Temporal and Spatial Characteristics of Visibility in North Korea

Temporal and spatial trends of the visibility in North Korea (NK) were studied to further understand the air quality in NK. The data from 27 observation stations in NK sent through the Global Telecommunication Service (GTS) of the World Meteorological Organization (WMO) were used. These stations are classified into five groups based on the visibility characteristics. Other parameters such as relative humidity, wind speed, temperature, and the annual average PM2.5 concentration were also used to characterize the visibility data. Generally, the visibility of NK has increased over the last 40 years. The visibility of NK was low in summer and morning and high in winter and afternoon, respectively. It is mainly due to weather conditions, visibility tends to be low in conditions with high relative humidity and low wind speed. However, it is difficult to explain the reasons why the visibility in summer afternoon was higher than winter afternoon. There were regional differences. For example, Pyongyang group only showed decreasing trend and Chagang group showed very low visibility. Differences in the weather conditions, air pollution level, and other factors such as change of observation method might give effects on the regional difference. And further study directions are suggested shortly.