• 한국대기환경학회지
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• 제12권2호
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• pp.167-177
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• 1996

To investigate the source-receptor relationships aerosol model has been used to simulate the distribution behavior of the yellow sand. Data for meteorological fields were obtained by Meso-scale Analysis and Prediction Model System/Seoul National University (MAPMS/SNU) for five days (10-14 April 1988). To obtain the distributions of concentration of yellow sand,the aerosol model has been modified to allow quantifications of relative concentration distributions of yellow sand. Source regions of yellow sand were delineated by soil maps of China and emission rate as a function of wind stress(Westphal et al., 1987). Using 3-dimensional wind fields the backward trajectories from 3 receptor grids at the layer of .sigma. =0.95, 0.9, 0.85, 0.8 were calculated. In order to facilitate quantitative assessment of source-receptor relationships, it was assumed that the perturbations in along-trajectory and cross-trajectory proceed linearly with time, in accord with Gaussian distribution characteristics. On the basis of this assumption, the probability fields were calculated from every grid point with source strength 1. Using these probability fields and emission retes, the potential contributions of upstream sources along the trajectories were estimated. The results of this study indicate that the application of trajectory modeling is useful in investigating the quantitative relationship between source and receptor regions.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제1권1호
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• pp.19-33
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• 1997

The high oxidants, which occur the daily maximum concentrations in the afternoon, are transported into the other region via long range transport mechanisms or trapped within the shallow mixing boundary layer and then removed physically (deposition, transport by mountain wind, etc.) and chemically (reaction with local sources). Therefore, modeling formation of photochemical oxidants requires a complex description of both chemical and meteorological processes. In this study, as a part of air quality studies, we reviewed various aspects of photochemical modeling on the basis of currently available literature. The result of the review shows that the model is based on a set of coupled continuity equations describing advection, diffusion, transport, deposition, chemistry, emission. Also photochemical oxidant models require a large amount of input data concerned with all aspects of the ozone life cycle. First, emission inventories of hydrocarbon and nitrogen oxides, with appropriate spatial and temporal resolution. Second, chemical and photochemical data allowing the quantitative description of the formation of ozone and other photochemically-generated secondary pollutants. Third, dry deposition mechanisms particularly for ozone, PAN and hydrogen peroxide to account for their removal by absorption on the ground, crops, natural vegetation, man-made and water surfaces. Finally, meteorological data describing the transport of primary pollutants away from their sources and of secondary pollutants towards the sensitive receptors where environmental damage may occur. In order to improve our present study, shortcomings and limitation of existing models are pointed out and verification process through observation is emphasized.

• 한국대기환경학회지
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• 제14권3호
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• pp.191-208
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• 1998

Estimations of dry and wet depositions in Korea and the size distributions of yellow sand above Korea have been carried out using the Eulerian aerosol model with the simulated meteorological data from the SNU mesoscale meteorological model. The estimated particle size distribution in Korea shows a bimodal distribution with peak values at 0.6 pm and 7 pm and a minimum at 2 pm in the lower layer However, as higher up, the bimodal distribution becomes an unimodal distribution with a peak value at 4∼5mm. Among the total amount of yellow sand deflated in the source regions , the dry and wet deposition fluxes were about 92%, and about 1.3∼0.5%, repectively, and the rest(5∼6%) is suspended in the air, Most of dust lifted in the air during the clear weather is deposited in the vicinity of the source regions by dry deposition and the rest undergoes the long -range transport with a gradual removal by the wet deposition processes. Over Korean peninsula, the total amount of yellow sand suspended in the air was about 6∼8% of the emissions in the source region and the dry and wet deposition fluxes were about 0.005∼0.7% and 0.003∼0.051% of the total emitted amount, repectively. It is estimated that 2.7∼8.9 mesa-tons of yellow sand is transported annually over the Korean peninsula with the annual mean dry deposition of 2.1∼490 kilo-tons and the annual mean wet deposition of 1.5∼65 kilo-tons.

