Overview of the entropy jump (top panel), maximal vertical rms-velocity below the surface (middle panel) and the density at the same height ρ_peak (bottom panel) vs. T_eff for [Fe/H] =  −2.0 and 0.0 (blue and black respectively). Models with the same gravity are connected with their respective functional fits (solid lines; see Appendix B). Note the inverse correlation between density and velocity.