The nature of small-scale non-turbulent variability in a mesoscale model

Previous studies have shown that numerical diffusion plays a crucial role in the ability of mesoscale models to reproduce features similar to sub-meso motions found in observations, particularly in terms of spectral energy distribution. In this study, the impacts of surface heterogeneity and frequency of lateral boundary coupling are investigated as potential factors governing or modulating the occurrence of sub-meso motions. The spectral energy distribution after the reduction of model diffusion is analysed in detail. It is suggested that a combination of physical and numerical mechanisms is responsible for the final spectral shape.