Wind information is one of the major inputs for the prediction of urban air flow using computational fluid dynamic (CFD) models. Therefore, the numerical characteristics of the wind data formed at their mother domains should be clarified to predict the urban air flow more precisely. In this study, the formation characteristics of the wind data in the Seoul region were used as the inlet wind information for a CFD based simulation and were analyzed using numerical weather prediction models for weather research and forecasting (WRF). Because air flow over the central part of the Korean peninsula is often controlled not only by synoptic scale westerly winds but also by the westerly sea breeze induced from the Yellow Sea, the westerly wind often dominates the entire Seoul region. Although simulations of wind speed and air temperature gave results that were slightly high and low, respectively, their temporal variation patterns agreed well with the observations. In the analysis of the vertical cross section, the variation of wind speed along the western boundary of Seoul is simpler in a large domain with the highest horizontal resolution as compared to a small domain with the same resolution. A strong convergence of the sea breeze due to precise topography leads to the simplification of the wind pattern. The same tendency was shown in the average vertical profiles of the wind speed. The difference in the simulated wind pattern of two different domains is greater during the night than in the daytime because of atmospheric stability and topographically induced mesoscale forcing.

To predict diffusion and movement of air pollutants in coastal urban region a numerical simulation shoud be consider atmospheric flow field with land-sea breeze, mountain-valley wind and urban effects. In this study we used Lagrangian particle dispersion method in the atmospheric flow field of Pusan coastal region to depict diffusion and movement of the pollutants emited from particular sources and employed two grid system, one for large scale calculating region with the coarse mesh grid (CMG) and the other for the small region with the fine mesh grid (FMG). It was found that the dispersion pattern of the pollutants followed local circulation system in coastal urban area and while air pollutants exhausted from Sasang moved into Baekyang and Jang moutain, air pollutants from Janglim moved into Hwameong-dong region.