A method for tracking the Brownian motion to estimate the size distribution of submicron particles in seawater.

Because the diffusivity of particles undergoing the Brownian motion is inversely proportional to their sizes, the size distribution of submicron particles can be estimated by tracking their movement. This particle tracking analysis (PTA) has been applied in various fields, but mainly focused on resolving monodispersed particle populations and is rarely used for measuring oceanic particles that are naturally polydispersed. We demonstrated using Monte Carlo simulation that, in principle, PTA can be used to size natural, oceanic particles.

Shape of particle backscattering in the North Pacific Ocean: the χ factor.

Volume scattering functions were measured using two instruments in waters near the Ocean Station Papa (50°N 145°W) and show consistency in estimating the factor attributable to particles (). While in the study area exhibits a limited variability, it could vary significantly when compared with data obtained in various parts of the global oceans. The global comparison also confirms that the minimal variation of is at scattering angles near 120°.

Variability of relationship between the volume scattering function at 180° and the backscattering coefficient for aquatic particles.

Properly interpreting lidar (light detection and ranging) signal for characterizing particle distribution relies on a key parameter, (), which relates the particulate volume scattering function (VSF) at 180° (()) that a lidar measures to the particulate backscattering coefficient (). However, () has been seldom studied due to challenges in accurately measuring () and concurrently in the field. In this study, (), as well as its spectral dependence, was re-examined using the VSFs measured in situ at high angular resolution in a wide range of waters.

Calibration of the LISST-VSF to derive the volume scattering functions in clear waters.

The recently commercialized LISST-VSF instrument measures the volume scattering function (VSF) from 0.1° to 15° with a traditional laser diffraction unit (LISST) and from 15° to 155° with an eyeball component. Between these two optical components, only the LISST unit is calibrated.

Re-examining the effect of particle phase functions on the remote-sensing reflectance.

Even though it is well known that both the magnitude and detailed angular shape of scattering (phase function, PF), particularly in the backward angles, affect the color of the ocean, the current remote-sensing reflectance (R) models typically account for the effect of its magnitude only through the backscattering coefficient (b). Using 116 volume scattering function (VSF) measurements previously collected in three coastal waters around the U.S.