Asian Summer Monsoon Pollutes the Northern Hemispheric Stratosphere

An enhanced aerosol layer near the tropopause over Asia during the period of the Asian summer monsoon (ASM) was recently identified by satellites. Previous modeling studies suggest the layer is largely composed of organics and sulfate. However its source, detailed distribution, and climate implications are presently not well understood. To address this issue, in-situ measurements of aerosol size distribution during the 2015 ASM were made from Kunming, China. These showed a robust aerosol enhancement up to 2 km above the tropopause. We use a global climate model coupled with the Community Aerosol and Radiation Model for Atmospheres (CARMA) to show that these aerosol particles are transported to the entire 10°N - 50°N latitude band in the lower stratosphere. These transported particles, originally formed in the region of the ASM anticyclone, account for a significant fraction of total aerosol mass in the 10°N - 50°N latitude band between 16 to 20 km.