Surface turbulence in natural waters: A comparison of large eddy simulations with microstructure observations

Turbulent properties of the surface layer of stratified lakes have been qua ntified from temperature microstructure measurements made during convective conditions. Large eddy simulations have been performed using corresponding surface boundary conditions. We compare rates of dissipation of turbulent kinetic energy and dissipation of temperature variance obtained from observ ations with those obtained from large eddy simulations. While profiles of t he rate of dissipation of turbulent kinetic energy can be reproduced very w ell by the model, the rate of dissipation of temperature variance exhibits smaller values in the calculations. Other statistical characteristics of tu rbulence agree for both properties. We show that part of the discrepancy de rives from large-scale lateral advection, which is not represented by the m odel, while turbulence on the microscale is reproduced well.