The Mean-Meridional Transport Circulation of the Troposphere in an Idealized GCM

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Abstract
Large numbers of particle trajectories are used to characterize the mean-meridional transport circulation of an idealized general circulation model (GCM). The GCM has a uniform land surface, no topography or land–sea contrasts, and no seasonal cycle. The trajectories are analyzed using both Lagrangian-mean statistics and an approach based on the Green's function of the tracer transport equation. It is shown that the distribution of particle trajectories provides an estimate of the ensemble-mean Green's function for the inviscid transport equation. Lagrangian means have a number of problems that render their interpretation difficult, including boundary effects and selection of the appropriate averaging period. The Green's function, on the other hand, provides a quantitative description of the transport circulation that is easy to visualize and interpret. The results demonstrate that within the idealized model the atmosphere can be divided into three parts: the Southern Hemisphere extratropics, the... Abstract Large numbers of particle trajectories are used to characterize the mean-meridional transport circulation of an idealized general circulation model (GCM). The GCM has a uniform land surface, no topography or land–sea contrasts, and no seasonal cycle. The trajectories are analyzed using both Lagrangian-mean statistics and an approach based on the Green's function of the tracer transport equation. It is shown that the distribution of particle trajectories provides an estimate of the ensemble-mean Green's function for the inviscid transport equation. Lagrangian means have a number of problems that render their interpretation difficult, including boundary effects and selection of the appropriate averaging period. The Green's function, on the other hand, provides a quantitative description of the transport circulation that is easy to visualize and interpret. The results demonstrate that within the idealized model the atmosphere can be divided into three parts: the Southern Hemisphere extratropics, the...