A type of wind profiler specially designed to study the lower part of the troposphere. Because clear-air reflectivities in the boundary layer are usually orders of magnitude higher than in the upper troposphere, these profilers can be smaller, lower powered, and less expensive than those profilers designed to cover higher regions of the atmosphere (see, e.g.,, MST radars). Boundary layer radars are generally characterized by short pulse lengths (less than 100 m) and the ability to make measurements starting at 100–200 m above the radar and extending to at least 2–4 km under typical atmospheric conditions. To satisfy these requirements, boundary layer radars usually operate in the UHF radar band.