Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 1 2008 10.5194/acpd-8-137-2008 http://www.atmos-chem-phys-discuss.net/8/137/2008/ http://www.atmos-chem-phys-discuss.net/8/137/2008/acpd-8-137-2008.html http://www.atmos-chem-phys-discuss.net/8/137/2008/acpd-8-137-2008.pdf 137 160 2008-01-08 Sensitivity of tracer transport to model resolution, forcing data and tracer lifetime in the general circulation model ECHAM5 A. Aghedo S. Rast M. G. Schultz Max Planck Institute for Meteorology, Hamburg, Germany ICG-2, Research Centre, Jülich, Germany The transport of tracers in the general circulation model ECHAM5 is analysed using 9 independent idealized tracers with constant lifetimes released in different altitude regions of the atmosphere. The source regions were split into the tropics, Northern and Southern Hemisphere. The dependency of tracer transport on model resolution is tested in the resolutions T21L19, T42L19, T42L31, T63L31 and T106L31, by employing tracers with a globally uniform lifetime of 5 months. Each of the experiments uses prescribed sea surface temperatures and sea ice fields of the 1990s. The influence of meteorology and tracer lifetimes were tested by performing additional experiments in the T63L31 resolution, by nudging ECHAM5 towards the European Centre for Medium Range Weather Forecast 40 years re-analysis data (ERA40), and by using tracer lifetimes of 0.5 and 50 months, respectively. The transport of tracers is faster in the finer resolution models and is mostly dependent on the number of vertical levels. We found a decrease in the inter-hemispheric transport of tracers with source region at the surface or the tropopause in the coarse resolution models due to increasing recirculation within the source region and vertical mixing. 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