• 한국대기환경학회지
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• 제15권6호
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• pp.747-755
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• 1999

Effects of precipitation and cloud cover on high ozone days are examined by investigating the precipitation and average cloud cover before the ozone peak time within a day. High ozone days above 100 ppb in the Greater Seoul Area(GSA) for the ozone season from May to September are chosen for the analyses in terms of the surface meteorological data during 1990~1997. The result shows that the effect of precipitation on the rise of ozone concentration is definitely negative so that ozone concentration could not rise above 100ppb immediately after precipitation. But, the effect of cloud cover is associated with the variations of other meteorological parameters. The number of high ozone days with "zero" cloud cover is rather less than that with cloud cover of 1 to 4 since temperature is usually lower in "zero" cloud cover days. Furthermore, ozone concentration can rise above 100ppb even with full cloud cover when the wind is weak and the temperature is high.temperature is high.

• 한국환경과학회지
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• 제10권6호
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• pp.437-444
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• 2001

The characteristic features of surface ozone concentration and the forecasting procedure of high ozone days have been studied. The ozone concentration was continuously measured during 3 years (1997~1999) at air quality monitoring stations in five major cities in Korea. The diurnal variation of surface ozone concentration on high ozone days is characterized by low ozone concentration at night. The ozone concentration Increases continuously after sunrise, In reach a peak at 1500~1600 LST. Thereafter it decreases steadily to a low concentration at sunset. The diurnal and annual maximum of the surface ozone concentration at Seoul were observed in May and June, respectively. The favorable synoptic condition for the high ozone day is divided into 4 different synoptic weather patterns: a high-pressure system from the Sea of Okhotsk, the Pacific subtropical high extending westward, a moving high-pressure system covering the Korean peninsula. and a synoptic system In front of a typhoon. Most of high ozone days occur under the high pressure system in Korea.

• 한국대기환경학회지
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• 제15권3호
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• pp.267-280
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• 1999

To investigate the characteristics of high-ozone occurrences in the Greater Seoul Area(GSA), three high-ozone episodes were selected, for which the ozone warning for concentration above 120 ppb might be issued. The selection was on the basis of morning wind directions and speeds, and daily maximum ozone concentrations measured between 1990 and 1997. The episodes chosen to meet selection criteria were seven days in July 1992, nine days in July 1994, and three days in August 1994, as respectively characterized by southwesterly, easterly, and calm winds in the morning. However, more than 80% of high-ozone days in the GSA were associated with calm winds and the concomitant accumulation of local emission in the morning, rather than being due to transport of ozone or its precursors. This is believed to be the primary reason why ozone concentrations in the GSA varied in a completely different manner even between adjacent monitoring stations. Several premises for initiating research studies for resolving these local variations of ozone concentrations in the GSA are also discussed.

• 한국대기환경학회지
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• 제13권1호
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• pp.41-49
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• 1997

Status of photochemical air pollution in the Greater Seoul Area (GSA) between 1990 and 1995 was assessed in terms of frequency distributions, number of days exceeding standards, average concentration and meteorological effects. In Seoul compared with other areas in Korea, daily maximum concentration was higher but average concentration was not so high due to lower daily minimum from April to October. The top 5th percentile was high especially in summer season. Average number of days exceeding 100 ppb at monitoring stations in GSA was highest in 1994, the hottest year, but it was only 4 days a year. Mean meteorological pattern of high ozone days could be summarized as low wind speeds, high temperatures, strong solar radiation, and low precipitation. Westerlies were more frequent on high ozone days and at Pangi station located in the eastside of GSA, both number of high ozone days and average concentration were high. Effect of precursor transport on the rise of ozone concentration was, however, not consistently important on the whole in GSA.

• 한국환경과학회지
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• 제9권4호
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• pp.295-302
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• 2000

This study was conducted to investigate the characteristics of surface ozone concentration and occurrence of high ozone concentration using hourly ozone, nitrogen dioxide and meteorological data for 1997~1998 in Pusan coastal area. Monthly mean ozone concentration was the highest at Dongsamdong in Spring(35.4ppb), at Kwangbokdong in Fall(25.1ppb) and the lowest Dongsamdong(22.2ppb) and Kwangbokdong(16.0ppb) in Winter. Relative standard deviation indicating clearness of observation site was 0.42 at Dongsamdong and 0.49 at Kwangbokdong that is similar to urban area. The diurnal variation of ozone concentration of Dongsamdong and Kwangbokdong showed maximum at 1500~1600LST and minimum 0700~0800LST that typical pattern of ozone concentration. In ozone episode period(Sept. 10~15, 1998), diurnal change of ozone concentration was very high, and ozone concentration was related to meteorological parameters such as temperature, relative humidity, wind speed, cloud amount and radiation on a horizontal surface. During the episode days peak ozone concentrations are much higher than the normal values, wind speeds are always lower, and solar radiation is high with the exception of the September episode.

• 한국환경과학회지
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• 제11권12호
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• pp.1253-1259
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• 2002

This study analyzes the surface ozone, NO and $NO_2$ concentration data from 1997 to 1999 in Daegu. It investigates effect on precursor during high-ozone episode days. The high-ozone episode is defined when a daily maximum ozone concentration is higher than 100 ppb(ambient air quality standard of Korea) in at least one station among six air quality monitoring stations. The frequency of episodes is 13 days(33 hours). The frequency is the highest in May and September, and the area with the highest frequency is Nowondong and Manchondong. The average value of daily maximum ozone concentration with high ozone episode is 81.6 ppb, and that of 8-hour average ozone concentration is 58.6 ppb. It means that ozone pollution is continuous and wide-ranging in Daegu. The daily variation of NO, $NO_2$ and $O_3$ in high-ozone episodes are inversely proportional one another. Nowondong an industrial area, is affected by pollutants that are emitted from the primary sources, while Manchondong a residential area, is affected by the advection of $O_3$ or by the primary pollutants like VOCs.

