Impact of the Hunga Tonga volcanic eruption on stratospheric composition

The explosive eruption of the Hunga Tonga-Hunga Ha’apai (HTHH) volcano on 15 January 2022 injected more water vapor into the stratosphere and to higher altitudes than ever observed in the satellite era. Here, the evolution of the stratospherically injected water vapor is examined as a function of latitude, altitude, and time in the year following the eruption (February to December 2022), and perturbations to stratospheric chemical composition resulting from the increased sulfate aerosols and water vapor are identified and analyzed. The average calculated mass distribution of elevated water vapor between hemispheres is approximately 78% Southern Hemisphere (SH) and 22% Northern Hemisphere in 2022. Significant changes in stratospheric composition following the HTHH eruption are identified using observations from the Aura Microwave Limb Sounder satellite instrument. The dominant features in the monthly mean vertical profiles averaged over 15° latitude ranges are decreases in O 3 (–14%) and HCl (–22%) at SH midlatitudes and increases in ClO (>100%) and HNO 3 (43%) in the tropics, with peak pressure-level perturbations listed. Anomalies in column ozone from 1.2–100 hPa due to the HTHH eruption include widespread O 3 reductions in SH midlatitudes and O 3 increases in the tropics, with peak anomalies in 15° latitude-binned, monthly averages of approximately –7% and +5%, respectively, occurring in austral spring. Using a 3-dimensional chemistry–climate–aerosol model and observational tracer correlations, changes in stratospheric composition are found to be due to both dynamical and chemical factors.