Extreme Heights of 15 January 2022 Tonga Volcanic Plume and Its Initial Evolution Inferred from COSMIC-2 RO Measurements

The Hunga Tonga-Hunga Ha'apai underwater volcano (20.57 degrees S, 175.38 degrees W) violently erupted on 15 January 2022. The volcanic cloud's top height and initial evolution are delineated by using the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)-2 radio occultation (RO) measurements. The bending angle (BA) anomaly over the Tonga volcanic plume (within 200 km of the eruption center) at 5:17 UTC on 15 January showed a prominent peak at higher stratospheric heights. The top of the BA anomaly revealed that negative to positive change occurred at similar to 38 km, indicating the first height where the RO line-of-sight encountered the volcanic plume. The BA anomaly further revealed an increase of similar to 50% at similar to 36.1 km, and confirmed that the volcanic plume reached above similar to 36 km. Furthermore, the evolution of BA perturbations within 24 h after the initial explosion is also discussed herein. From collocated RO profiles with the volcanic plume, we can find a clear descent of the peak altitude of the BA perturbation from similar to 36.1 km to similar to 29 km within 24 h after the initial eruption. The results from this study will provide some insights into advancing our understanding of volcanic cloud dynamics and their implementation in volcanic plume modeling.