Abstract. The analysis is presented of the distribution of deep ocean turbulence characteristics on the horizontal scale of order 100 km in the vicinity of the Lifamatola Sill, from the Southern Maluku Sea (north of the sill) to the Seram Sea (south of the sill). The turbulence characteristics were calculated with a regional model of the Indonesian seas circulation based on the Princeton Ocean Model (POM), incorporating the Mellor-Yamada turbulence closure scheme. The analysis has been carried out for the entire Indonesian seas region, including areas around important topographic features, such as the Lifamatola Sill, the North Sangihe Ridge, the Dewakang Sill and the North and South Halmahera Sea Sills. To illustrate results of application of the Mellor-Yamada closure scheme we have focused on the description of features of turbulence characteristics across the Lifamatola Sill because dynamically this region is very important and some estimates of mixing coefficients in this area are available. As is well known, the POM model output provides both dynamical (depth-integrated and 3-D velocities, temperature, salinity, and sea-surface-height) and turbulence characteristics (kinetic energy and master scale of turbulence, mixing coefficients of momentum, temperature and salinity, etc.). As a rule, the analysis of POM modeling results has been restricted to the study of corresponding dynamical characteristics, however the study of turbulence characteristics is essential to understanding the dynamics of the ocean circulation as well. Due to the absence of direct measurements of turbulence characteristics in the analyzed area, we argued the validity of the simulated characteristics in the light of their compatibility with some general principles. Thus, along these lines, vertical profiles of across-the-sill velocities, twice the kinetic energy of turbulence, turbulence length scale, the separate terms in the equation of kinetic energy of turbulence, the Richardson number, and finally coefficients of mixing of momentum and temperature and salinity are discussed. Average values of the vertical mixing coefficient compare well with indirect estimates previously made from diagnostic calculations based on Munk's model.
Semi-Lagrangian semi-implicit time-splitting scheme for a regional model of the atmosphere