Figure 5.

Simplified turbulence spectrum ϕ(κ) as a function of the horizontal wave number κ. The spectrum peaks at κ ∼ 1/l with l the length scale of the most energetic turbulent eddies (typically 1 km to 2 km over land [Kaimal and Finnigan, 1994]). Δ denotes the width of the spatial filter applied to the model equations. Mesoscale models typically operate at a filter width (Δ_meso) that is large compared to l, while large‐eddy simulations (Δ_LES) fully resolve the energy‐containing scale l. CPM climate simulations operate with grid spacings that fall into a range of scales termed as “terra incoginta.” The assumptions made in turbulence closures designed for the mesoscale limit and the large‐eddy simulation limit breakdown at these intermediate scales [Wyngaard, 2004, ©Copyright 2004 AMS].