In a new ACPD article, M. Rex and co-authors show the existence of a minimum in OH and tropospheric ozone column over the west Pacific, one of the main source regions for stratospheric air. This minimum amplifies the impact of surface emissions on the stratospheric composition, in particular emissions from biogenic halogenated species may have an impact on stratospheric ozone depletion, while increasing anthropogenic emissions of SO₂ from south east Asia and minor volcanic eruptions may affect the stratospheric aerosol budget. The full abstract can be found here.