• 한국환경과학회지
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• 제6권4호
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• pp.351-357
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• 1997

In the Atmosphere under the various physical and chemical condition different chemical reactions occur and there are a number of air pollutants which are generated by photochemical reaction by absorbing solar energy. Therefor various testing simulation was done as foundation work to develop the numerical model for the prediction of concentration of air pollutants. It was shown change of msjor air pollutants concentration In according to variation of photodissociation speed constant, Kl and Initial condition of air pollutants concentration which plays major role In photochemical reaction. The photochemical reaction model which was used In this study Is found to be useful for understanding relationship among the concentration of reacting air pollutants and the prediction of concentration of air pollutants in urban atmosphere.

• 환경영향평가
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• 제13권4호
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• pp.197-211
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• 2004

Visibility impairment was known as an indicator of the increased air pollution. In many previous studies, it is known that both directly emitted fine particles mainly from vehicles and secondary aerosols from photochemical reactions could contribute to this visibility impairment in addition to the meteorological condition. Furthermore, the visibility showed different change patterns according to the geographical condition. In order to research into the influence of these factors on visibility, this study analyzed the visibility at 15:00, observed from 1990 to 2001 in Seoul, Ganghwa, Susan, Gwangju, Jeju. As a result, the visibility was increased in Seoul except the rainfall period, but in Susan, Gwangju, Jeju, it decreased with the relative humidity (RH). Especially, in Seoul, the number of low visibility days was larger than other sites and variations of the visibility were sensitive to the concentration of air pollutants, such as TSP, $NO_2$, $O_3$. The visibility impairment was mainly observed in meteorological condition of RH<50% and relatively stationary front. Therefore it is inferred that photochemical smog could lead to the low visibility in Seoul. On the other hands, in Ganghwa and Susan, when RH was 60~70%, the low visibility observed under the influence of the transports of air pollutants from nearby cities as well as humid air mass from coastal region. And in Jeju, sea fog and humid air mass caused the visibility impairment when the RH was larger than 80%. Finally, during the observational period, some cases of low visibility phenomena were simultaneously observed in the vast region including Seoul, Susan, Ganghwa. It not only includes the visibility aggravation by Asian Dust, but also could be caused by the movement and diffusion of flying dust or secondary aerosols. Moreover, the result shows that these phenomena could be mainly influenced by meteorological factors covering the wide regions.

• 한국환경과학회지
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• 제27권1호
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• pp.11-25
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• 2018

Both the propagation velocity and the direction of atmospheric waves are important factors for analyzing and forecasting meteo-tsunami. In this study, a total of 14 events of meteo-tsunami over 11 years (2006-2016) are selected through analyzing sea-level data observed from tidal stations along the west coast of the Korean peninsula. The propagation velocity and direction are calculated by tracing the atmospheric disturbance of each meteo-tsunami event predicted by the WRF model. Then, the Froude number is calculated using the propagation velocity of atmospheric waves and oceanic long waves from bathymetry data. To derive the critical condition for the occurrence of meteo-tsunami, supervised learning using a logistic regression algorithm is conducted. It is concluded that the threshold distance of meteo-tsunami occurrence, from a propagation direction, can be calculated by the amplitude of air-pressure tendency and the resonance factor, which are found using the Froude number. According to the critical condition, the distance increases logarithmically with the ratio of the amplitude of air-pressure tendency and the square of the resonance factor, and meteo-tsunami do not occur when the ratio is less than 5.11 hPa/10 min.

• 대기
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• 제23권1호
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• pp.13-21
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• 2013

In this study, the effects of atmospheric stability and surface temperature on the microscale local airflow are investigated in a hydrological suburban area using a computational fluid dynamics (CFD) model. The model domain includes the river and industrial complex for analyzing the effect of water system and topography on local airflow. The surface boundary condition is constructed using a geographic information system (GIS) data in order to more accurately build topography and buildings. In the control experiment, it is shown that the topography and buildings mainly determine the microscale airflow (wind speed and wind direction). The sensitivity experiments of atmospheric stability (neutral, stable, and unstable conditions) represent the slight changes in wind speed with the increase in vertical temperature gradient. The differential heating of ground and water surfaces influences on the local meteorological factors such as air temperature, heat flow, and airflow. These results consequentially suggest that the meteorological impact assessment is accompanied by the changes of background land and atmospheric conditions. It is also demonstrated that the numerical experiments with very high spatial resolution can be useful for understanding microscale local meteorology.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.47-50
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• 2003

$CO_2$ concentration profile was measured to investigate whether $CO_2$ concentration at one level (i.e., eddy covariance measurement level) can be used to estimate storage term without significant uncertainty at broadleaf deciduous forest at Kwangneung experiment forest in Korea. Based on t-test with significance level of 5％, there was no statistical difference between storage term from one-level $CO_2$ concentration and one from $CO_2$ profile measurement. Storage term constitutes on average 5％ of half hourly net ecosystem exchange (NEE) even at unstable stability (i.e., well mixed condition), indicating that storage term should be considered even at daytime, which is sometimes neglected.

• 한국대기환경학회지
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• 제20권5호
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• pp.671-683
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• 2004

This study was carried out to understand long-range transport of $SO_2$ using aircraft measurements for the identification of it's horizontal and vertical concentration and distribution pattern. Thirteen missions of aircraft measurements have been done around 37$^{\circ}$00'/124$^{\circ}$30' from October 1997 to November 2001. Concentrations of $SO_2$ was 1.5~2.0 ppb in the below mixing layer, 0.6~1.1 ppb in the above mixing layer. $SO_2$ was found to be relatively higher than marine background level, 0.08~0.2ppb, indicating the western coast being influenced by long-range transport except for the summer season. The vertical distribution of $SO_2$ was classified into 3 groups using its vertical sounding and meteorology pattern; the first is linear decay pattern, the second is exponential decay pattern, and the last is gaussian distribution pattern in the below mixing layer, 2 patterns of linear decay and gaussian distribution patterns in the upper layer. It is founded that vertical distribution pattern is strongly dependent on meteorological condition, for example atmospheric stability and predominant air flow.

