Size-dependent aerosol chemistry in the lower stratosphere

Airborne in-situ aerosol composition measurements show that the lower stratospheric aerosol is a combination of relatively pure sulfuric acid particles that originated in the stratosphere alongside mixed organic-sulfate particles that originated in the troposphere. New data from the Atmospheric Tomography (ATom) mission provide some of the first observations of aerosol composition in the Southern Hemisphere stratosphere.

The ATom data show that in the lowermost stratosphere in both hemispheres the pure sulfuric acid particles are larger than the mixed organic-sulfate particles. Stratospheric mixed particles with significant organic content are almost identical to those in the upper troposphere, confirming their tropospheric origin. In contrast, the sulfuric acid particles are completely distinct from tropospheric particles. Several of the stratospheric sampling periods were very different from the others, indicating the variability in the lowermost stratosphere. The 2015 Calbuco eruption was still affecting the Southern Hemisphere lower stratosphere in 2016. Biomass burning particles were observed in the Northern Hemisphere lowermost stratosphere in 2017 and a huge amount of dust was present in the Northern Hemisphere lowermost stratosphere in spring 2018.