Distribution of Precipitation


Distribution of Precipitation:

The average annual precipitation for the world as a whole is about 97.5 centimeters but the land receives lesser amount or rainfall than the oceans.

Different places of the earth’s surface receive different amount of annual precipitation and that too in different seasons.

 

Regions of Heavy Precipitation

The regions which receive over 200 centimeters of annual precipitation are included in this category.

These regions include equatorial coastal areas of tropical zone and west-coastal regions of temperate zone.

 

Regions of Moderate Precipitation

The regions which receive 100 to 200 centimeters of annual precipitation are included in this category.

These regions lie adjacent to the regions of heavy precipitation.

Eastern coastal regions of subtropical zone and coastal regions of the warm temperate zone are included in this category.

 

Regions of Less Precipitation

This category includes regions which receive precipitation between 50 to 100 centimeters.

These regions lie in the interior parts of tropical zone and eastern interior parts of temperate zone.

 

Regions of Scanty Precipitation

The areas lying in the rain shadows (leeward) side of the mountain ranges, the interior parts of continents, the western margins of continents along tropics and high latitudes receive precipitation less than 50 centimeters.

These regions include tropical, temperate and cold deserts of the world.

 

Precipitation is greatest in the equatorial region and decreases towards the poles.

Precipitation is heaviest in the coastal regions and decreases towards the interior of the continents.

Eastern coastal areas of tropical lands and western coastal areas of temperate lands receive heavy precipitation including equatorial regions.

Precipitation is very heavy on the windward side of highlands; very dry conditions prevail on the leeward side.

Coastal areas adjacent to cold currents are drier than coastal areas near warm currents.

The western margin of tropical land and polar region receive scanty rainfall.

 

Seasonal Variations

The equatorial regions and the western parts of temperate lands receive precipitation throughout the year.  The former receive conventional type of rain while the later gets cyclonic cum orographic type through westerlies.

About 2 per cent land areas of the world receive precipitation only in winter. These include Mediterranean regions of the world and Coromandel Coast of India.

Due to the seasonal shift in pressure and planetary wind systems, these regions (Mediterranean) do not get precipitation in summer as they come under sub-tropical high pressure belts and trade winds which become dry while reaching to the western margins of continents.

The remaining parts of the world receive precipitation only in summer.

It makes us clear that most parts of the world experience marked seasonal variation in precipitation.