rainfall frequency

1. (Also called frequency curve.) The probability distribution specifying the exceedance probability of different rainfall depths for a given duration (such as 1 hour,

or a 24-hour day).
The exceedance frequency is often reported as a return period (in years), which is the reciprocal of the annual exceedance frequency.

1. The expected number of times, during a specified time period, that a given precipitation depth will be exceeded.

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.