Turbulent flux

From Glossary of Meteorology

turbulent flux

Transport of a quantity by quasi-random eddies or swirls; the covariance between a velocity component and any variable.

For example, time series of potential temperature θ and vertical velocity w can be used to find the turbulent vertical kinematic heat flux, FH:
where there are N data points in each time series, i is the time-series data index, primes denote deviations from the mean (i.e., the turbulent gusts), and the overbar denotes an average over the whole time series.