acid), which can be moved by winds

  4. These solutions will eventually fall to Earth as acid rain
• Ozone


  A greenhouse gas that can be found in both the troposphere ('bad' ozone) and stratosphere ('good' ozone) but it is concentrated at a height of about 25 km in the stratosphere
• Formation of ozone layer


  Oxygen filtering from the top of the troposphere reacts under the influence of ultraviolet radiation to form ozone
• Ozone layer depletion


  • Ozone layer protects the Earth's surface from the Sun's harmful radiation, by absorbing incoming UV ultraviolet radiation from Sun
  • It is formed when oxygen (O2) filters from the top of the troposphere and reacts under influence of ultraviolet radiation to form ozone (O3)
  • It is continually formed, destroyed and replaced naturally, creating a dynamic balance, that is disturbed by human activities
• Ozone depletion by CFCs

  1. When CFCs reach the stratosphere, the ultraviolet radiation breaks them down, releasing chlorine

  2. Chlorine reacts with oxygen in a destructive process, breaking down the ozone molecule to chlorine monoxide and oxygen, depleting the layer and form a hole

  3. This hole allows harmful radiation to enter the Earth's atmosphere, so this lead to increase the level of UV radiation reaching the surface have been linked to increases in skin cancer and cataracts, and a reduction in immunity to disease
• Enhanced greenhouse effect


  Created by addition greenhouse gases to the atmosphere through human activities, leading to more heat retained in the atmosphere and increased temperature of the Earth's surface, causing global warming and climate change
• Impacts of atmospheric pollution

  • Smog: Irritation of eyes and throat, Respiration disease, like asthma, Fine particles carried into air lungs leading to lungs cancer, strokes and heart attacks, Breathing difficulties, Reduced ability of plants to make and store food by photosynthesis
  • Acid rain: Acidification of ground water, making the water undrinkable, Causes diarrhea and stomach upsets, Aluminum leached from the soil into the groundwater, Acidification of ground water damages tree roots, Crop yields decline, Nutrients like calcium are leached out of the soil, Fish die as acidity levels increase, Limestone buildings are chemically weathered
  • Ozone depletion: High levels of ultraviolet radiation cause sun burn, skin cancers, retina damage and cataracts, immune system can be suppressed, Extra ultraviolet radiation limits the reproduction of phytoplankton affecting the food webs, Changes in biochemical composition of some plant leaves make them less attractive as food, Melting of ice sheets, glaciers and permafrost cause a rise in sea levels
  • Climate change: Damage to low-lying countries from flooding, Forced migration as people lose their homes and farmland from rising sea levels, Loss of habitat and biodiversity, extinction of animals and plants if they cant adapt, Increased droughts could lead to desertification and famine, Sea- level rise to the loss of coastal land and increased erosion, Allow diseases to spread such as malaria
• Ways to manage atmospheric pollution

  • Reduction of carbon footprint
  • Reduced use of fossil fuels
  • Carbon capture and storage
  • Transport policies
  • International agreement and policies
  • CFCs replacement
  • Taxation
  • Catalytic converters
  • Flue-gas desulfurization
• Greenhouse effect


  The process that keeps Earth at a comfortable temperature for living things
• Earth is a comfortable place for living things due to the greenhouse effect
• Greenhouse


  A building with glass walls and a glass roof that traps the Sun's heat inside
• How a greenhouse works

  1. Sunlight shines through the glass

  2. Heat is trapped inside