[Influence of Typhoon Nangka Process on Ozone Pollution in Hainan Island]

In order to explore the influence of the 2016 typhoon Nangka on ozone (O₃) concentration in Hainan Island, this study employed correlation analysis and backward trajectory simulated methods, using the hourly air quality monitoring data, meteorological data, EAR5 reanalysis data, and bright temperature (TBB) infrared from the Himawari-8 satellite from October 10 to 14, 2020. The results showed that, during the typhoon process from October 11 to 13, the O₃-8h (maximum of 8 hours sliding average) concentration exceeded the standard. The averaged ρ(O₃-8h) of Hainan Island reached its peak value (130.5 μg·m^-3) in October 12, 2020, with the O₃-8h concentration exceeding the standard in four cities and counties, in which Lingao County reached the highest concentration of 198.44 μg·m^-3. During the typhoon process, the hourly O₃ concentration was negatively correlated with precipitation, relative humidity, and wind speed and positively correlated with air pressure and air temperature. Moreover, the correlation coefficients between O₃ with precipitation, air pressure, and relative humidity exceeded the 99.9% confidence level. The southeastern coastal provinces of China were the main contribution source area for this ozone pollution process on Hainan Island. Affected by the downdraft inside the western Pacific subtropical high (WPSH) and the downdraft outside the circumference of typhoon Nangka, vertical transport in the atmosphere appeared over the contribution source area. The meteorological conditions were favorable for atmospheric photochemical reactions. Air pollutants were transported to Hainan Island along the northeast airflow around the typhoon, resulting in the occurrence of an O₃ pollution event. In addition, this study built a weather conceptual model of O₃ pollution in Hainan Island affected by typhoon Nangka, which can be used as a reference for the joint pollution prevention and control by air pollution prediction, early warning, and environmental management departments.