Role of the QBO in modulating the influence of the 11 year solar cycle on the atmosphere using constant forcings

During solar maxima a weaker Brewer-Dobson circulation with relative downwelling, warming, and enhanced ozone occurs in the tropical lower stratosphere during QBO east conditions, while a stronger circulation, cooling, and decreased ozone exists during QBO west conditions. The net ozone increase during QBO east is the combined result of production and advection, whereas during QBO west the effects cancel each other and result in little net ozone changes.

Especially during Southern Hemisphere late winter to early spring, the solar response at polar latitudes switches sign between the two QBO phases and qualitatively confirms observations and other recent model studies. During a poleward downward modulation of the polar night jet and a corresponding modulation of the Brewer-Dobson circulation in time, solar signals are detected all the way down to the extratropical troposphere.

Possible limitations of the model experiments with respect to the fixed solar cycle conditions or the prescribed QBO phases, as well as the constant sea surface temperatures, are discussed.