AN OCEAN LARGE-EDDY SIMULATION-MODEL WITH APPLICATION TO DEEP CONVECTION IN THE GREENLAND-SEA

A nonhydrostatic, Boussinesq, three-dimensional model, the ocean large -eddy simulation model (OLEM), has been developed to study deep oceani c convection. The model uses a subgrid-scale parameterization of turbu lence developed for large-eddy simulation models, and the advection of scalars is accomplished using a monotonic scheme. A set of experiment s was performed using OLEM to provide a direct comparison with laborat ory results and aircraft measurements of the atmospheric convective bo undary layer. The results from these experiments are in excellent agre ement with laboratory and atmospheric convective boundary layer measur ements of the mean profiles of zonal and vertical velocity variance, p otential temperature variance, and heat flux. The horizontal wavenumbe r spectra of zonal and vertical velocity are also in good agreement wi th laboratory measurements and Kolmogorov's theoretical inertial subra nge spectrum. A set of experiments using a potential temperature-salin ity profile from the central Greenland Sea for model initialization wa s conducted to study the effect of the thermobaric instability and rot ation on the structure and evolution of deep oceanic convection. The a rtificial removal of the thermobaric instability suppresses penetrativ e convection, which is responsible for rapid changes in water properti es at depths much greater than occurs for convective, mixed-layer deep ening. The vertical velocity and diameter, -0.08 m s(-1) and 300 m, re spectively, of the penetrative plumes are in good agreement with obser vations from the Greenland Sea. A period of strong penetrative convect ion is followed by a gradual transition to convective, mixed-layer dee pening. During penetrative convection the values of heat flux are abou t 2 times greater than convective, mixed-layer deepening. In the absen ce of rotation the evolution of penetrative convection occurs more rap idly, and vertical motions are more vigorous. The presence of the hori zontal component of rotation forces asymmetries in the circulation aro und a penetrative plume. These experiments clearly demonstrate the imp ortance of thermobaric instability and rotation on deep convection. To properly model large-scale flows in regions of penetrative convection , it is necessary to include these effects in the vertical mixing para meterization.