4. Turbulent fluxes and the atmospheric surface layer

Questions to be answered

1. How do we compute the vertical turbulent flux from time or space series of \(u\) and \(w\)?

This lecture did not introduce new concepts, but explained the concept of turbulent fluxes from animations and data (so study the slides carefully!).

In short, we have shown that a time- or spatial series of \(u\) and \(w\) allows for the computation of the turbulent flux \(\overline{u^\prime w^\prime}\) in the following steps

1. Compute the means \(\overline{u}\) and \(\overline{w}\).

2. Subtract the means from the series to obtain \(u^\prime\) and \(w^\prime\).

3. Multiply the perturbations to obtain a series \(u^\prime w^\prime\).

4. Take the mean the series \(u^\prime w^\prime\) and obtain the flux \(\overline{u^\prime w^\prime}\).