1951-80 climatic normals

"The mandate to describe the climate was combined with guidelines established through international agreement. The end of a decade has been set by the World Meteorological Organization (WNO) as the desirable term for a 30-year period from which to calculate climatic conditions. The average value of a meteorological element over the 30 years is defined as a climatological normal. The normal climate helps in describing the climate and in determining climatic time trends by comparing the current 30-year period with earlier periods"--Page [1].

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