• Title, Summary, Keyword: visibility

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The Characteristics of Visibility Measured by Forward Scattering Meter on Summertime in Pusan (Forward Scattering Meter 측정에 의한 부산의 하계 시정 특성)

  • 김유근
    • Journal of Environmental Science International
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    • v.9 no.5
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    • pp.385-388
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    • 2000
  • Visibility reduction is a barometer of air pollution which people can notice easily. First of all we need to measure quantified visibility continuously in order to examine visibility reduction. Prevailing visibility is not practical to measure visibility depending on observer's expertness. Scattering visibility using Forward Scattering Meter(Belfort Visibility Sensor 6230) has been measured at Kwangan-Dong in Pusan and analysed since July 1998. According to the analysis the correlation coefficient(R) between prevailing visibility and scattering visibility was 0.7235. The visibility appeared that each frequency of poor visibility(under 6km) and good visibility(over 25km) was 10.6%, 9.7% on summertime in Pusan and the visibility range from 10km to 20km ranked high frequency as a half of whole ranges. The order of correlation coefficients between visibility an air pollutants are ranking CO. PM10 and NO2 that values are 0.5878, 0.5369,l 0.5284 respectively. In meteorolgical factor the case of poor visibility presented more weakly wind speed and higher relative humidity than the case of good visibility. The correlation coefficient between calculated visibility of multiple linear regression model and observed visibility was 0.7215. But the trend of calculated and observed visibility variation was similar with the exception of several good visibility cases.

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A Comparative Study on the Visibility Characteristics of Naked-Eye Observation and Visibility Meters of Fog over South Korea (남한에서의 안개 사례별 목측과 시정계 계측의 시정 특성 비교)

  • Lee, Hyun-Kyoung;Suh, Myoung-Seok
    • Atmosphere
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    • v.28 no.1
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    • pp.69-83
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    • 2018
  • Most of the researches on fog in South Korea have been done based on the naked-eye observation but the number of observation sites is just 22. Considering the localities of fog and various durations, it is essential to utilize more than 250 visibility meters that measure visibility every minute. In this study, the visibility characteristics of visibility meters were compared with that of the naked-eye observation using one year data, 2016, and radiation fog and advection fog cases were analyzed in detail. The concordance rate of the two data set was 0.96~0.97, but discordance rate was 0.19~0.47. In general, visibility meters observed fog more frequently than naked-eye. The correlation between two data sets is clearly dependent on the visibility and geographic locations (fog/thick fog (< 100 m) of inland: 0.86/0.61; fog/thick fog: 0.65/0.73 of island/coastal site). In both fog cases, the fog events observed by naked-eye were consistently detected by visibility meters, and visibility meters clearly well detected very short fog/thick fogs. Formation and dissipation time of fog for the fog cases were similar but fog duration by visibility meters was shorter because of exclusion of temporary dissipated time. In addition, the visibility meters showed a detailed distribution of fog events that occurred simultaneously over South Korea. It would be useful to analyze the spatial and temporal characteristics of, in particular, thick fog using visibility meters. However, more works are needed for the filtering criteria for analyzing fog using visibility meters alone.

A Study on the Relationship between Supply Chain Visibility, Win-Win Cooperative Supply Chain, and Supply Chain Performance (공급사슬 가시성, 상생협력 공급사슬, 공급사슬 성과 간의 관계에 대한 연구)

  • Park, Chan Kwon
    • Journal of the Korean society of supply chain management
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    • v.17 no.2
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    • pp.75-87
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    • 2017
  • The main purpose of this study is to investigate the relationship between supply chain visibility, win-win cooperation supply chain, and supply chain performance. The results of the test are as follows. First, the sensing visibility, learning visibility, and adjustment visibility selected as supply chain visibility all have a positive(+) effect on the win-win cooperation supply chain. And the win-win cooperative supply chain has a positive(+) effect on the supply chain performance. Finally, the mediating effect of the win-win cooperation supply chain was tested and found to have some mediating effect. As a result of analyzing the relationship between supply chain visibility, win-win cooperative supply chain, and supply chain performance, improvement of supply chain visibility can enhance the level of win-win cooperation supply chain, and can also improve supply chain performance. It emphasizes the need for securing supply chain visibility for individual companies.

