areal reduction factor

For areal rainfall of a given duration and return period, it is the ratio of the mean areal rainfall to the mean point rainfall for the same duration and return period in the same area.

The amount of precipitation of any type (including the liquid equivalent of frozen hydrometeors); usually taken as that amount measured by means of a rain gauge (thus a small, varying amount of direct condensation is included).

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.