A non-hydrostatic dispersion modeling system and its application to air pollution assessments over coastal complex terrain

Abstract

This paper describes an approach to assess air quality over coastal complex terrain. As an example, we report here the results of the air quality assessment of a power plant in the Hongkong–Shenzhen area using regulatory models and an atmospheric dispersion modeling system, respectively. The latter consists of a three-dimensional non-hydrostatic planet boundary layer (PBL) numerical model and a puff diffusion model, and is employed to simulate sea–land breeze circulation and ground-level concentrations (GLC) from an elevated source over the coastal complex terrain. Predictions of PBL model reproduce the meteorological characteristics over complex terrain. The results of GLC from Gaussian dispersion models as National Standard of China and those from the dispersion modeling system show that the concentrations obtained from these two distinctly different methods are of the same order of magnitude. However, compared to the dispersion modeling system, the regulatory models give low GLCs due to the neglect of mesoscale circulation and heterogeneous flow in the region of complex terrain, which are analyzed from the structures of wind and temperature. The results from the two models agree well only when strong sea breeze appears in the daytime. The results of GLC largely depend on the flow patterns, which cannot be simulated in the Gaussian models but can be done in the atmospheric dispersion system. The study suggests the potential of the mesoscale atmospheric dispersion modeling system for studies of air quality in complex terrain.