Evaluation for trajectory determination with basin, ridge and sounding meteorological data over a complex terrain

Appropriate modeling transportation of air pollutant is mainly determined by the trajectory prediction, which is based on good meteorological observations and preprocess. However, evaluating the route of pollutant's plume is a difficult task over complex terrains. In Taiwan, for example, pollutants are usually transferred across mountains to reach the basin from nearby coastal regions where power plants, highways and cities located. To predict the reasonable trajectory of pollutant, a modified computational trajectory algorithm was applied in this study. The horizontal wind vector of the trajectory is forced to change directions to travel around the mountains while in stable meteorological conditions or while the mixing height is lower than the mountain height under unstable conditions. The vertical velocities are based on the continuous equation after determining horizontal wind vector at the next step. In determining the trajectory, the meteorological data used from not only surface meteorological stations, but also from a meteorological station on mountain ridge and three vertical profile measurements of tethered-sonde. In addition, Genetic Algorithm (GA) used to calibrate the optimal values for the parameters of the trajectory preprocess. The results show that the trajectories predicted by this algorithm using optimized parameters, ridge and the tethered-sonde meteorological data, and considering about hitting mountains and vertical velocity mechanisms, improve the air quality simulation with better correlation. Although the case study is conducted in Taiwan, the conclusions here are considered valid for others with the same issue in the world.