Lifting by Convergence Lines

Abstract The lifting depth of a convergence line in an unstratified boundary layer beneath a stably stratified atmosphere is examined with both analytical and numerical models. Cases are considered with and without flow in the layer above the convergence line. Three different stability profiles above the boundary layer are also considered: an inversion, continuous stratification, and a combination of the two. For the case in which there is no flow above the convergence line, analytical solutions are obtained for the lifting depth for the three different stability profiles. Simulations of the flow with a nonlinear, nonhydrostatic model show good agreement with these analytical predictions. The presence of flow in the upper layer increases the complexity of the problem due to the presence of gravity waves in the steady-state solution. For an atmosphere with just an inversion, the analytical model predicts that, for hydrostatic flow, the depth of lifting is independent of the upper-level flow; while for nonh...