Vertical distributions of the abundances of CH₄, NH₃, CO₂, and HCN at the evening (solid lines) and morning (dashed lines) limbs, as calculated by the zonal wind model (thick lines) and by the vertical mixing model (thin lines). Note that abundances above the 10^-4–10^-5 bar level may not be reliable due to the lack of photochemistry in our model and, in the case of the zonal wind model, to a likely change in the circulation pattern.