Chemical effects in 11-year solar cycle simulations with the Freie Universitaet Berlin Climate Middle Atmosphere Model with online chemistry (FUB-CMAM-CHEM)

The impact of 11-year solar cycle variations on stratospheric ozone (O3) is studied with the Freie Universitaet Berlin Climate Middle Atmosphere Model with interactive chemistry (FUB-CMAM-CHEM). To consider the effect of variations in charged particle precipitation we included an idealized NO x source in the upper mesosphere representing relativistic electron precipitation (REP). Our results suggest that the NO x source by particles and its transport from the mesosphere to the stratosphere in the polar vortex are important for the solar signal in stratospheric O3. We find a positive dipole O3 signal in the annual mean, peaking at 40-45 km at high latitudes and a negative O3 signal in the tropical lower stratosphere. This is similar to observations, but enhanced due to the idealized NO x source and at a lower altitude compared to the observed minimum. Our results imply that this negative O3 signal arises partly via chemical effects.