干旱区生态环境知识资源中心

Historical records in association with Asian dust events were retrieved from ancient Korean literature, which in conjunction with modern observations, indicate that dust events have occurred most frequently in the springtime during the last two centuries. Recent observations through surface network exhibit that Asian dust took place more often in the western part of the Korean peninsula over the last 20 years. In this study, two dust cases, April 1998 and January 1999, were selected to examine detailed conditions most favorable for dust generation, emission, and transport to Korea and to investigate the effect of dust particles on physical and optical properties of aerosols collected in Seoul. Dust transported to the Korean peninsula is closely linked to dust storms generated in upstream regions of the Yellow River or Manzurian plain, which are known as main source regions. Judged from synoptic conditions for both spring and winter dust events, meteorological settings favorable for dust emission are high surface winds and baroclinic instability at 1.5 km level. A strong wind belt, formed at a 5 km level, expedites dust transport, and this is typically much faster in winter. It was confirmed from a backward trajectory analysis that the air carrying mineral dust particles originated from deserts in central Asia and in 1 day passed through the Korean peninsula during wintertime. The effect of mineral dust on aerosol particles is well depicted in the size-separated number concentrations of aerosols observed in Seoul. In both cases, concentrations of coarse particles larger than 0.82 mum were distinctly enhanced while those of fine particle smaller than 0.5 mum were reduced. The measurements of optical depth also indicate that the atmosphere is more turbid with larger particles during dust events.