ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-6-1599-2006 On the ability of chemical transport models to simulate the vertical structure of the N<sub>2</sub>O, NO<sub>2</sub> and HNO<sub>3</sub> species in the mid-latitude stratosphere Berthet G. 1 2 Huret N. 2 Lefèvre F. 1 Moreau G. 2 Robert C. 2 Chartier M. 2 Catoire V. 2 Barret B. 3 Pisso I. 4 Pomathiod L. 2 Service d’Aéronomie, Institut Pierre-Simon Laplace, Paris, France Laboratoire de Physique et Chimie de l’Environnement, Orléans, France Laboratoire d’Aérologie, Observatoire de Midi-Pyrénées, Toulouse, France Laboratoire de Météorologie Dynamique, Institut Pierre-Simon Laplace, Paris, France 18 05 2006 6 6 1599 1609 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/6/1599/2006/acp-6-1599-2006.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/1599/2006/acp-6-1599-2006.pdf

In this paper we study the impact of the modelling of N<sub>2</sub>O on the simulation of NO<sub>2</sub> and HNO<sub>3</sub> by comparing in situ vertical profiles measured at mid-latitudes with the results of the Reprobus 3-D CTM (Three-dimensional Chemical Transport Model) computed with the kinetic parameters from the JPL recommendation in 2002. The analysis of the measured in situ profile of N<sub>2</sub>O shows particular features indicating different air mass origins. The measured N<sub>2</sub>O, NO<sub>2</sub> and HNO<sub>3</sub> profiles are not satisfyingly reproduced by the CTM when computed using the current 6-hourly ECMWF operational analysis. Improving the simulation of N<sub>2</sub>O transport allows us to calculate quantities of NO<sub>2</sub> and HNO<sub>3</sub> in reasonable agreement with observations. This is achieved using 3-hourly winds obtained from ECMWF forecasts. The best agreement is obtained by constraining a one-dimensional version of the model with the observed N<sub>2</sub>O. This study shows that the modelling of the NO<sub>y</sub> partitioning with better accuracy relies at least on a correct simulation of N<sub>2</sub>O and thus of total NO<sub>y</sub>.