Aerosol-induced Dynamical perturbation of the stratosphere: The 2017 Pacific Northwest Pyrocumulonimbus Event

The Pacific Northwest pyrocumulonimbus Event (PNE) took place in British Columbia during the nighttime hours between the 12th and 13th of August 2017. Several pyroconvective clouds erupted in this occasion, and released in the upper troposphere/lower stratosphere unprecedented amounts of carbonaceous aerosols (300 ktn). The stratospheric aerosol plume persisted in the stratosphere for several months, while gradually rising up to 22 km and dispersing around the entire northern hemisphere. In this study, we use the Goddard Earth Observing System Atmospheric General Circulation Model (GEOS AGCM) to study the pertubations that the aerosol plume from the PNE event induced on the stratospheric meteorology. Our simulations include the radiative interactions of aerosols, so that their impacts on temperatures and winds are explicitly simulated . In this work, we show how the presence of the carbonaceous aerosols from the PNE event triggers the formation and maintenance of a synoptic scale stratospheric anticyclone. We follow this disturbance considering the potential vorticity anomaly and the brown carbon aerosol loading and we describe its dynamical structure and evolution in time. The analysis presented here shows that the simulated anticyclone undergoes daily expansion-compression cycles governed by the radiative heating, which are directly related to the vertical motion of the plume, and that the aerosol radiative heating is essential in maintaining the anticyclone itself.