Wave momentum flux ($\overline{u^{\prime }{w}^{\prime }}$)

The wave momentum flux ${\rho }_0\overline{u^{\prime }{w}^{\prime }}$ is the vertical transport of horizontal momentum by correlated velocity perturbations. Its vertical convergence exerts the mean-flow force $-{\rho }_0{\partial }_z\overline{u^{\prime }{w}^{\prime }}$.