Response of the Quasi-Biennial Oscillation to historical volcanic eruptions

The impact of volcanic eruptions on surface climate is well-appreciated, but their in situ
impact on the Quasi-Biennial Oscillation (QBO) has received comparatively little attention. This study examines the QBO responses to Krakatoa and Pinatubo using five configurations of the NASA Goddard Institute for Space Studies (GISS) Model E2.2 and
MERRA-2 reanalysis. A dynamically consistent response is found in terms of static stability, zonal wind, and upwelling. Eruptions are found to bias the QBO towards a westerly state, such that the QBO period response depends upon the phase at the time of
eruption. The QBO does not have a clear amplitude response to an eruption, based on
these simulations. The underlying mechanisms appear not to be influenced to first-order
by interactive composition, sea surface temperatures, or long-term trends in CO2 and
ozone-depleting substances.