Calculation of vertical profiles of lake‐averaged temperature and diffusivity in Lakes Ontario and Washington

By using statistical analysis of temperature observations and model calculations, the common parameterization of vertical eddy diffusivity ( k ) in terms of the gradient Richardson number ( Ri ) is simplified. The simpler formulation accurately reproduces seasonal variations in temperature profiles from Lakes Ontario and Washington. Energy arguments support use of the simplified parameterization and suggest use of a modified Ri in calculating k . The new expression for k resulted in more realistic estimates of thermocline k . The modeling of free convective mixing in Lake Ontario by heat conservation resulted in excessive temperatures in the hypolimnion during fall overturn.