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5. Summary and future plans

Globally integrated flux of ozone has been shown to depend on heterogeneous chemistry on stratospheric aerosol. The model calculates 686 Tg(Ozone)/year when heterogeneous chemistry on stratospheric aerosol and PSCs is included. Without heterogeneous chemistry in the stratosphere this value increases to 757 Tg(Ozone)/year.

Ozone and NOy are significantly increased in the UTLS region due to air traffic. The downward flux of NOy through the tropopause is very sensitive to emissions of aircraft occurring in the stratosphere.

Preparations are now going on for use of meteorological data from a 40-layer forecast model extending from the surface, by which the vertical resolution in the lower stratosphere will be improved by a factor of two. Furthermore, upper boundary conditions are going to be based on observations rather than data from the Oslo 2D model. Alternatively the model domain could be extended up to 0.1 hPa by use of the ECMWF 60 layer model.

Regarding chemistry the following possibilities we consider the inclusion of:

• Cl and Br chemistry in the upper troposphere
• hydrocarbon chemistry in the lower stratosphere

·        a microphysical scheme for a more detailed description of particle formation and distribution

·        particle sedimentation from the lower stratosphere into the troposphere (dehydrification/denitrification)

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