Atmos. Chem. Phys. Discuss., 9, 16085-16129, 2009
www.atmos-chem-phys-discuss.net/9/16085/2009/
doi:10.5194/acpd-9-16085-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Advective mixing in a nondivergent barotropic hurricane model
B. Rutherford1, G. Dangelmayr1, J. Persing1, W. H. Schubert2, and M. T. Montgomery3
1Department of Mathematics, Colorado State University, Fort Collins, CO 80523-1874, USA
2Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371, USA
3Department of Meteorology, Naval Postgraduate School, Monterey, CA 93943-5114, USA

Abstract. This paper studies Lagrangian mixing in a two-dimensional barotropic model for hurricane-like vortices. Since such flows show high shearing in the radial direction, particle separation across shear-lines is diagnosed through a Lagrangian field, referred to as R-field, that measures trajectory separation orthogonal to the Lagrangian velocity. The shear-lines are identified with the level-contours of another Lagrangian field, referred to as S-field, that measures the average shear-strength along a trajectory. Other fields used for model diagnostics are the Lagrangian field of finite-time Lyapunov exponents (FTLE-field), the Eulerian Q-field, and the angular velocity field. Because of the high shearing, the FTLE-field is not a suitable indicator for advective mixing, and in particular does not exhibit clear ridges marking the location of finite-time stable and unstable manifolds. The FTLE-field is similar in structure to the radial derivative of the angular velocity. In contrast, distinct and persisting ridges and valleys can be clearly recognized in the R-field, and their propagation speed indicates that transport across shear-lines is caused by Rossby waves. A radial mixing rate derived from the R-field gives a time-dependent measure of flux across the shear-lines. On the other hand, a measured mixing rate across the shear-lines, which counts trajectory crossings, confirms the results from the R-field mixing rate, and shows high mixing in the eyewall region after the formation of a polygonal eyewall, which continues until the vortex breaks down.

Citation: Rutherford, B., Dangelmayr, G., Persing, J., Schubert, W. H., and Montgomery, M. T.: Advective mixing in a nondivergent barotropic hurricane model, Atmos. Chem. Phys. Discuss., 9, 16085-16129, doi:10.5194/acpd-9-16085-2009, 2009.
 
Search ACPD
Discussion Paper
    XML
    Citation
    Final Revised Paper
    Share