Interaction between stratospheric Kelvin waves and gravity waves in the easterly QBO phase

  • A general circulation model is used to study the interaction between parameterized gravity waves (GWs) and large-scale Kelvin waves in the tropical stratosphere. The simulation shows that Kelvin waves with substantial amplitudes (∼10 m s−1) can significantly affect the distribution of GW drag by modulating the local shear. Furthermore, this effect is localized to regions above strong convective organizations that generate large-amplitude GWs, so that at a given altitude it occurs selectively in a certain phase of Kelvin waves. Accordingly, this effect also contributes to the zonal-mean GW drag, which is large in the middle stratosphere during the phase transition of the quasi-biennial oscillation (QBO). Furthermore, we detect an enhancement of Kelvin-wave momentum flux due to GW drag modulated by Kelvin waves. The result implies an importance of GW dynamics coupled to Kelvin waves in the QBO progression. Plain Language Summary: The variability of the tropical atmosphere at altitudes of about 18–40 km is dominated by a large-amplitude long-term oscillation of wind, the quasi-biennial oscillation, which has a broad impact on the climate and seasonal forecasting. This oscillation is known to be driven by various types of atmospheric waves with multiple spatial scales. Using a numerical model, this study reports a process of interaction between those waves on different scales, which has not been illuminated before. The result implies a potential importance of this process in the progression of the quasi-biennial oscillation. Proper model representations of these multiscale waves and tropical convection are required to simulate this process.
Author:Young-Ha Kim, Ulrich Achatz
Parent Title (English):Geophysical research letters
Place of publication:Hoboken, NJ
Document Type:Article
Date of Publication (online):2021/08/29
Date of first Publication:2021/08/29
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2022/03/14
Tag:Kelvin wave; QBO; gravity wave; quasi-biennial oscillation; wave interaction
Issue:18, art. e2021GL095226
Page Number:8
First Page:1
Last Page:8
Young-Ha Kim and Ulrich Achatz thank the German Federal Ministry of Education and Research (BMBF) for partial support through the program Role of the Middle Atmosphere in Climate (ROMIC II: QUBICC) and through grant 01LG1905B. Ulrich Achatz thanks the German Research Foundation (DFG) for partial support through the research unit Multiscale Dynamics of Gravity Waves (MSGWaves) and through grants AC 71/8-2, AC 71/9-2, AC 71/10-2, AC 71/11-2, and AC 71/12-2. Open access funding enabled and organized by Projekt DEAL.
Institutes:Geowissenschaften / Geographie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Licence (English):License LogoCreative Commons - Namensnennung-Nicht kommerziell 4.0