Seamless turbulence parametrization across model resolutions

A pragmatic approach for representing partially-resolved turbulence in numerical weather prediction models is introduced and tested. The method blends a conventional one-dimensional boundary-layer parametrization, suitable for large grid-lengths, with a three-dimensional sub-grid turbulence scheme suitable for large eddy simulation. The key parameter for blending the schemes is the ratio of grid-length to boundary-layer depth. The method is tested in a range of simulations at different grid-lengths, demonstrating that the new turbulence parametrization improves the transition from unresolved to resolved turbulence as grid-length is reduced.