University of Waterloo
Waterloo, Ontario, Canada
Presented in this paper is a second-order turbulence closure scheme for modelling the oceanic mixed-layer. While the scheme is similar in some respects to a Mellor-Yamada level 2.5 scheme, it differs in the treatment of the turbulent fluxes. The modelling equations consist of a set of conservation equations for the mean velocity, temperature and salinity. To estimate the level of turbulence taking place, an equation for the mean turbulent kinetic energy (TKE) is also solved. In order to determine how well the model can simulate the diurnal time scale, the model was tested against observational data taken from the LOTUS experiment. This refers to a long-term (2 year) upper ocean study which began in May 1982 and was conducted in the Sargasso Sea located at $34^{\circ} N$ and $70^{\circ} W$ in the North Atlantic. With this data an 8 day simulation was carried out beginning on July 13, 1982. This particular period was chosen because the atmospheric forcing is characterized by weak winds, strong solar heating and little horizontal advection and hence is well suited for testing the one dimensional model. Due to the strong solar heating and very weak winds the observed near surface temperature undergoes large amplitude diurnal warming events which the model was able to reproduce. Both observations and simulations will be presented.