Ross, B. B., and I. Orlanski, 1982: The evolution of an observed cold front. Part I: Numerical simulation. Journal of the Atmospheric Sciences, 39 (3), 296-327.
Abstract: The 48 h evolution of an observed cold front is simulated by a three-dimensional
mesoscale-numerical model for a typical springtime synoptic situation over
the southeastern United States. The model used in this study employs anelastic
equations of motion on a limited-area domain with locally determined inflow/outflow
side boundaries.
Both the observed and simulated characteristics of the weather system indicate
a mature front which intensifies and then weakens over the 48 h period.
Moist convection occurs in the form of intermittent squall lines in the
observed case; in the numerical simulation, convection develops above and
somewhat ahead of the surface front after 24 h as an ensemble of convective
cells.
An investigation is made of the mesoscale and subsynoptic-scale features
of this solution to determine their sensitivity to the inclusion of moisture
and to the magnitude of the eddy viscosity used in the numerical simulation.
The primary effect of increased eddy viscosity is to reduce somewhat the
propagation speed of the front. The major changes due to moisture inclusion
occur when convection develops along the cold front; these convective effects,
which are apparent in the subsynoptic as well as the mesoscale features
of the solution, include increased low-level convergence, reduced surface
pressure due to diabatic heating, and the deflection of winds due to upper-level
divergence. In addition, small temperature changes occur in the middle troposphere
between the jet stream and the surface front when either viscosity or moisture
is varied; these disturbances are a clear manifestation of the effect which
changes in the cross-stream circulation intensity have upon the frontal
system.
A fundamental feature of the mesoscale structure of the front in all cases
is the tendency of the line of maximum horizontal convergence at the surface
to move ahead of the line of maximum vertical vorticity. This phase shift
appears to be related to the propagation characteristics of the frontal
system. Also, the mesoscale moist convection develops a cellular structure
throughout the convective zone in the low-viscosity solution; the use of
higher viscosity tends to suppress these cells, particularly near the surface.