Study of the Pearl River plume dynamics in summer by observation, modeling and remote Sensing

Principal Investigator: Prof. Pan Jiayi

Start Date:	2014/01/01
End Date:	2016/12/31
Type of Grant:	General Research Fund

The discharge of the Pearl River forms a buoyant plume in coastal waters, which is transported eastward from the river mouth and occupies Hong Kong near- and offshore waters, driven by southwesterly winds in summer wet, high-flow season. The river discharge carries inland nutrients and micro-elements into the coastal water area, facilitates a rich primary production area in the Pearl River plume region. Pearl River delta holds one of the densest populations in the world and plays an important role in China rapid development in economy and society.

However, with the rapid economic growth in the river delta and upstream regions, more and more inorganic and organic materials including various kinds of sediments, industrious wasters and sewage are poured into the river, the river water is heavily polluted, and its water quality is getting more and more deteriorated, which greatly threatens ecological environments of the Hong Kong coastal waters). The water equality or bio-physical characteristics of the Pearl River plume are mainly controlled by its dynamic properties such as plume circulations, frontal processes, mixing characteristics. The complex ecosystem in the Hong Kong coastal water cannot be fully unveiled without deep understanding of the plume dynamics. The strongly baroclinic plume can significantly affect the regional ocean circulation. Therefore, investigations of the Pearl River plume dynamics are of great importance for understanding ecological environments and improving numerical simulation and forecast in Hong Kong coastal waters. However, the physical processes of the Pearl River plume have been poorly understood because of insufficient investigations implemented before. In the project, we will investigate the detailed Pearl River plume dynamics, and the objectives are listed as follows:

1. How does the detailed Pearl River plume anatomy respond to the wind forcing and coastal currents? How are the waters of the Pearl River plume classified according to their dynamic and physical properties?
2. What are circulations of the plume water under the influence of summer, southwesterly winds and river discharge? What are the stratification and mixing characteristics in the plume region?
3. What are the dynamic properties of the Pearl River plume fronts, the subcritical versus supercritical? What are the mixing characteristics within the plume frontal region?

The proposed research will focus on gaining new knowledge on the plume dynamics of the Peal River plume and improve in-situ observation database available to relevant Hong Kong government agencies for related applications. The results of the proposed study will enhance our understanding of impacts of the Pearl River plume on ecosystem of the Hong Kong coastal water, and contribute to regional management efforts.

Using the Peal River plume as an example, the analyses carried out by the project will facilitate understanding of processes of similar river plume systems in other regions.