Evaluation of Optical Proxies for Suspended Particulate Mass in Stratified Waters

Abstract

AbstractOptical instruments that measure the particulate beam attenuation and backscattering coefficients have been used widely to estimate suspended particulate mass (SPM) in various environments. In pycnoclines, density differences can cause significant forward light scattering (schlieren). This fluid-induced scattering increases the measured by instruments with small acceptance angles that are open to the environment (not pumped). When the 1-m bin-averaged buoyancy frequency (N) exceeds 0.05 s?1 in the Columbia River estuary, inaccurate estimates of are observed by such instruments. The schlieren phenomena do not affect the and measured with a pumped transmissometer or a backscattering meter. It follows that to obtain a reliable proxy of SPM in a highly stratified environment, the use of either a backscattering sensor or a pumped transmissometer is required.