The North Atlantic Oscillation and the occurrences of ozone miniholes

The North Atlantic Oscillation (NAO) induces a clear signature on synoptic-scale ozone fluctuations over the Euro-Atlantic sector, as revealed by a band-pass filtering analysis of the Total Ozone Mapping Spectrometer (TOMS) satellite observations over a 20-year period. Low-ozone episodes, or miniholes, appear more frequent over the Euro-Atlantic sector in the high NAO phase, when the prevailing, upper tropospheric westerly jet is displaced poleward and acquires a stronger northward tilt relative to climatology. Thus, the tendency of the NAO to remain in its high phase in late eighties and nineties accounts for recent observations of more frequent minihole conditions and episodes of low-latitude, ozone-poor intrusions into high-latitude region of this sector.