A Three-dimensional Numerical Modeling System in Pearl River Estuary and its Sensitivity Analysis

A three-dimensional numerical modeling system in Pearl River Estuary and its sensitivity analysis

TANG Li-qun¹, SHENG Jin-yu², CHEN Jie¹, LIU Da-bin¹

(1. China Institute of Water Resources and Hydropower Research, Beijing, China, 100048; 2. Dalhousie University, Halifax, NS, Canada, B3H 4J1)

Abstract

A triple Nested-grid three-dimensional coastal circulation modeling system in China sea area is developed based on the Princeton Ocean Model (POM) in this study, including three downscaling subcomponents: a 2D barotropic outer model with an coarse-resolution (～7 km) over China Seas from Bohai Sea to the northern South China Sea, a 3D baroclinic middle model with an intermediate-resolution (～3 km) over the inner shelf of the northern South China Sea, and a 3D baroclinic inner model with an fine-resolution (～1.2 km) over the Pearl River Estuary(PRE) and adjacent coastal waters. The pressure item in the momentum equation is corrected for improving the model running stability and simulation precision using the Semi-Prognostic Method.

The modeling system is calibrated and verified by the tidal level data from Sanzao, Haimen and Beijin stations, the sea-surface temperature from remote sensing analysis and the salinity distributions of winter and summer seasons in the PRE. The circulation during typhoon Koryn in June 1993 is simulated. Four numerical experiments are conducted to determine the main physical processes and to analyze the model sensitivities in the PRE.

Sensitivity analysis shows that the influence of fresh water runoff into the sea on the salinity structure of the estuary is very obvious, but it has little influence on the hydrodynamic structure of the sea area of the Pearl River Estuary. Tides play an obvious role on the currents in the estuary, however, they have little effect outside the estuary due to the control of ocean circulation. Wind stress plays an important role in controlling the surface flow field and the salinity structure of the Pearl River Estuary.

The analysis also shows when the runoff is weakened, the tide is strengthened, and the dynamic contrast is unbalanced, the salinity in the upper reaches of the estuary increases, and the salt water intrusion tends to occur.

Key words: Pearl River Estuary; 3D numerical model; coastal circulation; the structures of temperature/salinity; storm surge； sensitivity