• 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.

• 대기
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• 제24권2호
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• pp.189-196
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• 2014

The definition of onset date of Changma is revisited in this study using a quality controlled Ieodo ocean research station data. The Ieodo station has great importance in terms of its southwest location from Korean Peninsula and, hence, makes it possible to predict Changma period in advance with less impact of continents. The onset date of Changma using the Ieodo station data is defined by the time that meridional wind direction changes and maintains from northerly to southerly, and then the zonal wind changes from easterly to westerly after first June. This definition comes from a recognition that the establishment and movement of the western North Pacific subtropical high (WNPSH) cause Changma through southwesterly flow. The onset data of Changma has been determined by large-scale dynamic-thermodynamic characteristics or various meteorological station data. However, even the definition based on circulation data at the Ieodo station has a potential for the improved prediction skill of the onset date of Changma. The differences between before and after Changma, defined as Ieodo station data, are also found in synoptic chart. The convective instability and conspicuous circulations, corresponding low-level southwesterly flow related to WNPSH and strong upper-level zonal wind, are represented during Changma.

• 대한원격탐사학회지
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• 제36권4호
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• pp.557-571
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• 2020

High-resolution flows around a steep mountainous island (Ulleungdo) in Korea were simulated by a computational fluid dynamics (CFD) model. To cover entire Ulleungdo and to resolve the topography around the Ulleungdo automatic synoptic observing system (ASOS) with high resolution, one-way nested grid system with large (60 m), and small (20 m) grid sizes was applied in the CFD model simulations. We conducted the numerical simulations for 16 inflow directions, and, for each inflow direction, we considered six different wind velocities(5, 10, 15, 20, 25, and 30 m s^-1) at the reference height (1,000 m). The effects of topography on surface wind observations were well reflected in the observed wind roses for the period of January 01, 2012 ~ December 31, 2016 at the Ulleungdo ASOS and marine buoy. Wind roses at the Ulleungdo ASOS was reproduced based on the CFD simulations. The changes in surface winds at the Ulleungdo ASOS caused by surrounding topography were relatively well simulated by the CFD model. The simulated wind-rose indicated that south-southwesterly and northeasterly were the dominant wind directions, which were also observed at the Ulleungdo ASOS. We investigated the flow characteristics around the Ulleungdo ASOS for northwesterly, south-southwesterly, and northeasterly winds in detail.

• 대한원격탐사학회지
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• 제34권5호
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• pp.763-775
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• 2018

본 연구에서는 지리정보시스템(GIS)자료와 전산유체역학(CFD) 모델을 사용하여 방풍벽이 건물 밀집 지역에 위치한 공사 지역에서 발생하는 대기오염물질의 확산에 미치는 영향에 대해 분석하였다. 부산 ASOS에서 10년 동안 관측된 풍속을 평균하여 기준 고도(지상 10 m)에서의 유입류로 사용하였다. 수치 실험은 방풍벽 건설 전과 5 m 및 10 m 높이의 방풍벽을 건설한 후에 대해 16 방위 풍향을 유입류로 진행하였고, 부산 ASOS에서 높은 빈도를 나타낸 북동풍과 남남서풍에 대한 상세 흐름을 분석하였다. 북동풍에서는 북동쪽에서 불어오는 흐름에 의해 비산 먼지가 확산되어 공사 지역 내부에 위치한 감천초등학교에서 대기오염물질 농도가 높게 나타났다. 5 m 높이의 방풍벽을 설치했을 때는 방풍벽 설치 전에 비해 풍속이 조금 감소했고 비산 먼지의 확산이 줄었다. 10 m 높이의 방풍벽을 설치한 경우, 초등학교에서의 평균 대기오염물질 농도는 37% 감소하였다. 남남서풍 유입류에서는 지형과 건물의 영향으로 공사 지역에서 복잡한 흐름 패턴이 형성되었다. 남쪽 공사 지역에서는 비산 먼지가 정체되어 농도가 높게 나타난 반면, 초등학교는 북풍의 흐름에 의해 대기오염물질 농도가 높게 나타났다. 방풍벽 건설 후에는 공사 지역 내부에서 풍속이 감소하면서 공사장 내부 농도는 높아졌지만, 초등학교에서의 농도는 감소했다.

• 대기
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• 제22권1호
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• pp.97-107
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• 2012

To investigate variation of aerosol number concentration at each different size with three-dimensional (3D) wind components in ocean area, aerosol particles and 3D wind components were measured in the Ieodo Ocean Research Station, which is located to 419 km southwest from Marado, the southernmost island of Korea, from 25 June to 8 July 2010. The Laser Particle Counter (LPC) and ultrasonic anemometer were used to measure the size of aerosol particles and 3D wind components (zonal (u), meridional (v), and vertical (w) wind) respectively. Surface weather chart, NCEP/NCAR reanalysis data and sounding data were used to analyze the synoptic condition. The distribution of aerosol number concentration had a large variation from bigger particles more than 1.0 ${\mu}m$ in diameter by wind direction during precipitation. In the number concentration of aerosol particles with respect to the weather conditions, particles larger than 1.0 ${\mu}m$ in size were decreased and sustained to the similar concentration at smaller particles during precipitation. The increase in aerosol number concentration was due to the sea-salt particles which was suspended by southwesterly and upward winds. In addition, the aerosol number concentration with vertical wind flow could be related with the occurrence and increasing mechanism of aerosol in marine boundary layer.