The 2021 Stratospheric Aerosol Layer: Comparison of Model Results and Observations

Stratospheric aerosols are important due to their scattering of shortwave radiation and absorption of longwave radiation generally leading to surface cooling and stratospheric heating. They also provide a surface for heterogeneous reactions to occur, which can result in stratospheric ozone depletion. It is therefore important to understand the various influences on the formation of stratospheric aerosols. The Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) aircraft campaign revealed an enhanced aerosol layer in the lower stratosphere over the central U.S. during July and August 2021 that was not observed during the 2022 deployment or in 2020 balloon-borne measurements. The cause of the aerosol layer remains undetermined. A hypothesis is that the volcanic eruption of Soufrière St. Vincent on April 9th, 2021, contributed to the observed enhancement. This study aims to model the Soufrière eruption using the global chemistry-climate and aerosol microphysical model SOCOL-AERv2 nudged to the observed wind and temperature fields. This study will examine the processes that control the model's response to volcanic perturbation. Preliminary results suggest that the eruption's magnitude may be too small to meaningfully impact the stratospheric aerosol layer; however, significant disagreements between observations and model results complicate the interpretation of this finding. Disagreements will be discussed.