An observed and analysed stratospheric ozone intrusion over the high Canadian Arctic UTLS region during the summer of 2003

An exceptional ozone increase in the upper troposphere-lower stratosphere region has been recorded by an ozone sounding performed over the high Canadian Arctic at the beginning of August 2003. Simultaneously observed low humidity and low tropopause height suggest that this anomalous ozone enhancement is attributed to a downward transport from the stratosphere. This latter transport is investigated by using the Ertel potential vorticity field calculated from the ECMWF analyses. The occurrence of such high ozone concentrations is shown to be due to stratospheric ozone-rich air intrusions. These latter mesoscale phenomena are successfully captured using the assimilation of Envisat/MIPAS ozone profiles into the global three-dimensional chemistry transport model of Météo-France (MOCAGE). This study shows that Envisat/MIPAS ozone profiles assimilation adds value in the sense that the analyses capture the whole stratospheric intrusion episode, whereas the raw model simulation does not.