Time evolution of T_d (top), T_g (center), and T_ref (bottom) in a disk column at the fiducial r = 2 au, as compared to the final, relaxed state of T_ref. As in Fig. 4, we plot the τ_r = 1 optical surface in red and the ß = 1 cooling surface in white. T_ref, as well as T_d and T_g, rapidly relax to a smooth equilibrium disk inside the ß = 1 surface. Sound waves in the upper atmosphere, excited by the initial relaxation of the disk, are visible in Tg due to the slow cooling rate at high altitude.