• Journal of the Korean earth science society
• /
• v.25 no.6
• /
• pp.474-483
• /
• 2004

This paper analyzed the characteristics of daily ozone variations over Kangreung and Wonju. It was found that the diurnal cycle of ozone over Wonju has a primary ozone peak in the afternoon and a minimum around sunrise, which is a typical diurnal ozone cycle observable in the urban area. However, the cycle over Kangreung shows a primary peak in the afternoon and secondary peak around 3 a.m. The amounts of ozone in the secondary peak is occasionally higher than that in the primary peak. This nocturnal ozone peak is frequently observed year-round, and the highest frequency and extent are observed in spring. The possible cause of this nocturnal ozone increase was investigated using meteorological parameters and the HYSPLIT trajectory model. It was found that the nocturnal ozone peak is highly correlated with strong wind speed, which has led to positive temperature anomaly. The trajectory model revealed that when the secondary peak occurred, the air was originated from the west and a sinking motion subsequently followed. These findings suggested that when the westerly wind is strongest in spring, the polluted airs from urban areas are transported to the upper boundary layer over Kangreung area. In the case of strong wind during the night, nocturnal ozone peaks were produced by active vertical mixing between lower boundary and upper boundary layers.

• Journal of Korean Society for Atmospheric Environment
• /
• v.32 no.4
• /
• pp.372-383
• /
• 2016

This study aimed at analyzing the sensitivity of ozone simulation in accordance with the meteorological nudging for a high nocturnal ozone episode. To demonstrate the effectiveness of nudging methods (e.g., nudging techniques and application domains), the following six experiments were designed: (1) control without nudging, (2) experiment with application of observation nudging to all domains (domain 1~4), and (3)~(6) experiments with application of grid nudging to domain 1, domain 1~2, domain 1~3 and all domains, respectively. As a result, the meteorological nudging had a direct (improvement of input data) and indirect (estimate natural emission) effect on ozone simulation. Nudging effects during the daytime were greater than those during the nighttime due to low accuracy of wind direction during the nighttime. On comparison of the nudging techniques, the experiments in which grid nudging was applied showed more improved results than the experiments in which observation nudging was applied. At this time point, the simulated concentrations were generally similar to the observed concentrations due to the increase in the nudging effect when grid nudging was applied up to the sub-domain. However, for high nocturnal ozone uptakes, the experiment in which grid nudging was applied do domain 1~3 showed better results than the other experiments. This is because, when grid nudging was applied to the high resolution domain (e.g., domain 4 with 1 km), the local characteristics were removed due to the smoothing effects of meteorological conditions.

• Journal of Korean Society for Atmospheric Environment
• /
• v.25 no.4
• /
• pp.289-303
• /
• 2009

The chemical and meteorological effects on the concentration variations of ozone ($O_3$) were evaluated based on the intensive air quality measurement (5 pollutants and aromatic volatile organic compounds (AVOCs)) in and out-side an urban valley during spring and summer of 2006. The 5 pollutants measured in the study area include $O_3$, $NO_2$, NO, $PM_{10}$, and CO; the AVOCs include benzene (BEN), toluene (TOL), ethylbenzene (EB), m,p-xylene (MPX), and o-xylene (OX). For the purpose of this study, study areas were classified into two categories: valley area (VA) with a semi-closed topography covering a number of industrial complex, public building, and mountains and non-valley area (NVA) surrounding the suburban and residential areas. In general, the mean concentration levels of most pollutants (except for $PM_{10}$) in the VA were higher than those in the NVA. It was found that the average $O_3$ increase in the VA during spring might result from the combined effects such as the photochemical production from diverse anthropogenic sources and the $O_3$ accumulation due to geographical features (e.g., the semi-closed topography) and wind conditions (e.g., a low wind speed). In addition, the nocturnal $O_3$ increase in the VA during spring was primarily caused by local wind conditions (e.g., mountain and valley winds) with the low wind speed (approximately $1{\sim}2\;m\;s^{-1}$). On the other hand, the $O_3$ difference between the two areas during summer might be because of the photo-chemical production with the $O_3$ precursors (especially the AVOCs) rather than the contribution of wind conditions.

• Journal of Environmental Science International
• /
• v.26 no.5
• /
• pp.621-638
• /
• 2017

Meteorological characteristics related to variations in ozone ($O_3$) concentrations in the Korean peninsula before, during, and after Typhoon Talas (1112) were analyzed using both observation data and numerical modeling. This case study takes into account a high $O_3$ episode (e.g., a daily maximum of ${\geq}90ppb$) without rainfall. Before the typhoon period, high $O_3$ concentrations in the study areas (e.g., Daejeon, Daegu, and Busan) resulted from the combined effects of stable atmospheric conditions with high temperature under a migratory anticyclone (including subsiding air), and wind convergence due to a change in direction caused by the typhoon. The $O_3$ concentrations during the typhoon period decreased around the study area due to very weak photochemical activity under increased cloud cover and active vertical dispersion under a low pressure system. However, the maximum $O_3$ concentrations during this period were somewhat high (similar to those in the normal period extraneous to the typhoon), possibly because of the relatively slow photochemical loss of $O_3$ by a $H_2O+O(^1D)$ reaction resulting from the low air temperature and low relative humidity. The lowest $O_3$ concentrations during the typhoon period were relatively high compared to the period before and after the typhoon, mainly due to the transport effect resulting from the strong nocturnal winds caused by the typhoon. In addition, the $O_3$ increase observed at night in Daegu and Busan was primarily caused by local wind conditions (e.g., mountain winds) and atmospheric stagnation in the wind convergence zone around inland mountains and valleys.

• Journal of Korean Society for Atmospheric Environment
• /
• v.24 no.2
• /
• pp.196-205
• /
• 2008

Variability in vertical ozone and meteorological profiles was measured by 2Z electrochemical concentration cells (ECC) ozonesonde at Bangyi in Seoul ($37.52^{\circ}N$, $127.13^{\circ}E$) during June $6{\sim}9$, 2003 in odor to identify the vertical distribution of ozone and its relationship with the lower-atmospheric structure resulted in the high ozone concentrations near the surface. The eight profiles obtained in the early morning and the late afternoon during the study period clearly showed that the substantial change of ozone concentrations in lower atmosphere(${\sim}5\;km$), indicating that it is tightly coupled to the variation of the planetary boundary layer (PBL) structure as well as the background synoptic flow. All profiles observed early in the morning showed very low ozone concentrations near the surface with strong vertical gradients in the nocturnal stable boundary layer due to the photochemical ozone loss caused by surface NO titration under very weak vertical mixing. On the other hand, relatively uniform ozone profiles in the developed mixing layer and the ozone peaks in the upper PBL, were observed in the late afternoon. It was noted that a significant increase in ozone concentrations in the lower atmosphere occurred with the corresponding decrease of the mixing height in the late afternoon on June 8. Ozone in upper layer did not vertically vary much compared to that in PBL but changed significantly on June 6 that was closely associated with the variation of synoptic flows. Interestingly, heavily polluted ozone layers aloft (a maximum value of 115 ppb around 2 km) were formed early in the morning on 6 through 7 June under dominant westerly synoptic flows. This indicates the effects of the transport of pollutants on regional scale and consequently can give a rise to increase the surface ozone concentration by downward mixing processes enhanced in the afternoon.