Hee-Jin In

Estimation of Dust Emission Amount for a Dust Storm Event Occurred in April 1998 in China

The threshold friction velocities for dust rises in inland China are examined using WMO synoptic station data and the soil types in the source region to estimate dust emission amounts for a dust event occurred from 13 to 24 April 1998 in China. The dust-rise reports in the WMO synoptic data are used for the delineation of dust source regions that are found to be composed of the Gobi, Sand and Loess regions according to soil types in inland China. The estimated threshold friction velocities with the use of wind speeds observed in the Gobi, Sand and Loess regions are found to be about 60, 50, and 40 cm s-1, respectively. The estimated dust-rise occurrencegrids by both the grid interpolated observed wind and the MM5 model wind well coincide with the areas of strong wind speeds. However, the dust-rise areas estimated by the model are larger than those estimated by the observed wind, whereas the friction velocities estimated by the model in the dust-rise areas are much smaller than those estimated by the observed wind, which result in less amount of dust emission by the model in all source regions. The 10-day accumulated total dust emission estimated by the observed wind during the dust storm event is found to be 4.64 × 108 ton in the whole source region of 3.29 × 106 km2. Of which 85, 9 and 6% are, respectively, contributed by the Gobi, Sand and Loess regions,suggesting the dominant emission from the Gobi region for this event.The model estimated total dust emission is found to be about 56% of that estimated by the observed wind, indicating some improvement of the model being required.

Simulation of long-range transport of acidic pollutants in East Asia during the Yellow Sand event

Abstract The atmospheric chemical process was simulated using the Carbon Bond 4 (CB-4) model, the aqueous-phase chemistry in Regional Acid Deposition Model and the thermodynamic equilibrium relation of aerosols with the emission inventories of the Emission Database for Global Atmospheric Research, the database of China and South Korea and the Mesoscale Model version 2 (MM5) meteorological fields to examine the spatial distributions of the acidic pollutant concentrations in East Asia for the case of the long-lasting Yellow Sand event in April 1998. The present models simulate quite well the observed general trend and the diurnal variation of concentrations of gaseous pollutants, especially for O3 concentration. However, the model underestimates SO2 and NOx concentration but overestimates O3 concentration largely due to uncertainty in NOx and VOC emissions. It is found that the simulated gaseous pollutants such as SO2, NOx, and NH3 are not transported far away from the source regions but show significant diurnal variations of their concentrations. However, the daily variations of the concentrations are not significant due to invariant emission rates. On the other hand, concentrations of the transformed pollutants including SO42−, NH4+, and NO3− are found to have significant daily variations but little diurnal variations. The model-estimated deposition indicates that dry deposition is largely contributed by gaseous pollutants while wet deposition of pollutants is mainly contributed by the transformed pollutants.

Parameterization of wet deposition of sulfate by precipitation rate

A method for the estimation of wet deposition of sulfate is developed using routinely available meteorological data and the observed airborne sulfate concentration. This approach takes into account different mechanisms of precipitation formation that determine sulfate concentration in precipitation water. Four different precipitating cloud types, including cold cloud, warm cloud, stratified layered cloud and convective cloud, according to their precipitation formations are incorporated differently to estimate sulfate concentration in precipitation water. This method is implemented to estimate wet deposition of sulfate in Seoul for the days when the airborne sulfate concentration is available. The estimated wet deposition of sulfate shows that the model slightly overestimates the wet deposition of sulfate especially for the warm cloud case while it does underestimate sulfate deposition for the Bergeron process in developing precipitation particularly when the input airborne sulfate concentration is small. The precipitation amount weighted mean wet deposition of sulfate obtained from the model, overestimates that observed by a factor of 1.6 for this case study. This discrepancy might be associated with non-steady revolutional features of precipitating clouds and the resolvable scaling difference between the model and observation.

Long-Range Transport of a Severe Asian Dust (Yellow Sand) Observed in Korea During 21–23 March in 2002

Yellow Sand (Asian dust), which is a typical example of mineral aerosol frequently originates in the Sand desert, Gobi desert and Loess plateau in Northern China and Mongol during the spring season (In and Park, 2002). A severe dust storm was observed in Korea during 21–22 March in 2002. The maximum concentration of PM10 observed in the air pollution monitoring sites scattered over South Korea exceeded 1,000 μg m−3 which is more than 10 times higher than that of the non-dust storm period.