A Note on a QBO-Like Oscillation in a 1/5 Sector Three-Dimensional Model Derived from a GCM

Abstract

A QBO-like oscillation has been obtained in a simulation using the 1/5 sector three-dimensional model, with moist convective adjustment, derived from a preliminary version of the Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES) general circulation model. The basic structure of the oscillation is similar to that of the observed quasi-biennial oscillation (QBO). The amplitude of the oscillation is rather strong, about 30ms^-1, which is comparable to the observed oscillation (25ms^-1). However, the period of the oscillation is about 400 days, or half as long as that of the observed QBO in the lower equatorial stratosphere. Further, the height of the simulated oscillation is about 15km higher than that of the observed QBO.
From a preliminary analysis of the wave behavior, it is suggested that gravity waves are important in the simulation of the QBO-like oscillation.