Types and Distribution of Rainfall

  • The process by which, water from the atmosphere falls down on earth is known as precipitation. No change in state of water is involved in this process.
  • The main types of precipitation are rain, drizzle, snow, sleet, and hail.
  • Precipitation, which reaches ground in the form of liquid, is called rain.
  • Drizzle is the lightest form of precipitation.
  • Snowfall is the precipitation composed of ice crystals.
  • Sleet is a mixture of rain and snow.
  • Hailstones are frozen lumps of ice produced by thunderstorms.
  • The amount of rainfall depends on the moisture content of air.
  • Factors determining the rainfall are land and sea contrast, direction of prevailing winds, and presence of mountains.
  • The three main types of rainfall are convectional rainfall, orographic rainfall, and cyclonic rainfall.
  • Convectional rainfall occurs in summers or during hotter part of the day. It is very common in the equatorial regions and interior parts of the continents.
  • The chief characteristic of orographic rainfall or relief rain is that the windward slopes receive greater rainfall. Leeward slopes remain rainless and dry.
  • Cyclonic or frontal rainfall occurs in the area where cyclones occur.
  • The distribution of rainfall on earth depends on location and season. About 98% of earth’s surface receives rain in summer.
  • Regions of heavy rainfall are equatorial regions, eastern margins of continents in sub-tropical latitudes and western margins of continents between 40º and 60º latitudes.
  • Regions of scanty rainfall are Polar Regions, Western margins of continents in the trade wind belt and Eastern margins of continents in the westerlies wind belt.
  • Temperature and rainfall are the two most important elements of climate.
  • Factors affecting climate are latitude, land and sea contrast, altitude, wind direction, ocean currents, vegetation and, direction of mountain ranges.
  • The instrument used to measure the amount of precipitation is called rain gauge.

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