Illustration of the different averages. Left panel: vertical cut through a part of the G2V simulation domain. Surfaces of constant optical depth (solid, red curves) and constant pressure (dashed, blue curves) are indicated; the underlying grey-scale image illustrate the density (normalised by the horizontal mean ⟨ϱ⟩_z). Right panel: run of the horizontally averaged temperature vs. averaged pressure in the G2V simulation for the different averages ⟨ · ⟩ _z (dotted, black), ⟨ · ⟩ _τ (red, solid), and ⟨ · ⟩ _p (blue, dashed); as a reference the position of some z and τ values is marked.