Observed relationships between microstructure patches and the gradient Richardson number in a thermally stratified lake

Microstructure profiles of velocity and temperature were collected in Lake Kinneret during the summer months of 1997, 1998, 1999 and 2001 using the Portable Flux Profiler. The profiles were analysed to determine the turbulent properties within statistically homogeneous microstructure patches that were identified in each profile. The nature of the turbulent properties and their distribution is discussed in terms of the dominant forcing mechanisms that exist through the water column. It was found that the properties of binned patch data collapsed reasonably into log-linear functions of the gradient Richardson number Rig with changes in behaviour at Rig = 0. 03 and 0. 2. For Rig <0. 03 the observations were dominated by boundary turbulence and law-of-the-wall approximations were shown to provide a good description of the observed data near the lake surface. For 0. 03