Untangling the Different Compositional and Dynamical Impacts of the 1991 Volcanic Eruptions of Cerro Hudson and Pinatubo

Cerro Hudson in southern Chile (45°S) erupted an estimated 4 Tg of sulfur dioxide over the period August 9-15, 1991, just two months after the cataclysmic eruption of Mount Pinatubo in the Philippines (18 Tg SO₂, 15°N, June 12-15). While Pinatubo's sulfur was the main component of stratospheric aerosol in the several years after 1991, we find that the majority of aerosol mass in the Southern Hemisphere extratropical stratosphere in the second half of 1991 originated from the Cerro Hudson eruptions. Here we have performed simulations of the months following the Pinatubo and Cerro Hudson eruptions with the Goddard Earth Observing System (GEOS) which includes the radiatively coupled Community Aerosol and Radiation Model for Atmospheres (CARMA) sectional aerosol module and a detailed stratospheric chemistry package. Using balloon-borne, satellite, and ground-based observations, we have constrained the relative impact of Cerro Hudson's 1991 eruptions on stratospheric dynamics and composition versus the contributions from Pinatubo. We have specifically focused on the impact on South Polar ozone in late 1991. Using the coupled model, we have resolved the heterogeneous chemical and radiative perturbations caused by these eruptions and compared them to the sparse observations from the period. This work has relevance to more recent and future Southern Hemisphere eruptions while also contributing to our understanding of the relatively better studied Pinatubo's impacts.