Gravity wave momentum flux spectra observed from satellite in the summertime subtropics: Implications for global modeling

Abstract

The spectral distribution in terms of horizontal and vertical wavenumber is deduced for gravity wave (GW) momentum flux observations from space for the first time. The paper focuses on High Resolution Dynamics Limb Sounder (HIRDLS) observations in the subtropics and compares spectra over particularly strong deep convective forcing with a background inferred from regions of less momentum flux. The deep convective spectra are strongly enhanced at high horizontal wavenumbers over a wide range of vertical wavenumbers and phase speeds. The observations indicate that GWs generated by deep convection are an important contribution on top of the background spectrum due to other GW sources (at least about 20-30% on zonal average is from convective GWs). The implications for global modeling are discussed. © 2012. American Geophysical Union. All Rights Reserved.