Time and spatial averages of ν_eff (red squares) and η_eff (blue circles) for the simulations h24, h16, h12, h8, and h6 as function of grid spacing h (left panel); for the simulations h8, h8ν_H4, h8ν_H8, h8ν_H12, and h8ν_H16 as function of ν_H (centre panel); and for the simulations h8, h8η_H4, h8η_H8, h8η_H12, and h8η_H16 as function of η_H (right panel). The dashed and dotted black lines in the left panel are proportional to h² and h, respectively, whereas the dashed black lines in the centre and right panels are proportional to ν_H and η_H, respectively. The error bars denote one standard deviation computed over time and vertical direction z.