Strength of TROPOMI satellite observations in retrieving hourly resolved sources of volcanic sulfur dioxide by inverse modeling

Volcanic eruptions release sulfur dioxide (SO ₂), impacting air quality, ecosystems, and aviation. To comprehensively assess these effects, high-temporal-resolution SO ₂ emission data is crucial. In this study, we use an inverse modeling procedure, assimilating SO ₂ column measurements from TROPOMI and OMPS low-Earth orbit satellites into an Eulerian chemistry-transport model. This procedure allows us to derive precise hourly SO ₂ mass flux and injection heights. TROPOMI, with its exceptional spatial resolution, excels at detecting short-lived, concentrated SO ₂ plumes near the source shortly before satellite overpasses. This high-resolution data enables more robust identification and precise characterization of strong SO ₂ emissions, surpassing the capabilities of lower-resolution OMPS measurements, which may overlook or underestimate vigorous degassing periods. Notably, this high-resolution data also facilitates the detection of pre-eruptive SO ₂ emissions. Cloud cover can obscure SO ₂ plumes from satellite observations, but our inverse modeling procedure effectively distinguishes and tracks them by assimilating successive satellite overpass data. Furthermore, this procedure proves less susceptible to ash emissions compared to geostationary Himawari-8/AHI observations. We apply our methodology to study the 2018 Ambrym eruption, a former major volcanic SO ₂ emitter. This eruption marked the end of long-lived lava lake activity and initiated a submarine eruption through a massive magma intrusion. Our detailed SO ₂ flux time series unveils the evolution of the eruption and identifies distinct SO ₂ sources, including lava flows and shallow magma intrusions. In summary, the assimilation of TROPOMI data into inverse modeling procedures offers significant potential for enhancing our understanding of magma transport and environmental impacts during volcanic eruptions.