Numerical study of Jiulongjiang river plume in the wet season 2015

Numerical simulation of the buoyant river plume in the Jiulongjiang River (JR) estuary, China, and its shelf in a wet season, April-September 2015, is constructed and applied to explore the evolution of the JR plume. The model is forced with realistic forcing, including river discharge, tides, wind stress, surface heat flux and freshwater flux, and ocean open boundary conditions. The simulation results agree well with in-situ and satellite observations. A Lagrangian particle tracking method is used to identify the freshwater pathway. It is found that the JR freshwater tends to escape the estuary-shelf system to the north from April to mid-August but to the south since late August. Based on a self-organizing map (SOM) analysis, four major JR patterns are identified. A northeastward plume pattern has the highest frequency of occurrence (44.8%), while a southwestward plume pattern has the second highest frequency of occurrence (33.9%). The other two patterns are transitional. The analysis of the alongshore and cross-shore momentum balances indicates that the JR plume is largely shaped by wind and background alongshore current. Particularly, the background coastal current plays an important role for the JR freshwater escape to the north in the Taiwan Strait.