The Asian summer monsoon (ASM) is the governing circulation pattern in the Northern Hemisphere during boreal summer. Studies investigating aerosol and tracer distributions show that the ASM effectively uplifts tropospheric air and pollutants, forms an apparently stable reservoir in the lowermost stratosphere, and releases air into the lower stratosphere via multiple pathways. This project will address two open key questions:

• How permeable is the transport barrier associated with the ASM?
• How does the ASM circulation control troposphere-stratosphere exchange?

These questions will be addressed by making use of comprehensive observations and Lagrangian transport analyses. The measurement data sets contributed by the partners comprise global satellite measurements, ground-based remote sensing and in-situ balloon measurements within the ASM anticyclone, and in-situ aircraft measurements outside the ASM anticyclone. In this project we will use two Lagrangian transport models, the global chemistry-transport model CLaMS and the Lagrangian particle dispersion model MPTRAC.

The main objectives of the project are

1. to compile observational data for transport studies regarding the ASM,
2. to create a new and comprehensive emission inventories for carbon monoxide and volcanic sulfur dioxide emissions, and
3. to analyze transport pathways in the troposphere and lower stratosphere connected with the ASM circulation.

Atmospheric scientist and computer scientists from the University of Mainz and the Jülich Supercomputing Centre in Germany and from the Institute of Atmospheric Physics of the Chinese Academy of Sciences and the University of Guangzhou in China will work together to address these objectives in the framework of this project proposed to the 2018 bilateral Joint Sino-German Research Projects call.