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Conclusion:

DIAL Lidar observations and the radiosounding observations on stratospheric ozone obtained at Reunion island offer the opportunity to analyse a case study of quasi-horizontal stratospheric transport, between 550K and 700K, around the 12^th July 2000. This transport has been diagnosed from the dynamic barrier detection LOBADY code and the high resolution PV advection MIMOSA code. It appears that the air masses that interest Reunion island from the 12^th of July, and that induce a high PV increase, come from midlatitudes. This isentropic way up is consecutive to the formation of an air filament coming from equatorial latitudes, characterised by low PV, stretched to the south east and isentropically mixed in the midlatitudes surf zone. This transport from midlatitudes are perfectly according with the anomalies observed on Reunion island ozone profiles on the 12^th of July.

The installation of a stratospheric DIAL lidar at Reunion Island, and the implementation of performant diagnostic tools for dynamic analysis, enable today to think of making more complete studies on stratospheric transport in this tropical region. Such studies should document the transport through the subtropical stratospheric barrier and the long term ozone evolution.

Acknowledgement : I would like to thank all the LPA radiosoundings team, the technical and scientific LIDAR team from Service d'Aéronomie of CNRS. I would like to thank particularly Jean-Luc Baray for helpful comments and suggestions. HALOE data are issued from NASA Langley Research Centre.