A computationally efficient nonstationary convective gravity-wave drag parameterization for global atmospheric prediction systems

We extend the Chun-Baik parameterization of convectively forced stationary gravity-wave drag by adding a set of discrete nonzero phase speeds to incorporate the effects of nonstationary gravity waves. The extended scheme is computationally very efficient in comparison with full spectral parameterizations and eliminates the need to specify the wave source information at the interface level. We validate the extended parameterization against an explicit simulation of convection over a tropical ocean. The distribution of the cloud-top momentum flux for a typical range of phase speeds is roughly similar to those from more refined studies. It is shown that nonstationary waves should be included to reproduce the vertical variation of explicitly simulated momentum flux.