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KMID : 0896219990190010137
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Journal of Daegu Health College
1999 Volume.19 No. 1 p.137 ~ p.153
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Affecting Factors on Variations and Long-trends of the Atmospheric Visibility in the Metropolitan Area of Taegu
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Kim Moo-Sik
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Abstract
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This study was carried out to investigate the affecting factors on variations and long-trends of the atmospheric visibility in the metropolitan area of Taegu. To compare visibility data based on human observation of the perceptibility of targets, the most comprehensive sets of long-term air quality and meteorological data were used. The air quality and meteorological data was measured at 5 sites of local air quality monitoring networks and Taegu Weather Station during the last 8 years(1990~1997), respectively. Diurnal variations of visibility were low at night and high in the daytime. Also it was found to exhibit substantial seasonal variations, lower in winter and summer seasons than in spring and fall. In the long trends, visibility impairment was slightly reduced to lower levels between early 1990 and 1997. Analysis includes low(12㎞) and poor(5㎞) visibility measured at 3:00 pm. It was observed that the number of days for low visibility was 594 days(20.3%) and poor visibility was 36 days(1.2%) during the last 8 years(2922 days). The number of days for low visibility and rainy days in this period was 203 days(6.9%). Visibility reductions in springtime was responsible for particulate matter emissions, whereas impairment visibility in summertime was due to photochemical smog. It could be assumed that it shows symptoms of photochemical smog when the atmospheric ozone concentration was slightly increased and nitrogen dioxide started to decrease under strong solar radiation. Reductions of the visibility in late fall and early winter were complexly affected by fossil combustion-related emissions such as particulate matter, nitrogen dioxide, sulfur dioxide and microclimatological factors such as radiation inversion layer formation near the earth’s surface.
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