A high O-3 episode with the large increases in surface ozone by 21-42 ppbv and the nocturnal surface O-3 levels exceeding 70 ppbv was observed in the region between Xiamen and Quanzhou over the southeastern coast of China during 12-14 June 2014, before the Typhoon Hagibis landing. Variations in the surface O-3, NO2, CO and meteorology during the Typhoon Hagibis event clearly suggest a substantial impact of the peripheral downdrafts in the large-scale typhoon circulation on such an O-3 episode excluding the contributions of photochemical production and the horizontal transport. The influence of vertical O-3 transport from the upper troposphere and lower stratosphere (UTLS) region on high surface O-3 levels is further confirmed by a negative correlation between surface O-3 and CO concentrations as well as dry surface air observed during the O-3 episode. This study provides observational evidence of typhoon-driven intrusion of O-3 from the UTLS region to surface air, revealing a significant effect of such a process of stratosphere-troposphere exchange (STE) of O-3 on tropospheric O-3 and ambient air quality.
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