Abstract
On Jan. 15, 2022, the Hunga Tonga-Hunga Ha’apai (HT) eruption injected
SO2 and water into the middle stratosphere. Shortly after the eruption,
the water vapor anomaly moved northward toward and across the equator.
This northward movement appears to be due to a Rossby wave forced by the
excessive IR water vapor cooling. Following the early eruption stage,
persistent mid-stratospheric water vapor and aerosol layers were mostly
confined to Southern Hemisphere (SH) tropics (Eq. to 30°S). However,
during the spring of 2022, the westerly phase of the tropical
quasi-biennial oscillation (QBO) descended through the tropics. The HT
water vapor and aerosol anomalies were observed to again split across
the equator coincident with the descent of the QBO shear zone. This
split occurred because of the enhanced meridional transport circulation
associated with the QBO. Neither transport event can be reproduced using
MERRA2 assimilated winds.