Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 10 2 2010 10.5194/acp-10-475-2010 http://www.atmos-chem-phys.net/10/475/2010/ http://www.atmos-chem-phys.net/10/475/2010/acp-10-475-2010.html http://www.atmos-chem-phys.net/10/475/2010/acp-10-475-2010.pdf 475 497 2010-01-20 Advective mixing in a nondivergent barotropic hurricane model B. Rutherford rutherfo@math.colostate.edu G. Dangelmayr J. Persing W. H. Schubert M. T. Montgomery Department of Mathematics, Colorado State University, Fort Collins, CO 80523-1874, USA Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371, USA Department of Meteorology, Naval Postgraduate School, Monterey, CA 93943-5114, USA 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 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. 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