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.