Application Of E-ε Turbulent Kinetic Energy Closure Thermodynamic Process Lake Model In The East Taihu Lake

In this study, the E-s turbulent kinetic energy closure thermodynamics process lake model is combined with the effect of the submersed macrophyte. The E-ε turbulent kinetic energy closure lake model is driven by using observation data of the Lake Taihu Eddy Flux Network recorded in August 2013. The E-ε turbulent kinetic energy closure lake model is adopted to simulate the lake-air exchanges, thermal structure and dynamical distribution over East Taihu Lake in August 2013, analyzing the lake-air exchange characteristics, water temperature stratification and turbulent mixing movement in submerged macrophyte zone and assessing the effect of the submerged macrophyte. Finally, The E-ε turbulent kinetic energy closure lake model is compared with the CLM4-LISSS lake model.(1) The results show that this model can simulate the lake-air exchanges processes over the shallow lake. The simulated water temperatures, sensible heat flux and latent heat flux are in good agreement with the observations. The RMSE of the sensible heat flux, the latent heat flux are 8.41 W m-2 and 54.7 W m-2,respectively. The E-ε turbulent kinetic energy closure lake model also can well simulate the water temperature, the water temperature calculated by the lake model is compared by the observed values, the RMSE of water temperatures is less than 1℃.(2) Because the water depth is shallow, the weather conditions can impact vulnerably the stratification of the water temperature. The thermal stratification is significant in sunny condition with small wind. The temperature difference between the lake surface and the bottom of the lake is 7.9℃ when the wind speed is 0.8 m s-1. The high wind speed drove the water mixing strongly, then the thermal stratification disappeared. When the wind speed is 12 m s-1, the temperature difference between the lake surface and the bottom of the lake is only 0.12℃.(3) Submerged macrophyte makes it difficult to reach the bottom for the solar radiation, it also can reduce internal heat in the lake, adding resistance to the movement of water, and then influence the distribution of the turbulence kinetic energy and water temperature. When the submersed macrophyte height is 0.4m, the water temperature at 1.5m depth is 0.43℃ higher than the water temperature calculated when the submersed macrophyte height is 1.6m. When the submersed macrophyte biomass density is 100 gDW m-3, the water temperature at 1.5m depth is the largest, which is 0.21℃ higher than the water temperature when the submersed macrophyte biomass density is 1000 gDW m-3.(4) Comparing the E-ε turbulent kinetic energy closure lake model and the CLM4-LISSS lake model, the RMSE of the sensible heat flux and the latent heat flux simulated by the E-ε turbulent kinetic energy closure lake model is lower. The simulated sensible heat flux and the latent heat flux show a strong correlation with the observed heat flux. The correlation coefficients of the sensible heat flux, the latent heat flux simulated by the E-ε turbulent kinetic energy closure lake model are 0.02 and 0.03 higher, respectively. The water temperature simulated by the E-ε turbulent kinetic energy closure lake model is lower than the observed values, while the water temperature simulated by the CLM4-LISSS lake model is larger. The results indicate that the E-ε turbulent kinetic energy closure lake model can better consider the effect of the submersed macrophyte and simulate more accurately in the East Taihu lake.