Model Generation of Spurious Gravity Waves due to Inconsistency of the Vertical and Horizontal Resolution

Abstract

Abstract The importance of the consistency between the vertical and horizontal resolution of numerical models has been suggested in recent studies. In this context, consistency means that the vertical scales that are physically related to the resolvable horizontal scales are also resolved. In this study, gravity waves produced in a hydrostatic primitive-equation numerical simulation of conditional symmetric instability (CSI) are shown to be produced by the inconsistency of the model resolution, where the physical relationship between the vertical and horizontal scales is determined by the slope of the narrow thermal structures (loosely termed “fronts”) produced by the CSI. The detailed examination of the spurious gravity waves in the numerical simulation and height perturbations in diagnostic experiments quantify the effects of this inconsistency in the resolution. It is shown that 1) spurious height perturbations of ∼1 m or less are produced, though these may be sufficient to cause significant gravity wa...