Sensitivity of the quasi‐biennial oscillation simulated in WACCM to the phase speed spectrum and the settings in an inertial gravity wave parameterization

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: Chao Yu, Xianghui Xue, Jianfei Wu, Tingdi Chen, Huimin Li
• Format: Article
• Language: English
• Published: American Geophysical Union (AGU) 2017-03-01
• Subjects: quasi‐biennial oscillation; gravity wave parameterization; WACCM model
• Online Access: https://doi.org/10.1002/2016MS000824

Abstract The application of inertial gravity wave parameterization has allowed for the spontaneous generation of quasi‐biennial oscillation (QBO) in the Whole Atmosphere Community Climate Model (WACCM), although there is some mismatch when comparing with observations. The parameterization is based on Lindzen's linear saturation theory, modified to describe inertia‐gravity waves (IGW) by considering the Coriolis effect. In this work, we improve the parameterization by importing a more realistic IGW phase speed spectrum that exhibits a double peak Gaussian distribution calculated from tropical radiosonde observations. A series of numeric simulations are performed to test the sensitivity of QBO‐like oscillation features to the phase speed spectrum and the settings of parameterized IGW. All these simulations are capable of generating equatorial wind oscillations in the stratosphere based on standard spatial resolution settings. Central phase speeds of the “double‐Gaussian parameterization” affect QBO magnitudes and periods, and the momentum flux of IGW determines the acceleration rate of zonal wind. Furthermore, stronger IGW forcing can lead to a propagation of the QBO‐like oscillation to lower altitude. The intermittency factor of the parameterization also prominently affects the QBO period. Stratospheric QBO‐like oscillation with obvious improvements is generated using the new IGW parameterization in a long‐time simulation.