Convective eddy momentum tendencies in long cloud-resolving model simulations

The convective eddy momentum tendency F, neglected in many global circulation models, looks broadly similar in two- and three-dimensional simulations. It has a large component in quadrature with the mean wind profile, tending to cause momentum profile features to descend.

This component opposes, and exceeds in magnitude, the corresponding large-scale vertical advective tendency, which would tend to make features ascend in convecting regions. The portion of F in phase with the mean wind is isolated by vertically integrating F . u, yielding a kinetic energy tendency that is overwhelmingly negative. The variation of this energy damping with shear flow kinetic energy and convection intensity (measured by rain rate) gives a cumulus friction'' coefficient around -40% to -80% per centimeter of rain in 3D runs.