Moisture factor

From Glossary of Meteorology

moisture factor

One of the simplest measures of precipitation effectiveness, given by Lang as
where P (cm) is precipitation and T (°C) mean temperature for the period in question.

This index recognizes only that as temperature increases, the effective moisture decreases due to greater evaporation. A number of greater refinements of this concept exist: De Martonne's index of aridity; Angström's humidity coefficient; Gorczyński's aridity coefficient; Thornthwaite's precipitation-effectiveness index and moisture index; and Köppen's formulas for outlining steppe climate and desert climate.

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