Earth's Atmosphere: Composition and Layers

• Atmosphere: the layer of gas surrounding a planet or other celestial body, held in place by gravity.

Composition

• Primarily nitrogen (N2, ~78%) and oxygen (O2, ~21%), with trace amounts of argon (Ar, ~0.9%), carbon dioxide (CO2, ~0.04%), and other gases.
• Water vapor (H2O) concentration varies significantly depending on location and temperature.
• Aerosols, tiny solid or liquid particles, are also present.

Atmospheric Layers

• Troposphere:
  • The lowest layer, extending from the surface up to about 7-20 km.
  • Contains most of the atmosphere's mass and water vapor.
  • Characterized by decreasing temperature with altitude.
  • Site of most weather phenomena.
• Stratosphere:
  • Extends from the tropopause (top of the troposphere) to about 50 km.
  • Contains the ozone layer, which absorbs harmful ultraviolet (UV) radiation from the sun.
  • Temperature increases with altitude due to ozone absorption of UV radiation.
• Mesosphere:
  • Extends from the stratopause (top of the stratosphere) to about 85 km.
  • Temperature decreases with altitude.
  • Meteors burn up in this layer.
• Thermosphere:
  • Extends from the mesopause (top of the mesosphere) to about 500-1000 km.
  • Temperature increases with altitude due to absorption of high-energy solar radiation.
  • The International Space Station orbits in this layer.
• Exosphere:
  • The outermost layer, gradually fading into space.
  • Extends from the thermopause (top of the thermosphere) outwards.
  • Characterized by extremely low density.
  • Atmospheric particles can escape into space from this layer.

Atmospheric Pressure

• Defined as the force exerted by the weight of the atmosphere per unit area.
• Decreases with altitude.
• Standard atmospheric pressure at sea level is about 1013.25 hectopascals (hPa) or 29.92 inches of mercury (inHg).

Atmospheric Temperature

• Varies with altitude and location.
• Influenced by factors such as solar radiation, latitude, and surface properties.
• Temperature profiles differ in each atmospheric layer.

Atmospheric Circulation

• Driven by uneven heating of the Earth's surface by solar radiation.
• Creates pressure gradients, leading to winds.
• Coriolis effect deflects winds due to the Earth's rotation.
• Hadley cells:
  • Tropical circulation patterns characterized by rising air at the equator, poleward flow, sinking air at around 30 degrees latitude, and equatorward flow near the surface.
• Ferrel cells:
  • Mid-latitude circulation patterns characterized by surface winds flowing towards the poles and rising air at around 60 degrees latitude.
• Polar cells:
  • Polar circulation patterns characterized by sinking air at the poles and equatorward flow near the surface.
• Jet streams:
  • Fast-flowing, narrow air currents in the upper troposphere.
  • Influenced by temperature gradients and the Coriolis effect.

Ozone Layer

• Located in the stratosphere, with the highest concentration of ozone (O3).
• Absorbs harmful UV radiation from the sun.
• Depletion of the ozone layer can lead to increased UV radiation reaching the Earth's surface, which can cause skin cancer, cataracts, and other health problems.
• Ozone depletion is caused by human-produced chemicals such as chlorofluorocarbons (CFCs).

Greenhouse Effect

• Occurs when certain gases in the atmosphere trap heat from the sun.
• Greenhouse gases include carbon dioxide (CO2), methane (CH4), and water vapor (H2O).
• The greenhouse effect is essential for maintaining a habitable temperature on Earth.
• Increased concentrations of greenhouse gases due to human activities can enhance the greenhouse effect, leading to global warming and climate change.

Air Pollution

• The presence of harmful substances in the atmosphere.
• Pollutants can be natural or human-caused.
• Major air pollutants include particulate matter (PM), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2).
• Air pollution can have negative impacts on human health, the environment, and the economy.

Atmospheric Phenomena

• Clouds: Visible masses of water droplets or ice crystals suspended in the atmosphere.
• Precipitation: Any form of water that falls from the atmosphere to the Earth's surface, such as rain, snow, sleet, and hail.
• Lightning: A discharge of electricity in the atmosphere.
• Thunder: The sound produced by lightning.
• Rainbows: Optical phenomena caused by the refraction and reflection of sunlight in water droplets.
• Auroras: Natural light displays in the sky, usually seen in high-latitude regions.

Explore Earth's atmosphere, a gas layer held by gravity. It's mainly nitrogen and oxygen, with trace gases, water vapor, and aerosols. Discover layers like the troposphere, where weather occurs, and the stratosphere, featuring the ozone layer.