Relationship of surface O3 to large-scale circulation patterns during two recent winters -: art. no. L06108

[1] We demonstrate a direct connection between large-scale circulation patterns and surface O-3 using atmospheric observations obtained during winters 2002 and 2003. Measurements at two rural sites in the northeastern U.S. revealed that median mixing ratios of O-3 in winter 2003 were increased by up to 80% compared to 2002, and greatly exceeded previous spring annual maximums. To explain this we propose that strong meridional flows in winter 2003 frequently transported O-3-rich mid-tropospheric air masses from high latitudes to the northeastern U.S. while cooling regional climate 4.4degreesC below normal. Our measurements also show that an exceptionally elevated spring O-3 maximum occurred in 2003. The impact from this winter enhancement on the levels of O-3 and other species during the following months will be largely driven by actual climatic conditions.