Synopsis, transport, and physical characteristics of Asian dust in Korea

Historical records in association with Asian dust events were retrieved fro m 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 Ko rean peninsula over the last 20 years. In this study, two dust cases, April 1998 and January 1999, were selected to examine detailed conditions most f avorable for dust generation, emission, and transport to Korea and to inves tigate the effect of dust particles on physical and optical properties of a erosols collected in Seoul. Dust transported to the Korean peninsula is clo sely linked to dust storms generated in upstream regions of the Yellow Rive r or Manzurian plain, which are known as main source regions. Judged from s ynoptic conditions for both spring and winter dust events, meteorological s ettings favorable for dust emission are high surface winds and baroclinic i nstability at 1.5 km level. A strong wind belt, formed at a 5 km level, exp edites 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 concent rations of aerosols observed in Seoul. In both cases, concentrations of coa rse particles larger than 0.82 mum were distinctly enhanced while those of fine particle smaller than 0.5 mum were reduced. The measurements of optica l depth also indicate that the atmosphere is more turbid with larger partic les during dust events.