Abstract. 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 , NO 2 , 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.

Heat waves and heavy rainfall are regarded as two of the most frequent and widespread severe weather hazards (UNDRR & CRED, 2020;WEF, 2020). Heat waves are characterized by a period of abnormally high temperatures lasting three or more days, and heavy rainfall is a primary cause of flooding. Different from concurrent heat waves and droughts, heat waves and heavy rainfall are usually considered as isolated events, given that the two contrasting weather extremes seldom co-occur in the same place (Mukherjee & Mishra, 2021;Ridder et al., 2020). Nonetheless, there may be a lagged connection between heat waves and heavy rainfall in consideration of the interaction and mutual dependence between temperature and precipitation (Y.

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Previousstudies have typically considered one hazard (humid heat or pluvial flooding) and its impacts at a time. In recent years, a number of studies have investigated the spatiotemporal compounding of multiple extremes, defined as "compound events" (

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