Atmosphere

Types of Rainfall

  • Types of Rainfall
    • Convectional Rainfall
    • Orographic Rainfall
    • Cyclonic Rainfall

Convectional Rainfall

  • Occurs when the surface of the Earth is heated up by the Sun.
  • Results in rapid upward movement of warm air which cools and condenses to form rain.

Orographic Rainfall

  • Caused by mountains blocking the path of moist air.
  • Windward side of the mountain receives rain as air rises and cools.
  • Leeward side receives less rain (rain shadow effect).

Cyclonic Rainfall

  • Associated with weather fronts and low-pressure systems (cyclones).
  • The lifting of warm air over cool air results in precipitation.

Atmosphere and Rainfall

  • Rainfall is a form of precipitation, which can be classified into various sizes:
    • Big Size: Hail
    • Small Size: Sleet (frozen drops)

Troposphere

  • Definition: The lowest layer of the atmosphere where weather phenomena occur.
  • Height:
    • Poles: 8 km
    • Equator: 18 km
  • Tropopause: Acts as the boundary between the troposphere and stratosphere.
  • Temperature Behavior: Generally decreases with altitude.
    • Lapse Rate:
    • 165 m - 1°C
    • 1 km - 6.5°C
  • Composition of Gases:
    • Nitrogen (78%)
    • Oxygen (21%)
    • Argon (0.9%)
    • Carbon Dioxide (0.036%)
    • Helium
  • Tropospheric Ozone: Harmful to the environment.

Heating Mechanisms of the Atmosphere

  • Conduction: Layer close to the Earth gets heated through conduction (vertical heat transfer).
  • Convection: Vertical transfer of heat following conduction.
  • Advection: Horizontal transfer of heat (e.g., a hot wind called Loo is a result of advection).

Insolation and Factors Affecting Temperature

  • Equator: Less insolation due to high cloud cover.
  • Tropics: More insolation due to lower cloud cover.
  • Aphelion: Less insolation; Perihelion: More insolation.
  • Factors affecting temperature:
    • Transparency of the atmosphere
    • Length of day
    • Tilt, Rotation
    • Position, Latitude, and Altitude

Albedo

  • Definition: The proportion of incident light or radiation that is reflected by a surface (e.g., ice caps/glaciers have high albedo).

Temperature Inversion

  • Definition: A layer in the atmosphere where air temperature increases with height, typically occurs under conditions of long winter nights, still air, and clear skies.

Stratosphere

  • Ozone Layer: Located between 30-35 km, protects from harmful UV rays.
  • Temperature increases with altitude.
  • Jet Planes: Fly in this layer.
  • Ozone Day: Celebrated on 16th September 1987.
  • Stratopause: Divides the stratosphere and mesosphere.

Mesosphere

  • Definition: The coldest layer of the atmosphere.
  • Meteorite Burns: Occur in this layer, as temperature decreases with altitude.

Thermosphere

  • Definition: The hottest layer, where temperature increases with altitude.
  • Known as the ionosphere due to the presence of ions, reflects radio waves.

Karman Line

  • Definition: Boundary between the Earth’s atmosphere and the exosphere, located at 100 km altitude.

Isotherm

  • Definition: Lines connecting points having the same temperature.

Water Distribution

  • Total Water Composition:
    • Water (97.2%)
    • Saline Water (2.8%)
    • Fresh Water (2%) which consists of:
    • Ice Caps/Glaciers (68.7% of total fresh water)
    • Ground Water (0.68%, 30.1% of total fresh water)
    • Lakes (0.4%)
    • Rivers

Water Cycle

  • Processes in the Water Cycle:
    • Water (liquid) → Water Vapor (gas)
    • Evaporation: Liquid water turns into vapor.
    • Water Vapor (gas) → Water (liquid)
    • Condensation: Water vapor cools and changes back to liquid.

Precipitation

  • Definition: Weather condition where things fall from the sky, such as rain, snow, or hail.
  • Humidity: Presence of water vapor in the atmosphere:
    • Absolute Humidity: Actual amount of water vapor present in the air.
    • Relative Humidity: Percentage of moisture relative to the maximum capacity of the air.

Dew Point

  • Definition: The temperature at which air becomes saturated with moisture, leading to condensation.

Types of Condensation

  • Dew: Moisture droplets that form as a result of condensation.
  • Fog: Dense collection of larger droplets that reduce visibility.
  • Mist: Collection of smaller droplets.
  • Frost: Deposits of white ice crystals, requiring no solid surface for condensation.

Clouds

  • Low-Level Clouds:
    • Nimbus: Rain-bearing, dark gray colored clouds that are opaque to sunlight.
    • Stratus: Layered clouds that do not produce rain, typically high-level clouds.
  • High-Level Clouds:
    • Cumulus: Flat base, cotton wool shaped, typically do not cause rain (4000-7000 m).
    • Cirrus: High altitude, feathery appearance, do not cause rain.