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 (1º x 1º) 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
Based on our model experiments we conclude that a global 6º x 9º resolution is too coarse to
represent the polar vortex, whereas the higher resolutions, 3º x 2º and
1º x 1º, yield similar results, even with a 6º x 9º 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., 3, 1833-1847, doi:10.5194/acp-3-1833-2003, 2003.