Hayli Gubbi is one of the shield volcano systems in the Afar Rift of north-eastern Ethiopia. The eruption of this long-dormant volcano on 23 rd November 2025 generated a high-altitude SO 2 plume that spread across multiple continents within days. Using Sentinel-5P TROPOMI SO 2 observations, multi-altitude HYSPLIT forward trajectories, and GFS pressure-level winds, this study quantifies plume evolution, injection height, and transport pathways. Satellite observations revealed extremely high SO 2 column densities exceeding 180 DU near the source, followed by a rapid transformation from a compact Afar-region cloud to a continent-scale SO 2 filament exceeding 14,000 km within five days. The total SO 2 mass increased from 42 kt to a peak of 146 kt during the early expansion phase, followed by progressive decay associated with dispersion and chemical transformation. Trajectory sensitivity tests indicated an injection height near 14 km, placing the plume in the upper troposphere-lower stratosphere (UTLS). Persistent alignment with the subtropical jet controlled the rapid, coherent long-range transport. These findings highlight the dominant role of UTLS injection and subtropical jet dynamics in governing volcanic SO 2 dispersion and provide quantitative constraints for atmospheric transport modelling and hazard assessment.
Saleem et al. (Fri,) studied this question.