Lm. Polvani et Ra. Plumb, ROSSBY-WAVE BREAKING, MICROBREAKING, FILAMENTATION, AND SECONDARY VORTEX FORMATION - THE DYNAMICS OF A PERTURBED VORTEX, Journal of the atmospheric sciences, 49(6), 1992, pp. 462-476
The behavior of an isolated vortex perturbed by topographically forced
Rossby waves is studied using the method of Contour Dynamics. For a s
ingle-contour vortex a distinct forcing threshold exists above which t
he wave breaks in a dynamically significant way, leading to a disrupti
on of the vortex. This breaking is distinguished from the process of w
eak filamentary breaking described by Dritschel and classified here as
microbreaking; the latter occurs in nondivergent flow even at very sm
all forcing amplitudes but does not affect the vortex in a substantial
manner. In cases with finite Rossby deformation radius (comparable wi
th the vortex radius) neither breaking nor microbreaking occurs below
the forcing threshold. In common with previous studies using high-reso
lution spectral models, the vortex is not diluted by intrusion of outs
ide air, except during remerger with a secondary vortex shed previousl
y from the main vortex during a breaking event. The kinematics of the
breaking process and of the vortex interior and the morphology of mate
rial ejected from the vortex are described. When the Rossby radius is
finite there is substantial mixing in the deep interior of the vortex,
even when the vortex is only mildly disturbed. Implications for the s
tratospheric polar vortex are discussed.