• 한국환경과학회지
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• 제26권2호
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• pp.183-200
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• 2017

The classification of airflow patterns during high ozone ($O_3$) and $PM_{10}$ episodes on Jeju Island in recent years (2009-2015), as well as their correlation with meteorological conditions according to classified airflow patterns were investigated in this study. The airflow patterns for $O_3$ and $PM_{10}$ were classified into four types (Types A-D) and three types (Types E-G), respectively, using the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and synoptic weather charts. Type A was the most dominant airflow pattern for $O_3$ episodes, being characterized by the transport of airflows from urban and industrial areas in China with the highest frequency (about 69%, with a mean of 67 ppb). With regard to the $PM_{10}$ episodes, Type E was the most dominant airflow pattern, and was mostly associated with long distance transport from Asian dust source regions along northwesterly winds, having the highest frequency (about 92%, with a mean of $136{\mu}g/m^3$). The variations in the concentration of $O_3$ and $PM_{10}$ during the study period were clarified in correlation with two pollutant and meteorological variables; for example, the high (low) $O_3$ and $PM_{10}$ concentrations with high (low) air temperature and/or wind speed and vice versa for precipitation. The contribution of long-range transport to the observed $PM_{10}$ levels in urban sites for different airflow patterns (Types E-F), if estimated in comparison to the data from the Gosan background site, was found to account for approximately 87-93% (on average) of its input. The overall results of the present study suggest that the variations in $O_3$ and $PM_{10}$ concentrations on Jeju Island are mainly influenced by the transport effect, as well as the contribution of local emissions.

• 한국응용과학기술학회지
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• 제15권4호
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• pp.11-20
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• 1998

The propagation of light radiation in a turbid medium is an important problem that confronts dosimetry of therapeutic laser delivery and the development of diagnostic spectroscopy. Scattered light is measured as a function of the position(distance r, depth z) between the axis of the incident beam and the detection spot. Turbid sample yields a very forward-directed scattering pattern at short range of position from source to detector, whereas the thicker samples greatly attenuated the on-axis intensity at long range of position. The portions of scattered light reflected from or transmitted throughphantom depend upon internal reflectance and absorption properties of the phantom. Monte Carlo simulation method for modelling light transport in tissue is applied. It uses the photon is moved a distance where it may be scattered, absorbed, propagated, internally reflected, or transmitted out of tissue. The photon is repeatedly moved until it either escape from or is absorbed by the phantom. In order to obtain an optimum therapeutic ratio in phantom material, optimum control the light energy fluence rate is essential. This study is to discuss the physical mechanisms determining the actual light dose in phantom. Permitting a qualitative understanding of the measurements. It may also aid in designing the best model for laser medicine and application of medical engineering.

• 한국지구과학회지
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• 제43권2호
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• pp.283-302
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• 2022

