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Understanding Rainfall Frequency


Rainfall Frequency is just like it sounds, understanding how often it rains in a specific region.  But it is more than just how much rain, the concept focuses on exactly how often and how intense he rainfall is. This understanding is vital for agriculture and natural plant species that depend on rainfall instead of irrigation.  But this concept is also applicable for a location your are thinking about spending sometime in or moving too.


Think of two regions with equal amounts of rainfall.  At the end of the year they both have the same total inches in rainfall.  But what is really important is when it rains.  And when it does rain, how intense is it. One region may be subject to heavy rainfall in the summer but very little in the winter.  The other may have rainfall throughout the year.  So Rainfall Frequency is concerned with the pattern of the rainfall, not a yearly summation.


In 1922, W.G. Kendrew used this concept to form categories for regions.  While these categories were broad, detailed reports can be obtained for a specific area you are interested in.  W.G. Kendrew's categories, Rainfall Regimes, listed climates based on their general rainfall frequency.

  • Monsoon Regime

    • Heavy summer rainfall only to be followed by a dry winter.

  • Equatorial Regime

    • Two heavy rain seasons that sandwich a light rain season.  Yes there is no dry period, just different intensities of rainy seasons.

  • West Coast Regional Regime

    • Heavy rain during all seasons bu an emphasis on the fall and winter.

  • Tropical Regime

    • There are two sub regions within a Tropical Regime.

      • Two heavy rain periods sandwiching a long dry period (Near the equator)

      • One heavy rain period only to be followed bey a second rain period and then the dry period (Further from the equator, near the tropics)

  • Continental Interior Regime

    • A majority of the rain in the summer with a light rainfall during the winter.