NALMS Conference Paper: Comparative Study of Heat Exchange Options and Turbulence Closures in Modeling Lake Mendota's Thermal Behavior

Authors: Nguyen T K Linh, Mehrzad Shahidzadehasadi, Thomas J Mathis,
Tran Duc Kien, Bui Minh Hoa, Wei-Cheng Wu, Paul M Craig
Dates: November 5-8, 2024
Location: South Lake Tahoe, CA/NV

Lake Mendota, the largest lake in Madison, Wisconsin, exhibits complex thermal dynamics with pronounced summer stratification and reverse winter stratification under ice. To accurately model these dynamics, it is crucial to understand the impact of heat exchange processes and turbulence closures. This study investigates the effect of different heat exchange options and turbulence closures in EFDC+ on temperature prediction, comparing the outcomes to extensive empirical data.

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The heat exchange analysis examined two methods: Full Heat Balance, COARE 3.6 and the turbulence closure analysis explored four schemes: Mellor-Yamada (EFDC Original Approach), Mellor-Yamada (GOTM), k-ε (GOTM), and k-ω (GOTM). Results were validated against four datasets:

  • The first dataset provided spatially distributed surface sonde measurements from 35 randomized points across four summer seasons, helping evaluate the model's sensitivity in different parts of the lake.
  • The second dataset contained depth profiles from 0 to 20 meters, capturing water temperature. This dataset helped in assessing the model's ability to accurately represent lake stratification and vertical gradients.
  • The third dataset offered continuous measurements from an instrumented buoy located in a deep part of the lake, supplying minutely data on the lake's temperature. This dataset was key to understanding the lake's dynamics over time.
  • The fourth dataset included under ice temperature measurements from 0 to 22 meters at the buoy location, providing data for analyzing the lake's winter stratification.

These results suggest that COARE 3.6 for heat exchange and GOTM-based turbulence closures offer reliable methods for hydrodynamic modeling in freshwater systems like Lake Mendota, yielding more accurate temperature predictions and better representation of complex stratification patterns.

Let us know if you have questions or interest in this topic. We hope to see you at the conference.

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