Modeling the Radiative Forcing and Atmospheric Temperature Perturbations Caused by the 2022 Hunga Volcano Explosion

Abstract We model the radiative forcing (RF) of stratospheric sulfate aerosols (SAs) and water vapor (WV) clouds generated by the explosive eruption of the Hunga volcano on 15 January 2022, using the WRF‐Chem meteorology‐chemistry model. We inject 150 Mt of WV and 0.45 Mt of SO 2 at a height of 35 km. The resulting volcanic WV layer is cooled through thermal radiation and descends to 27 km in 2 weeks. After the eruption, the WV mixing ratio within the plume exceeds 30 ppmV and gradually reduces thereafter. Within 3 weeks, SO 2 is converted to SO 4 with a 1.0 μm global stratospheric aerosol optical depth (SAOD) of 0.0025. The SO 2 mass should be scaled to 0.73–1.46 Mt to fit the observed SAOD. The 6‐month average global mean net instantaneous RF (IRF) of volcanic SAs at the top of the atmosphere (TOA) reaches −0.381 W/m 2 for a 1.46‐Mt SO 2 emission. The negative WV net IRF at TOA is at least one order of magnitude in absolute value smaller than that from SAs. The WV IRF at the bottom of the atmosphere is negligibly small and cannot cause discernible long‐term effects on ocean temperature on its own. Cooling in the lower stratosphere within the WV plume exceeds −1 K, and the WV adjusted (to stratospheric temperature) RF (ARF) is positive at TOA and the tropopause but is overwhelmed by negative SA forcing. The patchy tropospheric temperature response does not show notable changes.