Characteristics of the Sea-Breeze Circulation in the Pearl River Delta Region and Its Dynamical Diagnosis

摘要

The Pearl River delta (PRD) region has experienced rapid economic development since the 1980s and has become one of the world's largest industrial zones and metropolitan areas. Previous studies have shown that the sea-breeze circulation can contribute to pollutant transportation and convective initiation, so it is useful to study the dynamic structure of the sea-breeze circulation in the PRD region. Many researchers have focused on the effects of environmental factors, such as topography, urbanization, and background wind, on the sea breeze, but most focused only on case studies and did not quantify the characteristics of the sea-breeze circulation climatologically. In this study, a sea-breeze identification metric was defined to identify sea-breeze events from WRF simulation data of 2012 and quantify their characteristics, including their start time, end time, strength, height, frequency, pumping ability, and inland-penetrating distance. The results indicate that this method works well to identify and quantify the sea-breeze events of 2012. It is found that the solenoid term, the largest positive contributor to vorticity acceleration, is mostly modulated by the temperature gradient. Therefore, the frontogenesis of the sea-breeze front is discussed in this study. The result shows that offshore background wind that increases frontogenesis is favorable to the development of the sea breeze, but it also prevents it from propagating vertically and horizontally.