Turbulent flow in two and three dimensions.

Abstract

Three-dimensional turbulence occurs mainly in convective clouds and in the atmospheric boundary layer. Two-dimensional turbulence is a model for the statistical features of large-scale flows in the atmosphere. The differences between two- and three-dimensional turbulence are discussed, with a minimum of mathematics, in terms of elementary vorticity dynamics. The influence of the microstructure on the evolution of the large-scale features of the flow field is explored in some detail. A simple rationale is given for ignoring subgrid scale fluxes in numerical weather prediction. (A)