Reconsideration of wind stress, wind waves, and turbulence in simulating wind-driven currents of shallow lakes in the Wave and Current Coupled Model (WCCM) version 1.0

Abstract

Wind stress, wind waves, and turbulence are essential variables and play a critical role in regulating a series of physical and biogeochemical processes in large shallow lakes. However, the parameterization of these variables and simulation of their interactions in large shallow lakes have not been strictly evaluated owing to a lack of field observations of lake hydrodynamic processes. To address this problem, two process-based field observations were conducted to record the development of summer and winter wind-driven currents in Lake Taihu, a large shallow lake in China. Using these observations and numerical experiments, a Wave and Current Coupled Model (WCCM) is developed by rebuilding the wind drag coefficient expression, introducing wave-induced radiation stress, and adopting a simple turbulence scheme to simulate wind-driven currents in Lake Taihu. The results show that the WCCM can accurately simulate the upwelling process driven by wind-driven currents during the field observations. A comparison with a reference model indicates a 42.9 % increase of the WCCM-simulated current speed, which is mainly attributed to the new wind drag coefficient expression. The WCCM-simulated current direction and field are also improved owing to the introduction of wave-induced radiation stress. The use of the simple turbulent scheme in the WCCM improves the efficiency of the upwelling process simulation. The WCCM thus provides a sound basis for simulating shallow lake ecosystems.