The thermal bar

Abstract

A study is made of the thermally induced transitory boundary region, called the thermal bar, between two stratified fluids, one in direct and the other in reverse stratification. Approximate solutions are found by using double perturbation expansions. The results show a dominant meridional cyclonic flow along the perimetric edge of the lake and an anticyclonic flow in the middle portion of the lake. The zonal and the vertical velocity components form a four-celled circulation with sinking motion along the thermal bar and upwellings in the middle as well as at the edges of the lake. Both the temperature distribution and the velocity field of the theoretical solutions agree very well with field observations. The thermal bar circulation is found to strongly inhibit the horizontal exchange between shallow edge water and deep open-lake water. The insulative characteristics of the thermal bar do not only affect the physical, chemical, and biological environment of the lake water, but also impose a more serious water pollution consequence along the beach.