Chaotic Lagrangian Motion and Heat Transport in a Steady, Baroclinic Annulus Wave

Abstract

Lagrangian motion in a steady, baroclinic annulus wave is investigated numerically by following a tracer particle trajectory for a long period. Even for the regular Eulerian flow field of steady waves, the trajectory shows a chaotic nature, which is an example of “Lagrangian turbulence”. However, the chaotic trajectory has some organized structures depending on its position in the annulus. Based on the structure, the annulus of fluid is divided into the following regions: the upper-level and lower-level jets, the cyclonically and anticyclonically trapped regions, and the inner, outer and lower boundary layers. Some isolated regions in which the marked particle has never stayed for that period are also found inside the cyclonically trapped region and around the anticyclonically trapped region. Statistics over the long period show a preferred cyclic route of the region transitions: the outer boundary layer→the upper-level jet→the inner boundary layer→the lower-level jet or the lower boundary layer→the outer boundary layer. The number of dwell periods of the particle in the trapped regions is much smaller than that in the cyclic route, but the average time of one stay in the trapped regions is longer.
A Lagrangian view of the heat transport in the steady annulus wave is obtained: The fluid particle absorbs a large amount of heat in the outer boundary layer and releases it in the inner boundary layer, while it nearly conserves its temperature in the interior regions. Inward heat transport is small in every one cycle of the meander of the jets.