Ozone Flux Measurements and Data Correction in Coastal Megacities in South Korea Busan and Ulsan, South Korea

Since the mid-1990s, ozone concentrations in the United States and Europe have steadily declined, whereas South Korea has experienced an increase to this day. Identifying the scientific causes of the ozone increase is essential, which necessitates an accurate understanding of the ozone budget equation. To quantify the ozone budget equation, it also requires measurements of dry deposition velocity. However, the dry deposition velocity is highly uncertain due to surface conditions and turbulence. Eddy covariance (EC) methods are used to measure ozone dry deposition velocities. However, the ozone flux studies using the EC method in Korea have not been conducted to our knowledge. In this study, ozone flux was directly measured using the EC method over approximately one month in the coastal megacities, Busan and Ulsan, in Korea, and here, we present the preliminary results of ozone fluxes and dry deposition velocities in the urban surface of coastal cities.

The preprocessing steps included despike, double rotation, time lag calculation, ozone concentration correction, and detrending. Diurnal variations in ozone concentrations showed a unimodal distribution in Ulsan, a typical pattern for photochemical products, whereas a bimodal distribution was observed in Busan due to a combination of local production and transport from upwind regions. The average daytime ozone flux was -3.1 nmol·m^-2·s^-1 in Busan and -1.3 nmol·m^-2·s^-1 in Ulsan. A more detailed discussion, including comparisons with previous studies, will be presented. 

 

Acknowledgments

This work was funded by the Korea Meteorological Administration Research and Development Program under Grant RS-2024-00404042.