Atmosphere

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Atmosphere

  • The Earth is surrounded by a blanket of air called the atmosphere.
  • It protects life from harmful sun rays and helps regulate temperature.

Composition of Air

  1. Nitrogen (78%) – important for plants (absorbed via bacteria).
  2. Oxygen (21%) – essential for respiration and burning.
  3. Other gases (1%) – carbon dioxide, argon, ozone, etc.
  4. Also contains water vapour, dust particles.

Structure / Layers of Atmosphere

  • Troposphere → closest to Earth; weather changes occur here.
  • Stratosphere → contains ozone layer; airplanes fly here.
  • Mesosphere → meteors burn here.
  • Thermosphere → very hot; contains ionosphere, reflects radio waves; auroras occur here.
  • Exosphere → outermost layer, merges into space.

Weather & Climate

  • Weather = day-to-day atmospheric condition.
  • Climate = average weather condition over long period (30+ years).

Elements of Weather & Climate

  • Temperature → measured by thermometer; decreases with height.
  • Air pressure → weight of air; measured by barometer.
  • Winds
  • Moisture: Water vapour in air.

Environmental Issues

  • Greenhouse effect → trapping of heat by gases like CO₂, methane.
  • Global warming → rise in Earth’s temperature.
  • Ozone depletion → thinning of ozone layer due to CFCs.
  • Cyclones → violent storms caused by low pressure areas.