Eddy transport

Abstract

To study transport in the atmosphere, we normally use temporally and spatially averaged quantities associated with waves or disturbances. For instance, meridional transports of the general circulation of the atmosphere are described with the zonal average along a latitudinal circle. In general, the characteristics of mean transport depend on the averaging procedure. A spatial mean along one direction is called the Eulerian mean, while a mean over a set of fluid parcels is called the Lagrangian mean. For purely wavy oscillating disturbances, for instance, the positive and negative phases are canceled out to zero by the Eulerian mean regardless of its amplitude. For the Lagrangian mean, however, the mean position of fluid parcels generally has a motion, and net transport of energy or momentum occurs if the amplitude is finite. This concept is connected to formulation of the generalized Lagrangian mean.