Resolving clouds in a global atmosphere model - A multiscale approach with nested models

Clouds are challenging to incorporate in global weather and climate models, since they involve processes on length scales much smaller than the typical simulation grid resolution. Therefore clouds are usually not resolved, but represented in a simplified way using so-called parametrization schemes. Accurate cloud modeling is important, since one of the largest remaining uncertainties in climate simulations is related to clouds and the strong effects of cloud feedback on the climate. We present our project on replacing the cloud parametrization scheme in a global weather model by another smallscale model which can explicitly resolve the cloud processes. This can be seen as a two-way nesting of a high -resolution model inside selected grid columns of the global model. The global weather model in our case is OpenIFS, a version of the ECMWF operational weather forecasting model. The high resolution model is DALES [1], a 3D large -eddy simulation code