a) Grand average cross-correlation-function map from 2006 to 2012. The map represents the average ccf map of all seasonal ccf maps from Fig. D.1, thus consisting of 29 ccf maps in total. b) Global differential rotation signature. The dots are the correlation peaks per 5°-latitude bin and their error bars are defined as the FWHM of the corresponding Gaussian fits. The dashed line represents a fit using Eq. (5), whereas the solid line represents a fit using Eq. (6). The parameters for each fit are summarized in Table 5.