Retrieval results. Left: retrieved best-fitting wind profiles for CO (red line) and HCN (blue line) measurements, using a fourth-order polynomial. Red and blue shadowed regions contain the ensemble of good fits according to the χ² criterion from Eq. (3). The semi-transparent grey rectangle indicates the unobservable northern latitudes. The solid black line shows the sixth-order fit to Voyager’s cloud-tracking winds (Sromovsky et al. 1993). Right: wind variations with altitude at the equator, 20°S and 70°S, both for our measurements and for a set of references in the literature (see Sect. 5 for details). Cloud-tracking winds from Fitzpatrick et al. (2014) and Tollefson & Pater (2018) are not shown at 70°S as they have uncertainties of about 1000 m s⁻¹. Winds from Fletcher et al. (2014) do not correspond to a direct measurement, but to the computed thermal wind equation applied to a reanalysis of the 1989 IRIS/Voyager data (dashed grey lines) and to 2003 Keck data (dashed cyan lines).