Implementation of a gravity wave source spectrum parameterization dependent on the properties of convection in the Whole Atmosphere Community Climate Model (WACCM)

This article describes the implementation of a new source spectrum parameterization for convectively generated gravity waves in the Whole Atmosphere Community Climate Model, version 2 (WACCM2). This parameterization is active in the tropics and is interactive with the underlying convection. The gravity wave spectrum at each model grid point and time step is determined based on the convective heating depth, tropospheric wind, and the convective heating rate. This parameterization introduces more realistic spatial and temporal distributions of gravity wave activity and yields gravity wave characteristics related to the underlying wave source. We present the estimated gravity wave momentum flux phase speed spectra at 100 hPa as well as the gravity wave drag in the middle and upper atmosphere using the new source spectrum representation. We also show the effects of this more physically based parameterization on the structure of the stratospheric and mesospheric semi-annual oscillations of the zonal wind compared to a simulation with uniform gravity wave distribution. We conclude that the interaction of the gravity wave parameterization with tropospheric characteristics is a positive step toward a more physical representation of the middle and upper atmosphere.