Turbulence Parameterizations and the Scaling Problem in Climate Models

The atmosphere and the ocean are turbulent fluids. Most of these turbulent processes are not resolved explicitly in climate models: the grid-resolutions are too coarse. However, the small-scale sub-grid processes (turbulence, convection, clouds) play a key role in regulating the large-scale climate. All these scales, from small-scale turbulence to planetary circulations need to be represented in climate models. Modern approaches to tackle this scaling problem in climate models are discussed. In particular new ideas to unify the representation of turbulence and convection in climate models, and to appropriately take into account the different physical scales and their interplay with the model grid-scale, are presented in some detail.