Observations of visibility and chemical compositions related to fog, mist and haze in south Korea

Since 1970, the yearly consumption of fossil fuel in south Korea has steadily increased to 165 MT from 14 MT. It has been found that the number of days of low visibility (less than or equal to 10 km) was significantly increased by the occurrence of fog, mist and haze. For example, the low visibility days in Seoul during 1989 were over 207 days in comparison with 21 days at a rural site. This similar trend has been observed in other large cities. Ln Chongwon of central Korea, daily measurements of visibility at 09 LST have been made since 1991. It is observed that the increase in the frequency of low visibility days was related to the increase in anthropogenic air pollution and water vapor in the study area. The occurrence of fog-mist-haze was much related to the influence of local, regional and synoptic meteorology. With the increase in both water supply and emission of air pollution, in Korea we commonly observe the typical historical type of London mist and haze. In this study, chemical analyses of fog, mist, haze and frost was carried out. According to analyses of data obtained in 1995, the pH values for 65.9% of all fog and mist samples collected were less than 5.6. The lowest pH value of fog was 4.0. On the other hand, pH values observed for dew and frost in early spring were generally neutral to alkaline in nature, although there was an abundant existence of sulphates and nitrates. This suggests that characteristics of yellow sand and soil dust occurring in spring appear to determine the pH values in hydrometeors occurring on the Korean peninsula. A satellite observation of sea fog is also discussed. It has been observed that the advection fog occurred with air pollutants over the Yellow Sea which were moving out of China.