Atmos. Chem. Phys. Discuss., 5, 12465-12503, 2005
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Stratosphere-troposphere exchange in a summertime extratropical low: analysis
J. Brioude1, J.-P. Cammas1, and O. R. Cooper2
1Laboratoire d’Aérologie, UMR5560, Observatoire Midi-Pyrénées, Toulouse, France
2Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado/NOAA Aeronomy Laboratory, Boulder, USA

Abstract. Ozone and carbone monoxide measurements sampled during two commercial flights in airstreams of a summertime midlatitude cyclone are analysed with a lagrangian-based study (backward trajectories and a Reverse Domain Filling technique) to gain a comprehensive understanding of transport effects on trace gas distributions. The study demonstrates that summertime cyclones can be associated with deep stratosphere-troposphere transport. A tropopause fold is sampled twice in its life cycle, once in the lower troposphere (O3≃100 ppbv; CO≃90 ppbv) in the dry airstream of the cyclone, and again in the upper troposphere (O3≃200 ppbv; CO≃90 ppbv) on the northern side of the large scale potential vorticity feature associated with baroclinic development. In agreement to the maritime development of the cyclone, the chemical composition of the anticyclonic part outflow of the warm conveyor belt (O3≃40 ppbv; CO≃85 ppbv) corresponds to the lowest mixing ratios of both ozone and carbone monoxide in upper tropospheric airborne observations. The uncertain degree of confidence of the Lagrangian-based technique applied to a 100 km segment of upper level airborne observations with high ozone (200 ppbv) and relatively low CO (80 ppbv) observed northwest of the cyclone prevents to identify the ozone enrichment process of air parcels embedded in the cyclonic part of the upper level outflow of the warm conveyor belt. Different hypotheses of stratosphere-troposphere exchange are discussed.

Citation: Brioude, J., Cammas, J.-P., and Cooper, O. R.: Stratosphere-troposphere exchange in a summertime extratropical low: analysis, Atmos. Chem. Phys. Discuss., 5, 12465-12503, doi:10.5194/acpd-5-12465-2005, 2005.
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