The Backscattering Enigma in Natural Waters

One of the fundamental problems in ocean optics over the past several decades has been understanding the source of backscattering in the ocean. Because of experimental limitations and the limitations in available theoretical models, our knowledge of the causative agents for backscattering remains poor. Experimentally, we have been limited by a lack of scattering sensor instrumentation and a methodology for routine measurement of the submicron particle size distribution. Theoretically, most models have used Mie theory with the hope that natural particles of complex shape and structure can be approximated well by homogeneous spheres. For the Navy, poorly parameterized backscattering greatly compromises applications that involve the interpretation of passive remote sensing or lidar. This is particularly true in coastal regions where current inversion models break down because the effects of changing particle composition are not adequately understood. Our long term goal is to better understand the source of backscattering in natural waters.