The underwater Hunga Tonga-Hunga Ha’apai (HTHH) volcano erupted in the early hours of 15th January 2022 and injected volcanic gases and aerosols to over 50 km altitude. This eruption produced the largest global perturbation of stratospheric aerosols since the Pinatubo eruption in 1991 and the largest perturbation of stratospheric water vapour observed in the satellite era. Using offline radiative transfer modelling and observations, it was shown that the combined radiative effect of the water vapour and aerosol perturbations from the HTHH eruption produced a positive radiative forcing at TOA (top-of-atmosphere), leading to a net warming of the climate system, and a fast radiatively-driven plume descent, during the first month after the event (Sellitto et al., 2022). This was the first time a warming effect on the climate system and a plume sinking was linked to volcanic eruptions, which usually produce a transient cooling and a possible plume lofting. Building on these first analyses, we synthesise satellite, ground-based, in situ and radiosonde observations accumulated after 2 years since the eruption and we investigate the evolution of the radiative impacts at this temporal scale. As aerosols sedimented and the water vapour was entrained in the ascending branch Brewer–Dobson circulation, a  clear vertical separation of the stratospheric aerosol and the moisture anomaly were observed; the effect of this vertical separation on the TOA radiative forcing and localised atmospheric diabatic heating/cooling is analysed and discussed.

Reference:

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