Pearl River Delta (PRD) region has experienced fast economic development since 1980s and becomes one of the world’s largest industrial zones and metropolitan areas. However severe air pollution problems such as high concentration of ozone and particulate matter arise with the rapid urbanization and industrial development. According to previous studies, sea-breeze circulation can contribute to pollutant transportation and convective initiation, so it is meaningful to study the dynamical structure of sea-breeze circulations in PRD region. Many researchers have focused on the effects of environmental factors, such as topography, urbanization and background wind, on sea-breeze, but most of them only focused on case studies and did not quantify the characteristics of sea-breeze circulations (including start time, end time, strength, height, occurrence frequency and inland penetrating distance).

In this research a new method to quantify the characteristics of these sea-breeze cases has been identified. The coastal lines in PRD region are simplified into one heptagon which almost covers the Pearl River Estuary and the positive diurnal signals of wind flux over the heptagon are taken as sea-breeze cases. Similarly, the complex coasts along Guangdong province are enclosed by four rectangles and the positive diurnal signals of averaged inshore divergent wind in these four rectangles are considered as sea-breeze cases. This method has been applied to analyze sea-breeze events in 2012 and results indicate that this method can quantify the characteristics of sea-breeze circulations well.

Averaged prognostic variables like temperature gradient, solenoid term and frontogenesis function can be evaluated to illustrate the dynamical process of sea-breeze circulation. Results imply that sea-breeze driven by thermal difference between land and sea can also diminish this temperature difference with vertical motion, in return. During this process, divergence and deformation also has some impacts on sea-breeze circulation. This research can also evaluate the implication of urbanization on sea-breeze circulation quantitatively with frontogenesis function. It is expected that this research will demonstrate the mechanism in which sea-breeze circulation can be modulated by urbanization.