Fig. 8

Mean zonal winds between 20°S and 20°N averaged over each of 5-day bins in terms of local time (a, b) and longitude (c, d) from 365-nm (a, c) and 283-nm (c, d) images (m/s). For a given 5-day bin and local time–longitudinal grid point, the mean value is defined whenever daily averaged wind values are defined on any day in the 5-day period somewhere between the latitudinal range; thus, the representativeness is sometimes quite limited. Local time is defined as in Fig. 7, and the 3° longitudinal grid is converted into a 0.2-h local time grid in terms of nearest neighbors before computing 5-day means (a, b)