Predictability experiments using a high- resolution limited-area model.

Abstract

Recently reported results indicate that limited-area mesoscale models with prescribed lateral boundaries do not exhibit the same predictability error growth as observed in large-scale (global) models. These results have been reanalyzed in greater detail. New methods of limited-area initialization and spectral analysis have been used. The new analyses indicate that several model properties act to restrict the growth of perturbations. These include: the projection of initial perturbations onto gravity waves which interact only weakly with other, more significant motions; the 'sweeping out' of errors by correct or perfect lateral boundaries; and the reduction of differences by subgrid dissipation. This last property suggests that there is a strong dynamical forcing of small scales by much larger scales, so that this forcing is only weakly affected by typical, small-scale perturbations in this model. - from Authors