Interactive Stratospheric Aerosol models response to different amount and altitude of SO₂ injections during the 1991 Pinatubo eruption

Abstract

Abstract. Recent model inter-comparison studies highlighted model discrepancies in reproducing the climatic impacts of large explosive volcanic eruptions, calling into question the reliability of global aerosol model simulations for future scenarios. Here, we analyse the simulated evolution of the stratospheric aerosol plume following the well observed June 1991 Mt. Pinatubo eruption by six interactive stratospheric aerosol microphysics models in comparison to a range of observational data sets. Our primary focus is on the uncertainties regarding initial SO2 emission following the Pinatubo eruption in 1991, as prescribed in the Historical Eruptions SO2 Emission Assessment experiments (HErSEA), in the framework of the model intercomparison project ISA-MIP. Six global models with interactive aerosol microphysics took part in this study: ECHAM6-SALSA, EMAC, ECHAM5-HAM, SOCOL-AERv2, ULAQ-CCM and UM-UKCA. Model simulations are performed by varying SO2 injection amount (ranging between 5 and 10 Tg-S), and the altitude of injection (between 18–25 km). We find that the common and main weakness among all the models is that they can not reproduce the persistence of the sulfate aerosols in the stratosphere. Most models show a stronger transport towards the extratropics in the northern hemisphere, at the expense of the observed tropical confinement, suggesting a much weaker subtropical barrier in all the models, that results in a shorter e-folding time compared to the observations. Moreover, the simulations in which more than 5 Tg-S of SO2 are injected show a large surface area density a few months after the eruption compared to the values measured in the tropics and the in-situ measurements over Laramie. This results in an overestimation of the number of particles globally during the build-up phase, and an underestimation in the Southern Hemisphere, which draws attention to the importance of including processes as the ash injection and the eruption of Cerro Hudson.

Immediate and Long‐Lasting Impacts of the Mt. Pinatubo Eruption on Ocean Oxygen and Carbon Inventories

“…Newer data sets presented in Quaglia et al. (2022) suggest an approximately symmetric aerosol distribution is more consistent with observations. Such a symmetric aerosol forcing would likely drive a greater carbon and oxygen flux response in the Southern Ocean.…”

“…For these experiments, CESM-LE had zero aerosol forcing in the Southern Ocean from mid-1991 to mid-1992, and then a forcing that is roughly a 30% underestimated at the peak forcing in late 1992. Newer data sets presented in Quaglia et al (2022) suggest an approximately symmetric aerosol distribution is more consistent with observations. Such a symmetric aerosol forcing would likely drive a greater carbon and oxygen flux response in the Southern Ocean.…”

“…In-situ sampling (Bakker et al, 2016) in the Southern Ocean may have been too sparse to allow for accurate reconstructions (Gloege et al, 2021) by these products or other mechanisms may be responsible for the observed large amplitude Southern Ocean decadal variability in observation-based products (Gruber et al, 2019). One caveat to this finding comes from the aerosol forcing files used in CESM1 which appear to underestimate aerosol loading in the southern hemisphere (Mills et al, 2016;Neely III et al, 2016;Quaglia et al, 2022). Newer estimates for the aerosol forcing files would likely lead to substantially more cooling and ventilation enhancement in the Southern Ocean…”

Interactive stratospheric aerosol models' response to different amounts and altitudes of SO2 injection during the 1991 Pinatubo eruption

“…Data availability. Simulation data are available at https://doi.org/10.7298/MM1S-AE98 (Quaglia et al, 2022).…”

Emulating Inconsistencies in Stratospheric Aerosol Injection

“…These aerosols would reflect a small fraction of incoming sunlight, and could be used to offset some fraction of the warming from anthropogenic greenhouse gasses (GHGs). The lifetime of aerosols injected into the stratosphere is of order of one year (Visioni 2018, Quaglia 2023, so for consistent radiative cooling, consistent injection strategies would be needed.…”