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It is observed that the cube roots of precipitation amounts often are distributed normally. This is found to apply to data for stations ranging from arctic to tropic regions, from extremely wet to extremely dry regions, and for precipitation periods of one day to one year. For comparison, sets of data that have been analyzed by other methods are examined. Certain exceptions to and limitations on the generality of the normal distribution of the cube roots of precipitation amounts are pointed out. Ways of using this characteristic are discussed.

A method has been developed for estimating climatic expectancies of flood or drought from the mean and variance of a precipitation record. An interrelationship between the distributions of amounts from the various observing periods, e.g., hourly, daily, monthly, is demonstrated, so that any one of these records may be used to estimate the others. The method is based on the cube root normal distribution of precipitation and on an observed tendency for the distribution lines to be parallel. Graphs and tables are provided as an aid to making these estimates. The relationship between monthly, daily, and so forth amounts must be derived in some manner from the frequency spectrum of precipitation rates. This spectrum is shown to have the same profile as the theoretical spectrum for atmospheric pressure; thus the E(f) ∼ f−5/3 spectrum of kinetic energy regulates the relationship between precipitation distributions.

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