Sensitivity of one-day predictions of meso-α and -β scales to model resolution

Abstract

Recent studies of mesoscale predictability by operationally used limited-area models raise questions related to the implications of variance exchange between the scales which are resolved and which are not resolved by a variable model grid. In this paper, we demonstrate the rô1e that model and initial data resolution plays in energy exchange between synoptic, meso-α, and meso-β scales. For that purpose, we consider 24-h evolution of barotropic channel flow on the β-plane. The number of modes investigated varies from 21 to 171 in the zonal direction and from 11 to 85 in the meridional direction. It is shown that dependence of nonlinear model interactions on spectral resolution varies with scales within the k^−5/3 mesoscale domain. A distinct region of scales in the meso-α and -β range is found to be insensitive, while surrounding modes are significantly affected by the choice of resolution. It is shown that the evolution of subsynoptic and meso-α modes depends upon variation of model resolution only, while the evolution of shortest meso-β modes is sensitive to variation of initial data resolution as well.