Calculated vertical distribution of abundances in the ultra-hot Jupiter WASP-33b and the hot Jupiters HD 209458b, HD 189733b, and WASP-39b. The solid lines correspond to the mean abundance, the shaded areas to the range around the mean ±σ, and the dotted lines to the abundances resulting from the unperturbed model. The panels on the left show the effect on the calculated abundances of the uncertainties on (photo)chemical kinetics, while the right panels correspond to the effect on the abundances of the uncertainty in K_zz.