EOMF-27. The evolution of aerosol and water vapor plumes from the Hunga Tonga-Hunga Haˈapai volcanic eruption

Abstract
Simulating a volcanic eruption’s impact on stratospheric aerosol presumes knowledge of its injection height and mass, plume composition, location, and atmospheric state variables. In situ measurements are key to validating these assumptions. Using measurements from the Tonga Rapid Response Experiment (TR2Ex) and subsequent Balloon Baseline Stratospheric Aerosol Profiles (B2SAP) soundings, we track the evolution of the aerosol and water vapor plumes following the Hunga Tonga-Hunga Haˈapai eruptions on January 13 and 15, 2022. Together, the Hunga Tonga-Hunga Haˈapai (HT-HH) eruptions (21 °S, 175 °W) are estimated to have injected very large quantities of water vapor (>100 Tg H2O) paired with a modest amount of sulfur dioxide (~ 0.49 - 0.56 Tg SO2; 0.25 – 0.28 Tg S) into the stratosphere. Whereas the typical e-folding lifetime of SO2 in the stratosphere is approximately one month, with its conversion gradually increasing the amount of sulfuric acid (H2SO4) aerosol, we observed large perturbations to stratospheric aerosol within a few days of the HT-HH eruption. Aerosol layers with the highest mass corresponded to regions of the plume with high water vapor mixing ratios. Assuming that particles were composed of H2SO4, in situ measurements of aerosol number and size can be used to determine vertically integrated aerosol mass and ambient stratospheric aerosol optical depth (sAOD). Together with OMPS sAOD (λ= 997 nm) and MLS H2O data, these in situ observations from La Réunion (21 °S, 55 °E) were used to calculate the total aerosol sulfur (S) mass (0.22 Tg S after 11 days) of the young plume and provide an estimate of the stratospheric SO2 e-folding lifetime in these wet conditions (~ 7.3 days), consistent with the initial estimate of SO2, the observed partitioning of S between TR2Ex SO2 (~20 %) and H2SO4 aerosol (~80 %), and recent modeling work. B2SAP water vapor and particle size distribution measurements from regular soundings from Lauder, NZ, Hilo, Hawaii, and Boulder, CO, as well as La Réunion in the subsequent months provide compelling evidence of gravitational sorting and settling of aerosol, as well as dilution and transport to higher latitudes in both hemispheres of the water vapor and aerosol plumes.