Extensive spatiotemporal analyses of surface ozone and related meteorological variables in South Korea for the period 1999–2010

Abstract

Abstract. Spatiotemporal characteristics of surface ozone (O 3 ) variations over South Korea are investigated with consideration of meteorological factors and timescales based on the Kolmogorov-Zurbenko filter (KZ filter), using measurement data at 124 air quality monitoring sites and 72 weather stations for the 12 yr period of 1999-2010. In general, O 3 levels at coastal cities are high due to dynamic effects of the sea breeze while those at the inland and Seoul Metropolitan Area (SMA) cities are low due to the NO x titration by local precursor emissions. We examine the meteorological influences on O 3 using a combined analysis of the KZ filter and linear regressions between O 3 and meteorological variables. We decomposed O 3 time series at each site into short-term, seasonal, and long-term components by the KZ filter and regressed on meteorological variables. Impact of temperature on the O 3 levels is significantly high in the highly populated SMA and inland region, but low in the coastal region. In particular, the probability of high O 3 occurrence doubles with 4 • C of temperature increase in the SMA during high O 3 months (May-October). This implies that those regions will experience frequent high O 3 events in a future warming climate. In terms of short-term variation, the distribution of high O 3 probability classified by wind direction shows the effect of both local precursor emissions and long-range transport from China. In terms of long-term variation, the O 3 concentrations have increased by +0.26 ppbv yr −1 (parts per billion by volume) on nationwide average, but their trends show large spatial variability. Singular value decomposition analyses further reveal that the long-term temporal evolution of O 3 is similar to that of nitrogen dioxide, although the spatial distribution of their trends is different. This study will be helpful as a reference for diagnostics and evaluation of regional-and local-scale O 3 and climate simulations, and as a guide to appropriate O 3 control policy in South Korea.

Spatiotemporal variations of air pollutants (O<sub>3</sub>, NO<sub>2</sub>, SO<sub>2</sub>, CO, PM<sub>10</sub>, and VOCs) with land-use types

“…Higher concentrations of the CNSP pollutants appeared in large cities (e.g., the SMA) more often than in suburban/rural areas. However, the O 3 values were lower over the large cities than over either their outer or coastal regions due to its reaction with other air pollutants and meteorological conditions (Seo et al, 2014). According to their study, the O 3 values over the large cities were low because of the NO titration, even during the night without photochemical reactions by local anthropogenic precursor emissions, while they were high in the coastal areas because of the sea breeze effect.…”

“…Seo et al (2014) revealed that the longterm trends of the local precursor emissions in O 3 in South Korea could affect the O 3 trends locally, and in the country, significant enhancement of the background O 3 negatively affected the air quality. In order to understand the negative relationship in trend between O 3 and CNSP pollutants, particularly NO 2 , we have investigated the relationship (i.e., correlation and weekly cycle) among O 3 , NO 2 and VOCs with the land-use types further in Sects.…”

“…7a), it will be important to understand possible factors causing such trends. Seo et al (2014) reported an increase in the O 3 (+0.26 ppb yr −1 ) in 46 cities in South Korea from 1999 to 2010. Also, the O 3 increase (+0.48 ppb yr −1 ) from 1990 to 2010, which was more consistent with our results, generally occurred for all of the seasons and day/night at most of the surface monitoring sites .…”

“…However, S. reported that in the suburban SMA, the biogenic VOCs could be the most important source of high O 3 episodes. The temporal O 3 averages in the SMA and other inland areas were low as a result of an increase in O 3 titration by NO from enhanced NO x levels compared to those at the coastal areas, sometimes due to a land-sea breeze (Ghim and Chang, 2000;Oh et al, 2006;Seo et al, 2014). In other words, the titration can slow down the O 3 accumulation in the urban (or suburban) areas due to significant concentrations of NO (Chou et al, 2006).…”

“…The cycles of each of the pollutants are helpful in order to understand the emission sources, human activities, photochemical processes and meteorological factors that affect it (e.g., Flemming et al, 2005;Meng et al, 2009). Seo et al (2014) reported that the O 3 trend in South Korea from 1999 to 2010 was similar to that of NO 2 , and it increased by +0.26 ppbv yr −1 , possibly due to the local increase in anthropogenic precursor emissions and meteorological effects. Based on a model simulation, Jin et al (2012) showed that the Seoul Metropolitan Area (SMA) was VOC-limited for the O 3 control, while the local province outside the SMA had the condition between VOC-limited and NO x -limited.…”