Observed Impacts of the Hunga Tonga Eruption on Stratospheric Temperature

The massive eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano in 2022 not only set a record for plume height, transporting aerosols and water vapor up to an altitude of more than 50 km into the mesosphere, it also resulted in a substantial stratospheric aerosol optical depth perturbation and previously unobserved hydration of the stratosphere. These disturbances are expected to persist for several years, affecting stratospheric circulation, composition, and dynamics. Our study investigates the stratospheric temperature signals of the HTHH eruption and their separation from the broader stratospheric variability. Using high-resolution satellite observations, we focus on the lower and middle stratosphere in the tropical and mid-latitudes for the period from January 2022 until June 2023. Within the early post eruption plume we find a pronounced temperature dipole structure that follows the vertical evolution of water vapor and aerosols. In addition, we find persistent long-lived cooling of up to -4 K in the middle tropical and subtropical stratosphere. The cooling pattern closely corresponds to the distribution of water vapor from the months post-eruption to mid-2023. We anticipate that this negative anomaly has implications for stratospheric circulation and composition, especially ozone levels. Our results provide new insights into the localized temperature changes shortly after the eruption and the short-term stratospheric climate signals. We are confident that our results will be useful for testing simulation results against observational analyses in future modeling studies.