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S. Chabrillat

Evaluation of different analyses with a single CTM: challenges and benefits

The formulation of the underlying AGCM is very important to determine the coupling strategy with the CTM. The BASCOE CTM was originally developed to be driven by analyses from ECMWF, i.e. computed by the spectral model IFS. The coupling in this case is optimal thanks to an algorithm developed at KNMI (Bregman et al., ACP, 2003) which derives mass-conserving fluxes from vorticity and divergence in spectral space. The BASCOE CTM has been adapted to also accept analyses from the Canadian meteorological Center, i.e. from the grid-based model GEM. We will use long-lived stratospheric tracers to show the different transport characteristics in each case, and discuss the challenges and benefits in using a single CTM to evaluate completely different analyses.

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