Constraints on a non-orographic gravity wave drag parameterization using a gravity wave resolving general circulation model

Abstract

The results of a T213L250 gravity wave (GW) resolving general circulation model (GWR-GCM) are used to constrain the GW source spectra of a non-orographic GW drag parameterization (GWDP) proposed by Hines. In this study, the following two constraints were placed on Hines's GWDP: 1) the launch level at which GW source spectra are specified, and 2) the GW-source spectra, that is, the seasonally varying geographical and azimuthal distribution of GW momentum flux and horizontal wind amplitude. Considering the importance of the lateral propagation of GWs, which is ignored in Hines's GWDP, the GW source spectra are prescribed using information from the GWR-GCM at 70 hPa, where the GWs have already propagated laterally some distance from their source regions. The GW-source spectra have significant geographical variations and anisotropy, reflecting source distribution and the effects of critical level filtering due to the background flows. Although the effects of the lateral propagation and intermittency of GWs are ignored, a T42L80 chemistry coupled climate model using the GWDP with the constraints developed in this study realistically reproduced the meridional structures of the zonal wind jets in the stratosphere and mesosphere.