Calculating the annual cycle of the vertical eddy viscosity in the North Sea with a three-dimensional baroclinic shelf sea circulation model

The vertical eddy viscosity (Av) is estimated using a three-dimensional baroclinic shelf sea model that treats the temperature as a prognostic quantity. Av is calculated by means of a turbulent closure approach proposed by Kochergin [(1987) Three-dimensional coastal ocean models, American Geophysical Union, pp. 201–208] which is closely related to a Mellor and Yamada [(1974) Journal of Atmospheric Science, 31, pp. 1791–1806] level-2-model that has been used very successfully in a large number of applications. nual cycle of the vertical eddy viscosity is discussed by looking at horizontal and vertical Av-distributions for the year 1988. These examples show that the vertical eddy viscosity is subject to a pronounced annual cycle which can be related to heating and cooling processes as well as to mixing induced by wind and bottom friction. A comparison of these results with Av-distributions calculated for the year 1987 additionally demonstrates a strong inter-annual variability.