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In this second part of a series of two papers which aim to study the localimpact of deep convection on the chemical composition of the UpperTroposphere and Lower Stratosphere (UTLS), we focus on ozone simulationresults using a mesoscale model that includes on-line chemistry. A severeconvective system observed on 8 February 2001 at Bauru, Brazil, is studied.This unorganised convective system is composed of several convective cellsthat interact with each other. We show that there is an increase in the ozoneconcentration in the tropical transitional layer (TTL) in the model duringthis event, which is compatible with ozone sonde observations from Bauruduring the 2004 convective season. The model horizontal variability of ozonein this layer is comparable with the variability of the ozone sondeobservations in the same area. The calculation of the ozone budget in the TTLduring a 24 h period in the area of the convective system shows that theozone behaviour in this layer is mainly driven by dynamics. The horizontalflux at a specific time is the main contribution in the budget, since itdrives the sign and the magnitude of the total ozone flux. However, whenaveraged over the 24 h period, the horizontal flux is smaller than thevertical fluxes, and leads to a net decrease of ozone molecule number of23%. The upward motions at the bottom of the TTL, related to theconvection activity is the main contributor to the budget over the 24hperiod since it can explain 70% of the total ozone increase in the TTL,while the chemical ozone production inside the TTL is estimated to be 29%of the ozone increase, if NO<sub>x</sub> production by lightning (LNO<sub>x</sub>) istaken into account. It is shown that downward motion at the tropopauseinduced by gravity waves generated by deep convection is non negligible inthe TTL ozone budget, since it represents 24% of the ozone increase. Theflux analysis shows the importance of the vertical contributions during thelife time of the convective event (about 8 h). The TTL ozone is drivenout of the domain horizontally by the convective outflow during this period,limiting the ozone increase in this layer

Modelling study of the impact of deep convection on the UTLS air composition – Part 2: Ozone budget in the TTL