Visibility Impairment by Atmospheric Fine Particles in an Urban Area

  • Kim, Young J.;Kim, Kyung W.
    • Journal of Korean Society for Atmospheric Environment
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    • v.19 no.E3
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    • pp.99-120
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    • 2003
  • Visibility impairment in an urban area is mainly caused by airborne fine particulate matters. Visibility in a clean air environment is more sensitive to the change of PM$_{2.5}$ particle concentrations. However, a proportionally larger reduction in fine particle concentration is needed to achieve a small increment of visibility improvement in polluted areas. Continuous optical monitoring of atmospheric visibility and extensive aerosol measurements have been made in the urban atmosphere of Kwangju, Korea. The mean for fine particulate mass from 1999 to 2002 at Kwangju was measured to be 23.6$\pm$20.3 $\mu\textrm{g}$/㎥. The daily average seasonal visual range was measured to be 13.1, 9.2, 11.0, and 13.9 km in spring, summer, fall, and winter, respectively. The mean light extinction budgets by sulfate, nitrate, organic carbon, and elemental carbon aerosol were observed to be 27, 14, 22, and 12%, respectively. It is highly recommended that a new visibility standard and/or a fine particle standard be established in order to protect the health and welfare of general public. Much more work needs to be done in visibility studies, including long-term monitoring of visibility, improvement of visibility models, and formulating integrated strategies for managing fine particles to mitigate the visibility impairment and climate change.e.

On Air Pollution and Visibility Reduction in Seoul (서울의 대기오염과 시정감소)

  • 최정숙;정용승
    • Journal of Korean Society for Atmospheric Environment
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    • v.9 no.1
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    • pp.51-60
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    • 1993
  • In order to study on the cause of visibility aggravation, we have selected the days of low-visibility observed in Seoul with haziness that was below 6km from 12 to 15 LST. According to the examinations, the number of low-visibility days satisfying the criteria is 30 days in 1989, 39 days in 1990, and 35 days in 1991, respectively. The annual number of low visibility days appears to increase mainly due to an increase in emission of air pollutants and in anthropogenic water vapor in the biosphere. The relationship between visibility and air pollutants(TSP, $NO_2, SO_2, O_3$) of selected days is also studied. Air pollution concentrations of selected days are much higher than those of other days. It is observed that the cause of visibility aggravation in Seoul is mainly smog and air pollutants. In particular, the visibility reduction and high $SO_2$ concentrations at Seoul in winter are similar phenomena that occurring with London smog, while the visibility reduction and high $O_3$ concentrations at Seoul in summer are also similar to the type of Los Angeles smog.

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Predictability Experiments of Fog and Visibility in Local Airports over Korea using the WRF Model

  • Bang, Cheol-Han;Lee, Ji-Woo;Hong, Song-You
    • Journal of Korean Society for Atmospheric Environment
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    • v.24 no.E2
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    • pp.92-101
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    • 2008
  • The objective of this study is to evaluate and improve the capability of the Weather Research and Forecasting (WRF) model in simulating fog and visibility in local airports over Korea. The WRF model system is statistically evaluated for the 48-fog cases over Korea from 2003 to 2006. Based on the 4-yr evaluations, attempts are made to improve the simulation skill of fog and visibility over Korea by revising the statistical coefficients in the visibility algorithms of the WRF model. A comparison of four existing visibility algorithms in the WRF model shows that uncertainties in the visibility algorithms include additional degree of freedom in accuracy of numerical fog forecasts over Korea. A revised statistical algorithm using a linear-regression between the observed visibility and simulated hydrometeors and humidity near the surface exhibits overall improvement in the visibility forecasts.

