Apparent solar cycle influence on long‐period oscillations in stratospheric zonal wind speed

The amplitude of the semiannual oscillation in stratospheric zonal wind speed, from rocketsonde data for 1960‐1978, appears to vary as a function of the solar cycle. The apparent solar cycle modulation influence is present at all latitudes, and is largest near the stratopause. The amplitude of the semiannual wave decreases up to 50% at all latitudes from solar maximum to minimum. During 1950‐1978, the period of the tropical quasi‐biennial oscillation at 30 mb varied inversely with the solar cycle. These results indicate care must be taken to consider solar‐cycle effects when comparing results for different periods of record or when estimating long‐term trends.