Abstract: A Weather Research and Forecasting Model (WRF) and random walk model have been used to numerically-simulate and analysis the characteristics of mesoscale wind field and atmospheric diffusion in coastal area of a site. The results indicated that the atmospheric dispersions in this area is determined both by synopic systems and land-sea breeze circulation. Spatial variation of wind field is not obvious in synopic systems situation, which leads to the straight dispersion plume. Temporal variation of wind field, particularly the wind direction transition caused by transient of land-sea breezes, plays an important role in atmospheric diffusion. The method of random walk simulation better reflects the local atmospheric diffusion characteristics, especially in complex terrain and neutral stability situation, windward slope also appears high concentration distribution.

Key words: air diffusion, numerical simulation, WRF model, random walk model