A mixed scheme for subgrid-scale fluxes in cloud-resolving models

The benchmark simulation resolves a broad range of scales ranging from mesoscale organizations, gravity waves, individual clouds, down to energy-containing turbulent eddies. A spectral analysis shows that the vertical-velocity kinetic energy peaks at scales from hundreds of meters in the lower cloud layer to several kilometers higher up; these scales are typical grid sizes of today's CRMs.

The analysis also shows that a significant portion of the scalar and momentum fluxes in the benchmark simulation are carried by motions smaller than several kilometers, i.e., smaller than a typical grid resolution of CRMs. The broad range of scales of the benchmark simulation is split into two components: filter-scale (mimicking CRM-resolvable scale) and subfilter-scale (mimicking CRM-SGS) using filter widths characteristic of a typical CRM grid spacing.