Evidence for solar signals in the mesopause temperature variability?

Planetary wave activity is further found to be modulated by a quasi-2-year oscillation. The modulation is strongest around 1994/1995 and lowest around 1988 and 2004, respectively. It is found that wave activity is mostly enhanced when the wind direction of the mean zonal wind of the equatorial quasi-biennial oscillation (QBO) reverses from westerly to easterly.