Boundary model with two-equation turbulence parameterization

The quantitative description of a baroclinic stratified geophysical boundary layer (GBL) in the atmosphere (ABL) and in the ocean (OBL) uses hydrodynamic equations for a mean flow and requires a solution of a turbulence closure problem. We developed an improved turbulence parameterization. The existing turbulence models differ in completeness of included physical mechanisms, and number of the equations for the turbulence parameters. The most important characteristics of turbulence are turbulent kinetic energy (TKE) and dissipation rate (DR). The comprehensive closure schemes usually use evolutionary equations for TKE and DR. We improved the two-equation closure model (with equations for TKE and DR) by accounting for transport, pressure correlation, and horizontal turbulence production. This two-equation scheme allowed to calculate the mean fields-turbulence and turbulence-turbulence parts of velocity-pressure correlation. The physically justified boundary conditions were formulated for TKE and DR. The improved equations for TKE and DR described the basic properties of turbulent exchange in GBL better than the usually used parameterizations. The semi-implicit numerical integration method for the closed system of GBL equations was used. The positively defined numerical approximation was developed for the TKE and DR equations. The improved turbulence parameterization was used for the solution of the applied problems related to ABL and OBL. The results of reconstruction of ABL and OBL were compared with measurements of hydrometeorological network and polygon experiments. It was shown that model results of the ABL and OBL internal structure reconstruction compared favorably with observations. The 3D simulated fields of the meteorological and the turbulence parameters in ABL were discussed for the typical synoptic situations. The OBL structure was calculated for a climatological distribution of atmospheric surface wind. The 3D distributions of the sea currents was obtained for coastal area. The ABL parameterization was implemented in the operational forecast model. This improved model forecast of the meteorological variables and weather phenomena. It showed that the hydrodynamic model with improved two-equation closure scheme could be successfully applied for the mesoscale analysis and prediction of ABL parameters.