This dissertation focuses on investigating the feature and mechanism of local and regional scale atmospheric circulations and its associated pollution transport and trapping in the Pearl River Delta (PRD) region, which is a highly urbanized area with complex terrain and coastlines....[ Read more ]

This dissertation focuses on investigating the feature and mechanism of local and regional scale atmospheric circulations and its associated pollution transport and trapping in the Pearl River Delta (PRD) region, which is a highly urbanized area with complex terrain and coastlines.

The first step of this research was to set up a localized fine-scale (1 km) land-surface/urban modeling system coupled with the mesoscale meteorological model MM5, to provide a more accurate and realistic prediction of meteorological condition over the region. After the model evaluations, a number of numerical experiments have been conducted in order to understand the impact of urbanization and its associated urban heat islands on meteorology over the PRD. The modeling system was then coupled with a particle trajectory model to demonstrate the unique land-sea breeze circulation features and the temporal evolution, and develop a conceptual model for the air pollution trapping phenomenon in the region. Further sensitivity experiments were used to illustrate the impact of urbanization and large-scale flows on the pollution processes.

After that, a new methodology was introduced to identify the contribution of primary and secondary pollutants from the emissions of local/regional area sources and power plants to Hong Kong. Several weighting factors were established to the air mass/pollutant trajectory calculations and used to evaluate the local and regional contribution of primary pollutants to Hong Kong pollution. The relationships between emission inventories, physical paths and chemical transformation rates of the pollutants, and observational measurements were formulated. The local and regional contributions of secondary pollutants were obtained by this conceptual module.

Finally, this study challenges the backward trajectory analysis, which is a well accepted analytical method in air quality research in Hong Kong. The result demonstrates large uncertainties in their behavior when comparing calculations using different resolution of wind fields, indicating that care must be taken on choosing the suitable resolution of wind fields when calculating trajectories for diagnostic studies.