Atmos. Chem. Phys. Discuss., 3, 2261-2284, 2003
www.atmos-chem-phys-discuss.net/3/2261/2003/
doi:10.5194/acpd-3-2261-2003
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The impact of model grid zooming on tracer transport in the 1999/2000 Arctic polar vortex
M. M. P. van den Broek1, M. K. van Aalst2, A. Bregman3, M. Krol2, J. Lelieveld4, G. C. Toon5, S. Garcelon6, G. M. Hansford6, R. L. Jones6, and T. D. Gardiner7
1Space Research Organization of the Netherlands (SRON), Utrecht, The Netherlands
2Institute for Marine and Atmospheric Research (IMAU), Utrecht, The Netherlands
3Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
4Max-Planck-Institut für Chemie (MPI), Mainz, Germany
5Jet Propulsion Laboratory (JPL), Pasadena, USA
6Cambridge University, Cambridge, UK
7National Physical Laboratory (NPL), Teddington, UK

Abstract. We have used a 3D chemistry transport model to evaluate the transport of HF and CH4 in the stratosphere during the Arctic winter of 1999/2000. Several model experiments were carried out with the use of a zoom algorithm to investigate the effect of different horizontal resolutions. Balloon-borne and satellite-borne observations of HF and CH4 were used to test the model. In addition, air mass descent rates within the polar vortex were calculated and compared to observations.

Outside the vortex the model results agree well with the observations, but inside the vortex the model underestimates the observed vertical gradient in HF and CH4, even when the highest available resolution (1°×1°) is applied. The calculated diabatic descent rates agree with observations above potential temperature levels of 450 K. These model results suggest that too strong mixing through the vortex edge could be a plausible cause for the model discrepancies, associated with the calculated mass fluxes, although other reasons are also discussed.

Based on our model experiments we conclude that a global 6°×9° resolution is too coarse to represent the polar vortex, whereas the higher resolutions, 3°×2° and 1°×1°, yield similar results, even with a 6°×9° resolution in the tropical region.


Citation: van den Broek, M. M. P., van Aalst, M. K., Bregman, A., Krol, M., Lelieveld, J., Toon, G. C., Garcelon, S., Hansford, G. M., Jones, R. L., and Gardiner, T. D.: The impact of model grid zooming on tracer transport in the 1999/2000 Arctic polar vortex, Atmos. Chem. Phys. Discuss., 3, 2261-2284, doi:10.5194/acpd-3-2261-2003, 2003.
 
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