Diabatic heating rates and early dispersion of the Hunga Tonga-Hunga Ha’apai plume 

The volcanic cloud generated by the 15 January 2022 eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano reached unprecedented altitudes in the modern observational record, with a maximum reported height of approximately 57 km, and an umbrella cloud at around 35 km. Over the first two weeks following the eruption, the stratospheric sulfate aerosol plume underwent a rapid descent, which was attributed to radiative cooling induced by a substantial water vapor anomaly [1, 2]. However, a comprehensive understanding of the initial subsidence of the plume—from its injection at about 35 km to its subsequent observation over La Reunion a few days later at around 29-30 km—is currently lacking. In this study, we use offline radiative transfer calculations to quantify the anomalous stratospheric heating rates resulting from a localized volcano-induced perturbation. We explore their sensitivity to various plume properties, including altitude and composition (e.g. in water vapor, ozone, and sulfate aerosols). Then, these radiative calculations are combined with Lagrangian trajectories using the ERA5 reanalysis model to reconstruct the early dispersion of the HTHH plume. The results are compared with the 3D plume structure inferred from satellite data (CALIOP, geostationary, GPS-radiooccultations, IASI-IMS) and Australian radiosonde observations.   References [1] Sellitto, P., Podglajen, A., Belhadji, R. et al. The unexpected radiative impact of the Hunga Tonga eruption of 15th January 2022. Commun Earth Environ 3, 288 (2022). https://doi.org/10.1038/s43247-022-00618-z [2] Legras, B., Duchamp, C., Sellitto, P., Podglajen, A., Carboni, E., Siddans, R., Grooß, J.-U., Khaykin, S., and Ploeger, F.: The evolution and dynamics of the Hunga Tonga–Hunga Ha'apai sulfate aerosol plume in the stratosphere, Atmos. Chem. Phys., 22, 14957–14970, https://doi.org/10.5194/acp-22-14957-2022, 2022. [3] Baron, A., Chazette, P., Khaykin, S., Payen, G., Marquestaut, N., Bègue, N., & Duflot, V. (2023). Early evolution of the stratospheric aerosol plume following the 2022 Hunga Tonga-Hunga Ha'apai eruption: Lidar observations from Reunion (21°S, 55°E). Geophysical Research Letters, 50, e2022GL101751. https://doi-org.insu.bib.cnrs.fr/10.1029/2022GL10175