2020년 1월 23일 이후 중국에서 신종 코로나바이러스 감염증(COVID-19)으로 인한 봉쇄 조치가 전국으로 확대되고 있었다. 그러나, 한국에서는 2020년 2월 1-2일에 PM₁₀ 질량농도 일평균 최대 88-98 ㎍ m^-3의 고농도 연무가 발생하였다. 이 기간에 동아시아 지역은 850 hPa 기온 아노말리가 양(+), 동서류 아노말리는 음(-)으로 온난하고 정체적인 기단의 영향을 받고 있었다. 동아시아 지역의 인위적 배출량 감소에 따른 한국의 PM₁₀ 장거리 수송의 영향을 분석하기 위하여 WRF-Chem을 활용하였다. WRF-Chem에 인위적 배출량을 변화 없이 적용한 BASE와 인위적 배출량을 50%로 감소시켜 적용한 CTL의 PM₁₀을 한국의 지상 측정값과 민감도 분석을 수행하였다. CTL에서 PM₁₀의 IOA는 0.71로 BASE의 0.67보다 높게 나타났다. 이것은 중국의 COVID-19 봉쇄 조치로 인해 인위적 배출량이 감소한 것으로 분석된다. 또한, 한국 이외의 지역 배출량을 0으로 설정한 BASE_ZEOK와 CTL_ZEOK를 모의하여 BASE와 CTL에서의 장거리 수송 기여도의 변동을 분석하였다. CTL은 BASE와 비교하여 배출량이 50%로 감소하였지만 PM₁₀ 장거리 수송 기여도는 10-20% 감소한 것으로 나타났다. 동아시아 지역의 배출량 감소에 따라 풍하측 한국의 PM₁₀ 장거리 수송 기여도 변동이 선형적으로 반응하지 않는 것은 종관 기상 변동이 영향을 주는 것으로 보인다. 2월 1-2일 한국의 고농도 PM₁₀ 연무 사례에 대한 CTL에서 PM₁₀ 에어로졸 성분의 장거리 수송 기여도는 기타 무기물이 80-90%로 가장 높았고, 질산염은 30-60%, 황산염은 0-20%, 암모늄은 30-60%를 나타내고 있었다. 중국의 봉쇄 조치로 인하여 교통 및 물류 수송이 감소하면서 2차 에어로졸이 감소한 것으로 보인다.

• Wind and Structures
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• 제17권3호
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• pp.317-343
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• 2013

When evaluating flutter instability, it is often assumed that incident wind is normal to the longitudinal axis of a bridge and the flutter critical wind speed estimated from this direction is most unfavorable. However, the results obtained in this study via oblique sectional model tests of four typical types of bridge decks show that the lowest flutter critical wind speeds often occur in the yaw wind cases. The four types of bridge decks tested include a flat single-box deck, a flat ${\Pi}$-shaped thin-wall deck, a flat twin side-girder deck, and a truss-stiffened deck with and without a narrow central gap. The yaw wind effect could reduce the critical wind speed by about 6%, 2%, 8%, 7%, respectively, for the above four types of decks within a wind inclination angle range between $-3^{\circ}$ and $3^{\circ}$, and the yaw wind angles corresponding to the minimal critical wind speeds are between $4^{\circ}$ and $15^{\circ}$. It was also found that the flutter critical wind speed varies in an undulate manner with the increase of yaw angle, and the variation pattern is largely dependent on both deck shape and wind inclination angle. Therefore, the cosine rule based on the mean wind decomposition is generally inapplicable to the estimation of flutter critical wind speed of long-span bridges under skew winds. The unfavorable effect of yaw wind on the flutter instability of long-span bridges should be taken into consideration seriously in the future practice, especially for supper-long span bridges in strong wind regions.

• 대기
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• 제28권2호
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• pp.175-185
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• 2018

Characteristics of precipitation response to enhanced aerosols have been investigated during the severe haze events observed in Korea for 2011 to 2016. All 6-years haze events are classified into long-range transported haze (LH: 31%), urban haze (UH: 28%), and yellow sand (YS: 18%) in order. Long-range transported one is mainly discussed in this study. Interestingly, both LH (68%) and YS (87%) appear to be more frequently accompanied with precipitation than UH (48%). We also found out the different timing of precipitation for LH and YS, respectively. The variations of precipitation frequency for the LH event tend to coincide with aerosol variations specifically in terms of temporal covariation, which is in contrast with YS. Increased aerosol loadings following precipitation for the YS event seems to be primarily controlled by large scale synoptic forcing. Meanwhile, aerosols for the LH event may be closely associated with precipitation longevity through changes in cloud microphysics such that enhanced aerosols can increase smaller cloud droplets and further extend light precipitation at weaker rate. Notably, precipitation persisted longer than operational weather forecast not considering detailed aerosol-cloud interactions, but the timescale was limited within a day. This result demonstrates active interactions between aerosols and meteorology such as probable modifications of cloud microphysics and precipitation, synoptic-induced dust transport, and precipitation-scavenging in Korea. Understanding of aerosol potential effect on precipitation will contribute to improving the performance of numerical weather model especially in terms of precipitation timing and location.

