Operating principles of frequency-modulated continuous-wave (FMCW) radar are reviewed, and their measurement limitations for atmospheric targets are discussed. In particular, we outline misregistration errors due to Doppler velocities and target coherence limitations on range resolution. The latter is of importance to volumetric scattering from atmospheric targets. Parallax errors and near-field operation are also considered. A high-resolution S-band FMCW radar developed at the University of Massachusetts is then described, and observations obtained by this system during the 1999 Cooperative Atmosphere-Surface Exchange Study are used to illustrate system performance. In the convective boundary layer, Rayleigh scatterers appear to dominate the observed vertical profile of mean reflectivity at S-band.