resultant wind

In climatology, the vectorial average of all wind directions and speeds for a given level at a given place for a certain period, such as a month.

It is obtained by resolving each wind observation into components from south and west, summing over the given period, obtaining the averages, and reconverting the average components into a single vector.
Compare Lambert's formula, wind rose, prevailing wind direction.

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.