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Ann. Geophys., 20, 547-557, 2002
www.ann-geophys.net/20/547/2002/
© European Geosciences Union 2002
Ozone generation over the Indian Ocean during the South African biomass-burning period: case study of October 1992.
F. G. Taupin1,2, M. Beekmann3, P. J. Brémaud1, and T. Randriambelo1
1Laboratoire de physique de l’atmosphère, Université de la R´eunion, 97715 Saint-Denis messag cedex 9, France
2Now at LPCE-CNRS, 45071 Orléans cedex 2, France
3Service d’Aéronomie du CNRS, Université Pierre et Marie Curie, Paris, 75252 Paris Cedex 05, France
Correspondence to: F. G. Taupin (goffinon@cnrs-orleans.fr)
Abstract. In this study, we present
an estimation of photochemical ozone production during free tropospheric
transport between the African biomass burning area and Reunion Island (Indian
Ocean) by means of trajectory-chemistry model calculations. Indeed, enhanced
ozone concentrations (80–100 ppbv) between 5 and 8 km height over Reunion
Island are encountered during September–October when African biomass burning
is active. The measurements performed during flight 10 of the TRACE-A campaign
(October 6, 1992) have been used to initialise the lagrangian
trajectory-chemistry model and several chemical forward trajectories, which
reach the area of Reunion Island some days later, are calculated. We show that
the ozone burden already present in the middle and upper troposphere over
Southern Africa, formed from biomass burning emissions, is further enhanced by
photochemical production over the Indian Ocean at the rate of 2.5 - 3 ppbv/day.
The paper presents sensitivity studies of how these photochemical ozone
production rates depend on initial conditions. The rates are also compared to
those obtained by other studies over the Atlantic Ocean. The importance of our
results for the regional ozone budget over the Indian Ocean is briefly
discussed.
Key words. Atmospheric composition
and structure (evolution of the atmosphere; troposphere – composition and
chemistry); meterorology and atmospheric dynamics (tropical meteorology)
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