Selected physical quantities in horizontal cross-sections through a single model snapshot (i.e. 3D model structure computed at a single instant in time) of the red giant model atmosphere after 146.8 h simulated time. The different columns show maps for the gas temperature (left), logarithm of gas pressure (middle), and the product of the absolute velocity and the sign of the vertical velocity component (right). Negative velocities are directed downwards/inwards (i.e. towards the stellar core) and positive velocities upwards/outwards. Each of these quantities is presented on planes of constant optical depth in the convection zone (top, log τ_Ross = 6.0), the photosphere (middle, log τ_Ross = 0.0), and the chromosphere (bottom, log τ_Ross = − 6.0). The streamlines in the right column follow the horizontal velocity field in the depicted plane.