Figure 4. Vertical profile of the mean (a) zonal wind (westward wind) and (b) meridional wind obtained from UV tracking of Pioneer Venus (365 nm, produced from tables of Rossow et al. [1990]) in 1980 (green), 1982 (blue), and 1983 (purple) and from UV (380 nm, black) and IR (1.74 μ‎m, gray) tracking of Venus Express in 2006–2008 (produced from tables in Hueso et al., 2012). Here, positive zonal wind velocity indicates westward wind.