Independent and compound characteristics of PM_2.5, ozone, and extreme heat pollution events in Korea

In the context of global warming and rapid urbanization, the frequency of simultaneous occurrence of extreme high temperature, ozone pollution, and particulate matter pollution has increased. However, independent and composite characterization of PM_2.5, ozone, and extreme heat pollution events has not been systematically analyzed so far. This study combines meteorological and pollutant data with the GTWR model in an attempt to reveal the patterns of independent heat days (IHD), compound PM_2.5-ozone pollution (CPOP), and composite heat-PM_2.5-ozone pollution (CHPOP). In this study, we found that in July and August in South Korea, the frequency of CPOP events, the frequency of CHPOP events, and the composite proportion of CHPOP events all show an overall pattern of east-high and west-low; the atmospheric circulation patterns of the three extreme events have brought about more stagnation conditions, which may be related to cyclone activity; the occurrence of CPOP events is mainly accompanied by a continuous decrease in relative humidity and cloud cover, both IHD and CHPOP events occur with increasing temperatures, decreasing cloudiness, and anomalously high pressures; under the same events, excluding relative humidity, PM_2.5 and ozone showed similar conditions with respect to the dependence on temperature, wind speed, barometric pressure, cloudiness, and nitrogen dioxide. This study identified the independent and composite characteristics of PM_2.5, ozone, and extreme heat pollution events, which can enhance early prediction and pollution prevention of these extreme events.