An Evaluation of Gravity Waves and Their Sources in the Southern Hemisphere in the 7-Km GEOS-5 Nature Run

Gravity waves are important drivers of middle atmosphere circulation and transport. Due to computational limitations on resolution that will persist for the foreseeable future, they are currently parameterized in most climate models. However, gravity wave parameterizations remain poorly constrained by observations. High resolution models that resolve a good portion of the gravity wave spectrum can help provide guidance for gravity wave parameterizations. This study examines gravity waves and their sources in the Southern Hemisphere winter in a 7-km horizontal resolution global climate model. The GEOS-5 Nature Run is particularly suited for this study because it resolves much of the gravity wave spectrum. First, gravity wave amplitudes, wavelengths, and propagation directions are compared to those from observations. Next, the relationship between nonorographic gravity waves and sources in the Southern Hemisphere winter is examined. Finally, nonorographic gravity wave momentum fluxes are compared to orographic gravity wave momentum fluxes.