Impact of the latitude of stratospheric aerosol injection on the
Southern Annular Mode
Abstract
The impacts of Stratospheric Aerosol Injection strategies on the
Southern Annular Mode (SAM) are analysed with the Community Earth System
Model (CESM). Using a set of simulations with fixed single-point SO2
injections we demonstrate the first-order dependence of the SAM response
on the latitude of injection, with the northern hemispheric and
equatorial injections driving a response corresponding to a positive
phase of SAM and the southern hemispheric injections driving a negative
phase of SAM. We further demonstrate that the results can to first order
explain the differences in the SAM responses diagnosed from the two
recent large ensembles of geoengineering simulations utilising more
complex injection strategies - GLENS and ARISE-SAI - as driven by the
differences in the simulated sulfate aerosol distributions. Our results
point to the meridional extent of aerosol-induced lower stratospheric
heating as an important driver of the sensitivity of the SAM response to
the injection location.