Tracer transport in the presence of steady zonal jets in a forced and viscous barotropic model

Abstract

Tracers released into a barotropic fluid which was not subject to the beta-effect were seen to disperse according to the classical laws given by G.I. Taylor in 1921. In the short-time limit, the average total displacement was proportional to the time since release, and in the long-time limit, to the square root of the time. Tracers released into a fluid which was anisotropic and contained steady zonal jets, exhibited an inhibition of meridional excursion. However, the length scale associated with the sudden turnover in the average meridional displacement curve was observed not to be the distance from the line of tracer release to any of these jets, which would be expected if the jets were to act as barriers to meridional transport. The waves carrying the Eulerian velocity field at a given latitude were found to move slower than the tracers at that latitude, resulting in a phase lag consistent with the time scale of the turnover. Therefore, since tracers traveled faster than the waves, they never remained in either an area of northerlies or southerlies long enough to displace as rapidly meridionally as they did zonally.