Stratified Turbulence in the Atmospheric Mesoscales

The first author proposed earlier that the atmospheric energy spectrum in the mesoscale range is controlled by upscale energy transport in stratified and geostrophic turbulence, with the source of the energy probably convective clouds and storms. This hypothesis is reviewed in the light of a variety of theoretical and mechanistic tests, mostly involving numerical simulation. Some conflicting results are noted, with fluid dynamics simulations mostly negative and meteorological simulations positive, including one new set presented here. The rapid increase in larger-scale energy shown in our simulations should, however, be ascribed in part to a different mechanism, involving the rapid growth of the unconstrained outflow and its further spreading by mean shear. Received 23 May 1997 and accepted 21 February 1998