Temporal evolution of all the CHs under study. The length of the bars represents the lifetime from the first to the last observation near the central meridian. The profile displays the area evolution (scale in the left corner of the figure). The red triangle marks the peak in the CH area. If no clear central peak was detected, the mark was omitted. The number in front of the bars shows how many times the CH was observed passing the central meridian. The solar activity, approximated by the smoothed sunspot number (Source: WDC-SILSO, Royal Observatory of Belgium, Brussels), is shown in the background.