Fig. 7

Mean winds obtained as functions of local time and latitude for the entire period (December 2015–March 2017); zonal (a, c) and meridional (b, d) winds from 365-nm (a, b) and 283-nm (c, d) radiance. Local time (abscissa) is shown in descending order to preserve the longitudinal direction (east to the right). The local time is based on the initial image of tracking, and it is increased by 30 min corresponding to a westward shift of 7.5°. Stipples show where the indicated precision \(\left\langle {\varepsilon_{u} } \right\rangle\) (a, c) or \(\left\langle {\varepsilon_{v} } \right\rangle\) (b, d) is smaller than 2 m/s. Contours show the same precision measure at 4 and 8 m/s; color shading is not shown where it exceeds 10 m/s. Note that \(\left\langle {\varepsilon_{u} } \right\rangle\) and \(\left\langle {\varepsilon_{v} } \right\rangle\) do not include any effect from sampling biases (see the text). Vertical hatching indicates the standard deviation of 10-day-bin means at each latitude–local time grid (gray: < 4 m/s; light gray: 4–8 m/s; white: 8–12 m/s; none: > 12 m/s)