Large-Scale Eddies and the General Circulation of the Troposphere

This chapter describes the large-scale eddies and the general circulation of the troposphere. Analyses of observations and general circulation models are evolving rapidly and complementing each other as they focus on the most dynamically interesting budgets and statistics. In the case of solid body rotation, the eddy activity spreads more or less uniformly over the sphere. The mean flow is accelerated in the region in which the initial wave activity is large, while the compensating deceleration determined by the dissipation of wave activity occurs over a wide range of latitudes. The natural procedure for constructing the analogous neutralized state in a continuously stratified atmosphere is to satisfy the Charney-Stern criterion by destroying the temperature gradient at the surface and by destroying the potential vorticity gradient in a layer adjacent to the surface. Upstream of the vorticity centers the low-level equatorward flow of cold continental air and the poleward flow of moist subtropical air have a frontogenetic effect, increasing the low-level baroclinicity in the storm track. It is suggested that the developing cross-fertilization among theory, numerical general circulation modeling, and observational studies will result in rapid advances in understanding of the large-scale flow in the atmosphere.