Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 5 2005 10.5194/acpd-5-9169-2005 http://www.atmos-chem-phys-discuss.net/5/9169/2005/ http://www.atmos-chem-phys-discuss.net/5/9169/2005/acpd-5-9169-2005.html http://www.atmos-chem-phys-discuss.net/5/9169/2005/acpd-5-9169-2005.pdf 9169 9205 2005-09-23 Modelling study of the impact of deep convection on the UTLS air composition – Part II: Ozone budget in the TTL avenue de la Recherche Scientifique, 45071 Orléans cedex 2, France E. D. Rivière V. Marécal N. Larsen S. Cautenet Laboratoire de Physique et Chimie de l’Environnement/CNRS and Université d’Orlèans, 3A Danish Meteorological Institute, Division of Middle Atmosphere Research, Lyngbyvej 100, DK-2100, Copenhagen, Denmark Laboratoire de Météorologie Physique/CNRS-OPGC/Université Blaise Pascal, 24 Avenue des Landais, 63177 Aubière cedex, France In this second part of a series of two papers which aim to study the local impact of deep convection on the chemical composition of the Upper Troposphere and Lower Stratosphere (UTLS), we focus on ozone simulation results using a mesoscale model that includes on-line chemistry. A severe convective system observed on 8 February 2001 at Bauru, Brazil, is studied. We show that there is an increase in the ozone concentration in the tropical transitional layer (TTL) in the model during this event, which is compatible with ozone sonde observations from Bauru during the 2004 convective season. The model horizontal variability of ozone in this layer is comparable with the variability of the ozone sonde observations in the same area. The calculation of the ozone budget in the TTL shows that the ozone behaviour in this layer is mainly driven by dynamics. The upward motions at the bottom of the TTL, related to the convection activity is the main contributor to the budget since it can explain 75% of the total ozone increase in the TTL, while the chemical ozone production inside the TTL is estimated to be 23.5% of the ozone increase if NO_x production by lightning (LNO_x) is taken into account. It is shown that downward motions at the tropopause induced by gravity waves generated by deep convection are non negligible in the TTL ozone budget, since it represents 11% of the ozone increase. The correlation between the convection activity and the vertical flux at 13 km, the vertical flux at 17 km, and the chemical production is brought to the fore in this simulation.