Index Terms
0340 Middle atmosphere dynamics
0341 Middle atmosphere: constituent transport and chemistry
0370 Volcanic effects
Introduction
The Hunga Tonga-Hunga Ha’apai (HT) (20.54°S, 178.3°W) erupted on Jan.
15, 2022, with a volcanic explosivity index (VEI) of 5, comparable to
Krakatoa eruption in 1883. As shown in Microwave Limb Sounder (MLS)
measurements (Millán et al., 2022, hereafter M22) and balloon sondes
(Vomel et al. 2022) a significant amount of water vapor was injected
into the southern hemisphere (SH) mid-stratosphere. HT also injected
SO2 which produced a distinctive aerosol layer (Taha et
al., 2022), although SO2 injection was modest for an
eruption of this size (Carn et al., 2022; M22). The MLS estimated water
injection was up to 146 Tg (M22) or ~10% of the total
stratospheric water vapor prior to the eruption. The water vapor and
aerosol plumes from the HT eruption have persisted in the southern
tropical mid-stratosphere for months, and the presence of water vapor
led to a stratospheric cooling of ~ 4° K in March and
April (Schoeberl et al., 2022, hereafter S22) due to the increased
outgoing IR radiation.
Trajectory simulations of the HT plume reported in S22 show that the
plume should remain almost entirely in the SH, yet observations of both
the aerosols and water vapor in the mid-stratosphere show the plume
extending to 20°N. Below we show that there were two events where water
vapor was transported across the equator into the northern hemisphere
(NH). The first event occurred within a month of the eruption. This
event also transported aerosols. The second event was associated with
descending QBO shear zone. Below we analyze both events, starting with
the QBO transport event.