Topographic generation of mesoscale vortices in mixed-layer models

The fundamental assumptions underlying mesoscale mixed-layer models of the atmospheric boundary layer are that 1) the flow is hydrostatic, and 2) the Reynolds-averaged potential temperature and horizontal velocity are vertically well mixed. The only significant source of the vertical component of vorticity is the curl of the divergence of the Reynolds stress, which can generate quasi-stationary vortices downstream of three-dimensional topography in flow containing buoyancy gradients. We provide quantitative guidance about conditions sufficient for these vortices to form under the mixed-layer modeling assumptions. We caution that observations do not appear to support strongly the assumption that velocity is vertically well mixed in baroclinic, convective boundary layers. -from Authors