Rossby mode frequency-shift time series due to variation in the solar rotation profile, plotted for m from 1 to 8 (top), and 9 to 15 (middle), calculated for each calendar year. The vertical grey dashed lines denote the positions of the maxima of solar cycles 23 and 24, to the nearest year. The vertical brown dashed line indicates the minimum between the two cycles. The smoothed sunspot number is plotted in the bottom panel.