• 한국환경보건학회지
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• 제35권1호
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• pp.21-35
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• 2009

The Asian dust storms which originated in the deserts of Mongolia and China transported particles to Korea and led to a high concentration of atmospheric particulate matters (PM) of more than $1000{\mu}g/m^3$ throughout the country in the spring, of 2007. Public concern, in Korea, about the possible adverse effects of these dust events has increased, as these dust storms can contain various air pollutants emitted from heavily industrialized eastern China. The objectives of this study were to understand the concentration characteristics of PM as a function of particle size between the Asian dust storm episodes and non-Asian dust period and to consider the mass size distribution of PM in the Asian dust storms and their water soluble ion species on the potential, possible effects on deposition levels in the three regions (nasopharyngeal, tracheobronchial, and alveolar) of the human respiratory system. The size distribution of PM mass concentration during the Asian dust storms showed a peak in the coarse particle region due to the long-range transport of soil particles from the deserts of Mongolia and China, which was identified by HYSPLIT-4 model for backward trajectory analysis of air arriving in the sampling site of Iksan. During the non-Asian dust period, there were two different types in PM size distribution: bimodal distribution when low concentrations of $PM_{2.5}$ were observed, while unimodal distribution having a peak in fine particle region when high concentrations of $PM_{2.5}$ were showed. This unimodal distribution with high concentrations of fine particulate and secondary air pollutants such as ${SO_4}^{2-}$, ${NO_3}^-$, ${NH_4}^+$ was found to be due to the long-range transport of air pollutants from industrialized eastern China. During the Asian dust storms, the mean concentrations of PM that can be deposited in the nasopharyngeal, tracheobronchial, and alveolar region were $128.8{\mu}g/m^3$, $216.5{\mu}g/m^3$, and $89.6{\mu}g/m^3$, respectively. During the non-Asian dust period, the mean concentrations of PM that can be deposited in the nasopharyngeal, tracheobronchial, and alveolar region were $8.4{\mu}g/m^3$, $9.5{\mu}g/m^3$ and $38.5{\mu}g/m^3$, respectively.

• 대한원격탐사학회지
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• 제30권2호
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• pp.241-249
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• 2014

본 연구에서는 광주과학기술원의 다파장 라만 라이다 시스템을 이용하여 2009년부터 2011년, 3년동안 광주에서 대기 에어로졸의 관측을 실시하였다. 관측된 라이다 신호의 분석으로부터 산출된 편광소멸도를 이용하여 황사의 층을 구분해 내었다. 구분 된 황사의 층의 고도에 따른 정보들은 Hybrid Single Particle Lagrangian Integrated Trajectory(HYSPLIT) 모델을 이용한 황사 층의 역궤적 분석에 이용되었고, 그 정보들을 통하여, 황사 층의 발원지 및 유입경로를 규명할 수 있었다. 한반도로 유입되는 황사는 고비사막을 기원으로 하는 경우가 가장 많은 것으로 나타났으며, 또한, 황사의 이동경로에 따른 광학적 특성 변화를 규명하기 위해, 중국 공업지역을 통과하여 유입된 황사 층과 발원지로부터 한반도로 직접적으로 유입된 황사의 구분하여 경로에 따른 입자 편광소멸도의 통계 분석을 실시하였다. 중국 공업지역을 통과하여 한반도로 유입된 황사의 편광소멸도는 0.07-0.1의 값을 보인 반면, 발원지로부터 공업지역을 경유하지 않고 직접 유입된 황사의 편광소멸도는 0.11-0.15로 상대적으로 높은 값을 보였다. 이는 발원지에서 발생한 순수 황사입자가 이동 중에 공업지역에서 발생한 오염입자와 혼합하여 황사층의 편광소멸도를 감소시킨 것으로 사료된다.