On Relationship of Low Visibility to Air Pollution in Cities (도시의 대기오염과 시정감소에 관하여)

  • 정용승;김태군;정재섭
    • Journal of Korean Society for Atmospheric Environment
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    • v.8 no.1
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    • pp.1-6
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    • 1992
  • Using data measured in 1989, a study on variations of visibility and air pollution observed in Seoul, Chongju and Choopoongryong is carried out. Analysis includes on low visibility (< 10km) and smog occurring in the Metropolitan Seoul. It was observed that number of days of visibility less than 10km during 1989 was 56.7% (207 days) for Seoul, 45.7%(167 days) for Chongju and 5.8% (21 days) for Choopoongryong. Chongju is a medium size city (population : a half million) and Choopoongryong is a rural site. In the urban are as, however, the number of low visibility days was relatively large during the winter but with little seasonal variations. In each month these cities recorded more than 10 days of low visibility. The visibility reduction due to mist, fog and haze been occurred with air pollution. In particular, the reduction in a cold season related with an increase in high concentrations of $SO_x$ and aerosols. This type of low visibility occurring in Seoul is a similar type that is occurring in London, U.K. On the other hand, the visibility reduction during in a warm season is related with high concentrations of NOx and other photochemical precursors. The visibility reduction in Seoul during summer is the same type occurring in Los Angeles, U.S.A.

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On the Origin of Visibility Degradation in Seoul (서울지역의 시정 장애 요인에 관한 연구)

  • 윤순창;이강웅
    • Journal of Korean Society for Atmospheric Environment
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    • v.14 no.3
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    • pp.229-236
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    • 1998
  • Visibility is a good indicator of comprehensive alto quality. The prevailing visibility in Seoul is no better than the past although the average concentration of SO2 and TSP (total suspended particulate) has decreased quite significantly in the past decade, owing to the government efforts to reduce the emission. Then, a question arises why visibility has not been improved. In order to answer this question we have investigated which components of air pollutants are most responsible for the visibility degradation in Seoul. Analysis on the visibility vs the aerosol sixte distribution measured by an optical particle counter shows that the particles of the size interval between 0.5mm and 2.5mm are most responsible for the visibility degradation. Among the criteria air Pollutants, NOB concentration is found to be moot responsible, rather than PM10. ton analysis of the particulate collected by a high volume sampler shows that the nitrate component increases more significantly than other ions when visibility becomes very poor. Therefore, we conclude that the major causes of visibility degradation in Seoul are the increase of NOB, nitrates and the particles of the size range between 0.5mm and 2.5mm.

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Analysis of Image Visibility in Projection-type Integral Imaging System without Diffuser

  • Park, Soon-Gi;Song, Byoung-Sub;Min, Sung-Wook
    • Journal of the Optical Society of Korea
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    • v.14 no.2
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    • pp.121-126
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    • 2010
  • We analyze image visibility of a projection-type integral imaging system without diffuser, in terms of the fill factor, which is determined by the relationship between the exit pupil of the projection system and the size and the focal length of the elemental lens. High fill factor is a requirement for good visibility. Moreover, for psychological reasons, for the same fill factor, better visibility is accomplished using a relatively small elemental lens. In this paper, we study image visibility through basic experiments and results.

Long-term Trends of Visibility and Air Quality in Seoul, Ganghwa, Susan, Gwangju, Jeju (서울, 강화, 서산, 광주, 제주지역에서의 장기간 대기오염 및 시정 변화경향에 대한 연구 : 1990년 1월~2001년 7월)

  • Han, J.S.;Moon, Kwang-Joo;Kong, B.J.;Hong, Y.D.;Lee, S.J.;Shin, J.Y.
    • Journal of Environmental Impact Assessment
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    • v.13 no.4
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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.