Regional Mountain Conference

The stratosphere-troposphere exchange couples the troposphere and the stratosphere and affects the chemical composition in the upper-troposphere/lower stratosphere region, which is important for the global radiative budget. This study combines high-resolution Weather Research and Forecasting model simulations of the Alpine region validated by observations during selected intensive observational periods of TEAMx and the Lagrangian particle dispersion model FLEXPART-WRF to investigate the transport of boundary layer emissions during the events of pronounced dynamical interaction between the orography and the flow. The Alpine orography was found to enhance transport and modify pathways through which emissions can penetrate the tropopause and the stratosphere region. This results from a non-trivial combination of convective updrafts, orographic lifting and mixing due to breaking orographic gravity waves near the surface and in the vicinity of the tropopause. Our study has important implications for climate model development in terms of parameterizing subgrid-scale orography effects and for our understanding of the transport of pollution in mountain regions and globally.