Ratios of the chemical to advection timescales for CH₄ (α = τ_chem∕τ_adv), for the zonal (top), meridional (middle), and vertical (bottom) components of the wind for the kinetics simulation of HD 209458b. We show a meridional-mean between ± 30° latitude for the zonal component, and slices at a longitude of 0° (i.e. the antistellar point) for the meridional and vertical components. The colour scale shows α, with blue colours corresponding to α > 1 and red colours corresponding to α < 1. The black contours show the α = 0.1, 1, 10 values. The fine structure shown in the plots is a reflection of regions where the wind velocity changes signs (e.g. eastward to westward) and the wind velocity approaches a value of zero over a very small region at the transition.