1. Studies of Stratospheric NO y Chemistry with Three- Dimensional Chemical Transport Model Wuhu Feng 1, Martyn Chipperfield 1, Stewart Davies 1, B. Sen 2, G. Toon 2, J.F. Blavier 2, W. Kouker 3, G.P. Stiller 3, R. Ruhnke 3, TOPOZ and VINTERSOL Scientists 1. School of the Environment, University of Leeds, U.K 2. NASA Jet Propulsion Laboratory, Pasadena, CA, U.S.A. 3. IMK, Forschungzentrum Karlsruhe, Germany fengwh@env.leeds.ac.uk, martyn@env.leeds.ac.uk References Chipperfield, M.P., JGR, 104, 1781-1805, 1999. Feng W, et al, JAS, (in poress) Popp, P,J., et al., GRL, 28, 2875-2878, 2001. Acknowledgments We are grateful to all TOPOZ and VINTERSOL scientists. The work is supported by TOPOZ III project and U.K. NERC UTLS OZONE Programme.Meteorological analyses have been provided by the ECMWF via British Atmospheric Data Centre (BADC). 3. Antarctic sudden warming in 2002: Comparison with MIPAS Fig 4. Correlation of NO y v N 2 O on December 16, 2002 for Mk IV data (triangles) and SLIMCAT model (+). Also shown is calculated NO y * v N 2 O from a third-order polynomial [Popp, et al., 2001] using Mk IV and model N 2 O 2. SLIMCAT 3D CTM 3D off-line chemical transport model.  -  vertical coordinate Detailed chemical scheme (see Chipperfield [1999]). 4.1 2002/03 Arctic winter: Comparison with MK IV balloon 1. Introduction NO y (N, NO, NO 2, NO 3, HNO 3, ClONO 2, N 2 O 5, HNO 4,..) species play an important role in the chemistry of stratospheric O 3. Within the European Union TOPOZ III project we are comparing current CTM models with a range of NO y observations to test our understanding of NO y chemistry under different conditions. In this poster, the SLIMCAT model results are compared with MIPAS during the Antarctic sudden warming event in 2000. We also compared with measurements (MK IV balloon and geophysic M55 aircraft data) in 2002/03 Arctic winter during the SOLVE/VINTERSOL campaigns. Fig 5. Mk IV-Observed (solid lines) and SLIMCAT-modelled (dashed lines) profiles of NO y species on December 16, 2002 Fig 6. As Fig 5, but for ratios of the individual species with respect to total NO y. 4.2 2002/03 Arctic winter: Comparison with Geophysic M55 aircraft SLIMCAT captures denitrification and renitrification signal remarkably well and major features of the NO y species based on an ice sedimentation scheme Fig1. Comparison of N 2 O, O 3, NO y between SLIMCAT and MIPAS observations at 20Km on Sep. 18 and 26, 2002 Fig2. As Fig 1., but for HNO 3 and ClONO 2. Fig3. Profile comparison of NO y and its components for four select locations: right of top profile is outside the vortex on 26/09/2002 SLIMCAT successful produce the evolution of Antarctic polar vortex and vortex split in 2002, and also gives a good simulation of NO y and its components structure above 20Km. However, modelled N 2 O 5 is still poor. Fig 7. Comparison of modelled NO y, N 2 O and O 3 using different radiation schemes with in-situ observations on the selected three EUPLUX flights Fig 8. Comparison of modelled O 3 with sondes at Ny-Alesund station using CCM and MIDRAD radiation schemes. SLIMCAT gives good simulation of NO y for the cold region while the model overestimates denitrification at T>200K due to equilibrium scheme; Model with CCM radiation scheme gives better descent of airmasses and succesfful reproduce the 2002/03 Arctic polar O 3 loss