The Impact of 2022 Hunga Tonga‐Hunga Ha'apai (Hunga) Eruption on Stratospheric Circulation and Climate

Abstract

The Hunga Tonga‐Hunga Ha'apai (Hunga) volcanic eruption in January 2022 injected asubstantial amount of water vapor and a moderate amount of SO2 into the stratosphere. Both satelliteobservations in 2022 and subsequent chemistry‐climate model simulations forced by realistic Hungaperturbations reveal large‐scale cooling in the Southern Hemisphere (SH) tropical to subtropical stratospherefollowing the Hunga eruption. This study analyzes the drivers of this cooling, including the distinctive role ofanomalies in water vapor, ozone, and sulfate aerosol concentration on the simulated climate response to theHunga volcanic forcing, based on climate simulations with prescribed chemistry/aerosol. Simulated circulationand temperature anomalies based on specified‐chemistry simulations show good agreement with previouscoupled‐chemistry simulations and indicate that each forcing of ozone, water vapor, and sulfate aerosol from theHunga volcanic eruption contributed to the circulation and temperature anomalies in the SH stratosphere. Ourresults also suggest that (a) the large‐scale stratospheric cooling during the austral winter was mainly induced bychanges in dynamical processes, not by radiative processes, and that (b) the radiative feedback from negativeozone anomalies contributed to the prolonged cold temperature anomalies in the lower stratosphere (∼70 hPalevel) and hence to long lasting cold conditions of the polar vortex.