A method for obtaining particle size spectra from vertical profiles of scattering strength in planetary boundary layers is presented. It is assumed that the boundary layer is horizontally homogeneous, and that the vertical turbulent diffusion of particles can be modeled from a knowledge of the surface friction velocity. Equilibrium boundary layer profiles for each class of suspended particles are assumed to be established resulting from the balance between vertical turbulent diffusion and gravitational settling. The forward problem thus models the depth-dependent scattering as the sum across size classes weighted by number density and scattering cross-section in accordance with established scattering theory. Constrained inverses produce the size spectra. Results of inversions from synthetic ocean data are presented for optical transmissometry and acoustic backscattering. Inversions of acoustic field data from the HEBBLE experiment are also presented. Finally, the applications of the work presented for the design of ocean boundary layer experiments, its application in other fields, and the directions for future research are discussed.