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.