An idealization for the atmospheric boundary layer that assumes uniform (well mixed) values with height within the boundary layer, capped by a discontinuity (or jump) at the top of the boundary layer. Another name for this approach is a slab model because the uniform part of the boundary layer behaves in a similar way to a uniform slab of material. Such jump or step models are reasonable simplifications for the convective boundary layer when vigorous thermals tend to keep the boundary layer well mixed, but are poor idealizations for statically stable and neutral boundary layers.