Cyclone induced East-Asian SO2 transport to the lower stratosphere: First proof by airborne measurements of SO2 and Fukushima Xe-133

The stratospheric aerosol layer contributes to the planetary albedo and influences stratospheric chemistry, and therefore is of considerable interest. The layer is thought to be formed preferably via SO2 injection by volcanic eruptions. Here, we report on observations of anthropogenic SO2 injection into the lower stratosphere. We have conducted airborne measurements of elevated SO2 and Fukushima Xe-133 at altitudes up to 13 km. The Xe-133, which was released by the March 2011 Fukushima nuclear power plant complex accident, is chemically inert and served as an ideal transport tracer. It has a half-live (against radioactive decay) of 5.25 days, similar to the SO2 half-live (against OH-induced conversion to aerosol particles). Our measurements unambiguously proved that cyclone induced injection of East-Asian SO2 containing planetary boundary layer air into the upper troposphere and lower stratosphere is operative. Implications of the observed injected stratospheric SO2 are discussed, including the formation and effects of stratospheric aerosol particles.