The Quasi-Biennial Oscillation Based on Double Gaussian Distributional Parameterization of Inertial Gravity Waves in WACCM Model

Abstract:

The adjustment of gravity wave parameterization associated with model convection has made possible the spontaneous generation of the quasi-biennial oscillation (QBO) in the Whole Atmosphere Community Climate Model (WACCM 4.0), although there are some mismatching when compared with the observation. The parameterization is based on Lindzen’s linear saturation theory which can better describe inertia-gravity waves (IGW) by taking the Coriolis effects into consideration. In this work we improve the parameterization by importing a more realistic double Gaussian distribution IGW spectrum, which is calculated from tropical radiosonde observations. A series of WACCM simulations are performed to determine the relationship between the period and amplitude of equatorial zonal wind oscillations and the feature of parameterized IGW. All of these simulations are capable of generating equatorial wind oscillations in the stratosphere using the standard spatial resolution settings. The period of the oscillation is associate inversely with the strength of the IGW forcing, but the central values of double Gaussian distribution IGW have influence both on the magnitude and period of the oscillation. In fact, the eastward and westward IGWs affect the amplitude of the QBO wind, respectively, and the strength of IGWs forcing determines the accelerating rate of the QBO wind. Furthermore, stronger forcing of IGWs can lead to a deeper propagate of the QBO phase, which can extend the lowest altitude of the constant zonal wind amplitudes to about 100 hPa.