Atmospheric Chemistry and Physics Discussions
www.atmos-chem-phys-discuss.net
1680-7367
1680-7375
5
6
2005
10.5194/acpd-5-12465-2005
http://www.atmos-chem-phys-discuss.net/5/12465/2005/
http://www.atmos-chem-phys-discuss.net/5/12465/2005/acpd-5-12465-2005.html
http://www.atmos-chem-phys-discuss.net/5/12465/2005/acpd-5-12465-2005.pdf
12465
12503
2005-11-29
Stratosphere-troposphere exchange in a summertime extratropical low: analysis
J. Brioude
brij@aero.obs-mip.fr
J.-P. Cammas
O. R. Cooper
Laboratoire d’Aérologie, UMR5560, Observatoire Midi-Pyrénées, Toulouse, France
Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado/NOAA Aeronomy Laboratory, Boulder, USA
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 (O<sub>3</sub>≃100 ppbv;
CO≃90 ppbv) in the dry airstream of the cyclone,
and again in the upper troposphere (O<sub>3</sub>≃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 (O<sub>3</sub>≃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.