Maps of the vertical velocity υ_z at constant geometrical depth z₀ = ⟨z(τ_R = 1) ⟩ (average level of the optical surface) for four of the six models. Upward motions are blue, downward motions are red, colour scales saturate at ± 2·υ_z,rms(z₀) (for values, see Table 1). Note that the horizontal scales are different (cf. Fig. 2).