Articles | Volume 16, issue 11
Research article
13 Jun 2016
Research article |  | 13 Jun 2016

Tuning of a convective gravity wave source scheme based on HIRDLS observations

Quang Thai Trinh, Silvio Kalisch, Peter Preusse, Manfred Ern, Hye-Yeong Chun, Stephen D. Eckermann, Min-Jee Kang, and Martin Riese

Abstract. Convection as one dominant source of atmospheric gravity waves (GWs) has been the focus of investigation over recent years. However, its spatial and temporal forcing scales are not well known. In this work we address this open issue by a systematic verification of free parameters of the Yonsei convective GW source scheme based on observations from the High Resolution Dynamics Limb Sounder (HIRDLS). The instrument can only see a limited portion of the gravity wave spectrum due to visibility effects and observation geometry. To allow for a meaningful comparison of simulated GWs to observations, a comprehensive filter, which mimics the instrument limitations, is applied to the simulated waves. By this approach, only long horizontal-scale convective GWs are addressed. Results show that spectrum, distribution of momentum flux, and zonal mean forcing of long horizontal-scale convective GWs can be successfully simulated by the superposition of three or four combinations of parameter sets reproducing the observed GW spectrum. These selected parameter sets are different for northern and southern summer. Although long horizontal-scale waves are only part of the full spectrum of convective GWs, the momentum flux of these waves is found to be significant and relevant for the driving of the QBO (quasi-biennial oscillation). The zonal momentum balance is considered in vertical cross sections of GW momentum flux (GWMF) and GW drag (GWD). Global maps of the horizontal distribution of GWMF are considered and consistency between simulated results and HIRDLS observations is found. The latitude dependence of the zonal phase speed spectrum of GWMF and its change with altitude is discussed.

Short summary
Convection is an important source of atmospheric gravity waves (GWs). In this work, scales of convective GWs seen by limb sounders were first defined based on observed spectral information. Interactions of these waves with the background were considered. Long-scale convective GWs addressed by this approach showed significant importance in driving the QBO. Zonal mean of GW momentum flux and its vertical gradients are in good agreement with respective observations provided by limb sounders.
Final-revised paper