What Is Appropriate Resolution for Simulations of Thunderstorms

Continuing advances in computer resources now allow researchers to simulate thunderstorms with very high resolution. For example, it is possible to simulate deep moist convection (including an entire mesoscale convective system) with grid spacing on the order of 100 m. It is natural to ask whether such high resolution is necessary, and at what point can simulations of convective processes be considered “well resolved”. Examination of the subgrid-scale turbulence parameterizations used in cloud models provides some guidance in the debate over adequate resolution. Although not widely acknowledged, the subgrid turbulence closures in most cloud models are taken directly from large eddy simulation (LES) models. Since the subgrid turbulence schemes from LES have been included in cloud models for decades, it is important to review whether these assumptions are valid for models with the commonly used grid spacing of order 1km.