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 ba nd-pass filtering analysis of the Total Ozone Mapping Spectrometer (TOMS) s atellite observations over a 20-year period. Low-ozone episodes, or minihol es, appear more frequent over the Euro-Atlantic sector in the high NAO phas e, when the prevailing, upper tropospheric westerly jet is displaced polewa rd and acquires a stronger northward tilt relative to climatology. Thus, th e tendency of the NAO to remain in its high phase in late eighties and nine ties accounts for recent observations of more frequent minihole conditions and episodes of low-latitude, ozone-poor intrusions into high-latitude regi on of this sector.