Long-term trends of surface ozone in Korea

To gain a better understanding of the state of the art of surface ozone in Korea, the trends of several indicators were presented based on the extensive surface ozone monitoring data in 16 administrative districts and Baekryeong island, a background area. Important indicators such as the annual mean of hourly mean surface ozone (AVG1), the daily maximum 8-h values (MDA8), and the AVG1 during daytime (D-AVG1) were high in background areas while low in urban areas including the Seoul Metropolitan Area (SMA). It implies that regional background level largely determines the ozone characteristics in Korea while local photochemical reactions affect the ozone levels in individual district. This hypothesis was validated by the frequency of the high ozone episodes by district. Spatial and temporal heterogeneity of surface ozone in Korea were high, thus, there should be control policy district by district based on the target indicator(s).