Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 6 2004 10.5194/acpd-4-8285-2004 http://www.atmos-chem-phys-discuss.net/4/8285/2004/ http://www.atmos-chem-phys-discuss.net/4/8285/2004/acpd-4-8285-2004.html http://www.atmos-chem-phys-discuss.net/4/8285/2004/acpd-4-8285-2004.pdf 8285 8325 2004-12-15 Variability of the Lagrangian turbulent diffusivity in the lower stratosphere B. Legras legras@lmd.ens.fr I. Pisso G. Berthet F. Lefèvre Laboratoire de Météorologie Dynamique, UMR8539, Paris, France Service d’Aéronomie, UMR7620, Paris, France Ozone and nitrous oxide are measured at high spatial and temporal resolution by instruments flying on the ER-2 NASA research aircraft. Comparing the airborne transects to reconstructions by ensemble of diffusive backward trajectories allows to estimate the average vertical Lagrangian turbulent diffusion experienced by the air parcels. The resulting estimates show large Lagrangian diffusion of the order of 0.1 m² s^−1 outside the polar vortex in the surf zone and smaller values of the order of 0.01 m² s^−1 inside. Locally, large variation of Lagrangian diffusion occur over mesoscale distances. It is found that high temporal resolution (3 h or less) is required for off-line transport calculations and that the reconstructions are sensitive to spurious motion in standard analysed winds.