We investigate the structure and maintenance of barotropic jets which naturally arise in a forced-dissipative model of baroclinic turbulence. The model we use is a three-dimensional quasi-geostrophic model on a beta-plane with radiative relaxation forcing and Ekman friction dissipation. The nature of the jets is diagnosed in a number of ways, principally by examining the potential vorticity structure of the flow, and by calculating the transport in terms of Nakamura's effective diffusivity diagnostic. The results show that the jets act as barriers to transport, restricting the degree of North-South mixing, only in the upper part of the domain. In the lower part of the domain the baroclinic activity is sufficiently strong to mix across the entire domain, so no barrier forms. This dichotomous vertical structure is strongly reminiscent of the mid-latitude lower atmosphere, with the tropopause acting as a barrier to transport only at the upper limit of the baroclinically active region (the troposphere).
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12th Conference on Atmospheric and Oceanic Fluid Dynamics