• 한국대기환경학회지
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• 제15권4호
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• pp.441-455
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• 1999

Meteorological characteristics of three high-ozone episodes in the Greater Seoul Area, selected on the basis of morning-average wind direction and speed for the 1990~1997 period, were investigated. Three high-ozone episodes thus selected were seven days of July 3~9, 1992, nine days of July 21~29, 1994, and three days of August 22~24, 1994. Along with surface meteorological data from the Seoul Weather Station, surface and 850-hPa wind fields over the Northest Asia around the Korean Peninsula were used for the analysis. In the July 1992 episode, westerly winds were most frequent as a result of the influence of a high-pressure system in the west behind the trough. In contrast, in the July 1994 episode, easterly winds were most frequent due to the effect of a typhoon moving north from the south of Japan. Despite different prevailing wind directions in the two episodes, the peak ozone concentration of each episode always occurred when a sea-land breeze developed in association with weak synoptic forcing. The August 1994 episode, selected as being representative of calm conditions, was another typical example in which peak ozone concentration rose to 322 ppb under the well-developed sea-land breeze. All three high-ozone episodes were terminated by precipitation, and subsequent rises in ozone concentrations were also suppressed by a series of precipitation afterwards. In particular, two heavy rainfalls were the main reason why the August 1994 episode, with the highest and second-highest ozone concentrations during the 1990~1997 period, lasted for only a few days.

• 한국환경과학회지
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• 제24권8호
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• pp.993-1001
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• 2015

Comparing to the other air pollutants like $SO_2$, CO, the number of exceedance of the ozone national ambient air quality standard(NAAQS) and the ozone warning increased recently in Busan. The purpose of this study is to find out the preliminary symptoms for high ozone days in Busan area. In order to find out the preliminary symptoms, the hourly ozone data at air quality monitoring stations and the hourly meterological parameters at Busan regional meteorological 2007 to 2013 were used for the analysis. Averaged daily max ozone concentration was the highest(0.055 ppm) at Noksan and Youngsuri in the ozone season from 2007 to 2013. The horizontal distributions of daily max. ozone including all stations in Busan at high ozone days(the day exceeding 0.1 ppm of ozone concentration at least one station) were classified from two to five clusters by hierarchial cluster analysis. The meteorological variables showing strong correlation with daily max. ozone were the daily mean dew point temperature, averaged total insolation, the daily mean relative humidity and the daily mean cloud amount. And the most frequent levels were $19-23^{\circ}C$ in dew point temperature, $21-24 MJ/m^2$ in total insolation on the day before, $2.6-3.0 MJ/m^2$ on the very day, 67-80% in relative humidity and 0-3 in cloud amount.

• 한국대기환경학회지
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• 제18권4호
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• pp.253-264
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• 2002

Surface ozone concentrations measured at 40 monitoring sites in three major cities (Seoul, Busan, and Daegu) of Korea during 1993~2000 were analyzed to understand the characteristics of temporal and spatial distributions. Trends were analyzed for annual mean, 95th percentiles of daily 8-hour maximum and days exceeding 8-h ozone standard of 60 ppb. Three indicators exhibited increasing trends (+0.75 ppb yr$^{-1}$ , +2.20 ppb yr$_{-1}$ , and +5.35 days yr$_{-1}$ on average) throughout the study period at all cities. Diurnal and seasonal variations were the largest in Seoul followed by Daegue and Busan, due to the high photochemical production and titration of ozone (Seoul), strong wind and constant supply of background ozone from the ocean (Busan). In the urban centers and industrial areas at all cities, scavenging of ozone by NO reduces the daily 8-hour maximum ozone by 10 ppb on average. High concentrations of ozone have frequently occurred in downwind eastern (Seoul and Daegu) or northern (Busan) sides of the territory. In particular, the coastal area of Busan had relatively high ozone level due to the local sea land breeze circulation. The results indicated that the temporal and spatial variations of ozone concentration were non -uniform and were closely related to the local environments; emission levels, climates, and geographic locations.

• 한국대기환경학회지
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• 제20권4호
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• pp.503-514
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• 2004

In Seoul metropolitan area, nocturnal variation of surface ozone concentrations observed at 27 monitoring sites from 1998 to 2002 showed that high ozone levels occurred frequently during the spring. Frequency distributions for nighttime ozone indicated that elevated concentrations in spring were influenced by advection of different air mass compared to other seasons. Surface wind analysis during the spring revealed that relatively strong southwesterly winds were associated with nocturnal ozone enhancement, which can be attributed to the regional transport of ozone. In order to identify the origin of nocturnal ozone enhancement in spring, 3-day backward trajectories were calculated by HYSPLIT 4 for the episode days and then classified. The results showed that NW, W, and SW flows, indicating influence of polluted air masses from the China continent, have 51% in a]1 the episode days, which suggest that the nocturnal ozone enhancement can occur under the effect of long-range transport of ozone-laden air mass on a regional scale. Case study of nocturnal ozone maxima associated with long-range transport was discussed in more detail in the light of meteorological conditions. Southwesterly synoptic flow along the outer edge of moving high-pressure system was found to be the important cause of nocturnal ozone maxima in Seoul. This flow could lead to be long-range transport of ozone that had effectively accumulated in the stagnating portion of the system located eastern coast of China. Low atmosphere soundings, backward trajectories, and elevated ozone and CO levels at the back-ground tiles gave evidence for regional effects on nocturnal ozone enhancement In Seoul.