• 환경영향평가
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• 제22권6호
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• pp.609-626
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• 2013

Air quality models have been widely used to study and simulate many air quality issues. In the simulation, it is important to raise the accuracy of meteorological predicted data because the results of air quality modeling is deeply connected with meteorological fields. Therefore in this study, we analyzed the effects of meteorological fields on the air quality simulation. This study was designed to evaluate MM5 predictions by using different initial condition data and different observations utilized in the data assimilation. Among meteorological scenarios according to these input data, the results of meteorological simulation using National Centers for Environmental Prediction (Final) Operational Global Analysis data were in closer agreement with the observations and resulted in better prediction on ozone concentration. And in Seoul, observations from Regional Meteorological Office for data assimilations of MM5 were suitable to predict ozone concentration. In other areas, data assimilation using both observations from Regional Meteorological Office and Automatical Weather System provided valid method to simulate the trends of meteorological fields and ozone concentrations. However, it is necessary to vertify the accuracy of AWS data in advance because slightly overestimated wind speed used in the data assimilation with AWS data could result in underestimation of high ozone concentrations.

• 한국환경과학회지
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• 제5권4호
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• pp.411-427
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• 1996

A Lagrangian dispersion model has been developed to study the transport of atmospheric pollutants over the southern Korean peninsula on sunny summer days. A mesoscale atmospheric model has been employed to provide the wind fields and information for turbulent diffusion for the calculation of trajectories using a conditioned particle technique. The model has been applied to the simulation of the transport of atmospheric pollutants emitted from five sources in the coastal locations under various synoptic scale winds. Under calm synoptic scale condition, the particles emitted during daytime are mixed vertically and transported toward inland by sea-breeze, according to the model simulation. The particles are then transported upward at she sea-breeze front or by the upward motion over the mountain, and some particles show tendency of returning toward the coast by the return flow of the sea-breeze circulation. The particles are found to remain over the peninsula throughout the integration period under calm synoptic scale condition. When there is westerly synoptic scale winds the particles emitted in the west coast can reach the east coast within a day of faster depending on the speed. With a synoptic scale southerly wind of 5 m/s, most of the particles from the fine sources are advected toward inland during daytime. During nighttime, significant portion of particles released in the west coast remains over the land, while most particles released in the east coast move toward the sea to the east of the middle peninsula.

• 대기
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• 제25권2호
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• pp.261-270
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• 2015

Characteristics of snowfall and snow crystal habits have been investigated in the campaign of Experiment on Snow Storms At Yeongdong (ESSAY) using radiosonde soundings, Global Navigation Satellite System (GNSS), and a digital camera with a magnifier for taking a photograph of snowfall crystals. The analysis period is 6 to 14 February 2014, when the accumulated snowfall amount is 192.8 cm with the longest snowfall duration of 9 days. The synoptic situations are similar to those of the previous studies such as the Low pressure system passing by the far South of the Korean peninsula along with the Siberian High extending to northern Japan, which eventually results in the northeasterly or easterly flows and the long-lasting snowfall episodes in the Yeongdong region. In general, the ice clouds tended to exist below around 2~3 km with the consistent easterly flows, and the winds shifted to northerly~northwesterly above the clouds layer. The snow crystal habits observed in the ESSAY campaign were mainly dendrite, consisting of 70% of the entire habits. The rimed habits were frequently captured when two-layered clouds were observed, probably through the process of freezing of super-cooled droplets on the ice particles. The homogeneous habit such as dendrite was shown in case of shallow clouds with its thickness of below 500 m whereas various habits were captured such as dendrites, rimed dendrites, aggregates of dendrites, plates, rimed plates, etc in the thick cloud with its thickness greater than 1.5 km. The dendrites appeared to be dominant in the condition of cloud top temperature specifically ranging $-12{\sim}-16^{\circ}C$. However, the association of snow crystal habits with temperature and super-saturation in the cloud could not be examined in the current study. Better understandings of characteristics of snow crystal habits would contribute to preventing breakdown accidents such as a greenhouse destruction and collapse of a temporary building due to heavy snowfall, and traffic accidents due to snow-slippery road condition, providing a higher-level weather information of snow quality for skiers participating in the winter sports, and estimating more accurate snowfall amount, location, and duration with the fallspeed of solid precipitation.

• 환경영향평가
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• 제2권1호
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• pp.57-63
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• 1993

An analysis for particle settling effects via of plume centerline tilted exponentially under the influence of panicle settling velocity is carried out for particle of $30{\mu}m$ diameter with $1g/cm^3$ density and 0.02m/s settling velocity corresponding to its particle characteristic according to various wind speeds, atmospheric stabilities. Characteristic analysis of surface concentration distribution simulated by Lagrangian model also are carried out under the influence of plume centerline tilted exponentially at 10m stack height emitted 200 particles per second. This study reveals that plume centerline at the nearby source is sharply tilted exponentially under the condition of stable, weakly wind speed, therefore the lower concentration at the nearby source, the higher concentration at the downwind distance far away from source than actual one is brought out, if not apply the effect of plume centerline tilted exponentially to diffusion Model.