World distribution of rainfall
Also called: Precipitation regimes · Topic: Water in the Atmosphere: Humidity, Condensation, Clouds and Precipitation · NCERT: Class 11, Ch 10 "Water in the Atmosphere"
Meaning
The world distribution of rainfall describes where and when rain falls across the Earth. Some general rules apply:
- Rain decreases from the equator towards the poles.
- Coasts get more rain than continental interiors, and oceans get more than land.
- Between 35° and 40° N and S, east coasts are wetter and rain decreases westward.
- Between 45° and 65° N and S, the westerlies (winds blowing from the west) wet the west coasts first, and rain decreases eastward.
Over 200 cm a year falls in the equatorial belt, on the windward west coasts of cool temperate lands and on monsoon coasts. Under 50 cm falls in rain-shadow interiors and at high latitudes.
The timing of rain also varies. Equatorial lands get rain all through the year. Monsoon lands get it mostly in summer. Mediterranean lands get it mostly in winter.
Example
India shows both extremes. Mawsynram in Meghalaya gets about 11,000–12,000 mm of rain a year. Leh in Ladakh lies behind the Great Himalaya, in a rain shadow (the dry side of a mountain range). It gets only about 8.5 cm a year.
Don't confuse with
- Seasonal pattern of rainfall: This tells you which part of the year the rain falls in, not how much falls. For example, Mediterranean lands get most of their rain in winter, and monsoon lands get most of theirs in summer.