Rainfall

• Rainfall is the amount of water that falls from the atmosphere in a certain period It is the main type of precipitation
• There are 3 types of rainfall:

  1. Relief rainfall
  2. Convectional rainfall
  3. Frontal rainfall
• Relief or orographic rainfall is formed in the presence of a mountain or hill barrier and a neighboring water body. The water body is heated up by the sun and loses its water vapor through evaporation. Wind blows over the water and carries the moisture up the mountain as warm moist winds to the windward side. This warm moist air reaches dew point, it cools and solidifies to form clouds through condensation. The clouds get saturated with moisture and falls as rainfall. The windward side experience rainfall but the leeward side does not
• Convectional rainfall occurs over a large body of water. The water body is heated by the sun, loses moisture through evaporation Surrounding trees lose that moisture through transpiration. The warm moist air rises and on reaching dew point, the moisture undergoes condensation to form clouds. The clouds get saturated with moisture and falls as rainfall.
• NOTE:

  • Convectional rainfall is highly accompanied by lightning and thunderstorms
  • It mostly occurs in the afternoon
• Front rainfall, also called cyclonic rainfall is formed by the influence of air masses. A cold air mass is dry and heavy while a warm air mass is moist and light. The meeting point of the warm and cold air masses meet is called a front. When two air masses meet, the warm air is forced upwards and the cold air is forced downwards due to the different densities and temperatures. The moisture rises and on reaching dew point it undergoes condensation. The clouds get saturated and fall as rainfall along the front.
• An air mass is a large volume of air with the same temperature and humidity