Observation of Polar Stratospheric Clouds down to the Mediterranean coast P. Keckhut1, Ch. David1, M. Marchand1, S. Bekki1, J. Jumelet1, A. Hauchecorne1, and M. Höpfner2 1Service d'Aéronomie, Institut Pierre Simon Laplace, B.P. 3, 91371, Verrières-le-Buisson, France 2Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung, Karlsruhe, Germany
Abstract. A Polar Stratospheric Cloud (PSC) was detected for the first time in January
2006 over Southern Europe after 25 years of systematic lidar observations.
This cloud was observed while the polar vortex was highly distorted during
the initial phase of a major stratospheric warming. Very cold stratospheric
temperatures (<190 K) centred over the Northern-Western Europe were
reported, extending down to the South of France where lidar observations
were performed. CTM (Chemical Transport Model) investigations show that this
event led to a significant direct ozone destruction (35 ppb/day), within and
outside the vortex as chlorine activated air masses were moved to sunlight
regions allowing ozone destruction. If such exceptional events of
mid-latitudes PSCs were to become frequent in the future, they should not
compromise the ozone recovery because their effect appears to be limited
temporally and spatially. More importantly, these events might tend to be
associated with the initial phase of a stratospheric warming that results
into a weakening and warming of the polar vortex and hence into a reduced
probability occurrence of PSC temperatures during the rest of the winter.
Citation: Keckhut, P., David, Ch., Marchand, M., Bekki, S., Jumelet, J., Hauchecorne, A., and Höpfner, M.: Observation of Polar Stratospheric Clouds down to the Mediterranean coast, Atmos. Chem. Phys., 7, 5275-5281, doi:10.5194/acp-7-5275-2007, 2007.