Underwater polarization by scattering hydrosols

Abstract

During more than six decades of underwater polarization research, polarization by hydrosols has got little attention. It was somewhat neglected by both optical oceanographers and marine biologists, because Rayleigh (molecular, sub-micronic) scattering was generally assumed as the main process determining the polarization field in water, similarly to the one in the atmosphere. Recent measurements and modeling have shown that the Rayleigh assumption is inaccurate, and instead Mie scattering (i.e. scattering by particles suspended in water, such as plankton and minerals of microns in size) should be considered as the dominating process, even in clear waters. This chapter focuses on the physical processes that determine the polarization in water, and presents the theoretical basis of scattering and radiative transfer which is needed to investigate and solve the effect of scattering particles of varied sizes and shapes on polarization, and the methods in use to measure it in situ. The chapter also reviews past studies on underwater polarization modeling and measurements, emphasizes the missing knowledge in the topic, and thus encourages future research.