A high O3 episode with the large increases in surface ozone by21–42 ppbv and the nocturnal surface O3 levels exceeding 70 ppbv wasobserved in the region between Xiamen and Quanzhou over the southeasterncoast of China during 12–14 June 2014, before the Typhoon Hagibis landing.Variations in the surface O3, NO2, CO and meteorology during theTyphoon Hagibis event clearly suggest a substantial impact of the peripheraldowndrafts in the large-scale typhoon circulation on such an O3 episodeexcluding the contributions of photochemical production and the horizontaltransport. The influence of vertical O3 transport from the uppertroposphere and lower stratosphere (UTLS) region on high surface O3levels is further confirmed by a negative correlation between surface O3and CO concentrations as well as dry surface air observed during the O3episode. This study provides observational evidence of typhoon-drivenintrusion of O3 from the UTLS region to surface air, revealing asignificant effect of such a process of stratosphere–troposphere exchange(STE) of O3 on tropospheric O3 and ambient air quality.
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