Connection between the troposphere and stratosphere on a decadal scale

A decadal oscillation of the geopotential heights in the lower stratosphere, which is well-correlated with the 11-year solar cycle, is closely linked to changes of the temperature on the same time scale in the middle and upper troposphere, the temperature being higher on an average in the maxima than in the minima of the 11-year solar cycle. It appears likely that these changes in the tropospheric temperature are associated with changes in the Hadley circulation. It is well established that the decadal oscillation in the stratosphere is modulated by the Quasi-Biennial Oscillation in winter. We point out that the QBO also modulates the decadal oscillation at other times of the year, but that the effect of the modulation is then weaker because of the different wind regime in the stratosphere.