Schemm, C. E., and F. B. Lipps, 1976: Some results from a simplified three-dimensional numerical model of atmospheric turbulence. Journal of the Atmospheric Sciences, 33 (6), 1021-1041.
Abstract: A simplified set of subgrid-scale transport equations is used to compute
the stresses in a three-dimensional model of thermal convection in the atmosphere.
Terms appearing in the full transport equations thought not to be essential
to the large-scale dynamics are discarded, leaving prognostic equations
to be solved for the subgrid-scale energy and the virtual potential temperature
variance only. Equations for the Reynolds stresses and the subgrid-scale
temperature-velocity correlations are considerably simplified and can be
solved algebraically. A scale analysis of the full transport equations is
offered as partial justification for the present approach in the case of
nearly isotropic turbulence.
The problem studied is that of a well-mixed layer bounded above by a region
of strong stable stratification. The present model gives a significant improvement
in the representation of the large-scale variables as compared with the
more conventional eddy viscosity approach. In three experiments testing
different variations of the modified transport equations, the horizontally
averaged subgrid-scale energy components are found to be interrelated in
much the same sense as their corresponding resolvable turbulence energy
components. Above the inversion the turbulence intensity is observed to
decline sharply. The temperature inversion is maintained as the thermal
boundary layer rises, and in each case a countergradient upward heat transport
by the subgrid-scale eddies is detected in the upper half of the well-mixed
layer. In contrast, the temperature gradient at the base of the stable layer
is smoothed out considerably in the eddy viscosity run.