The determination of in-water spectral irradiance and the subsequent estimation of ocean optical properties is essential for the meaningful understanding and predictive modeling of the marine photoenvironment; this in turn is fundamental to the understanding of both biological and physical oceanographic processes. Further, the accurate estimation of near-surface optical properties is essential for the surface validation of ocean color satellite sensors. Two primary sources of error in the determination of optical properties at sea are the perturbation of the in-water radiant energy field due to the ship (Gordon, 1985; Smith and Baker, 1986) and the estimation of quantitative corrections for atmospheric variability in radiant energy incident on the sea-surface during in-water measurements (Smith and Baker, 1984). Here we briefly describe two new optical oceanographic instrument and deployment techniques designed to reduce or eliminate these sources of error. The first is an Optical Free Fall Instrument (OFFI) designed to profile the water colunm away from potential perturbation effects of the ship: the second is an Optical Surface Floating Instrument (OSFI) designed to obtain continuous optical data just below the air-water interface. A cartoon illustrating deployment of these instruments is shown in Fig. 1.

Waters, K.J., R.C. Smith, and M.R. Lewis. 1990. Avoiding ship-induced light-field perturbation in the determination of oceanic optical properties. Oceanography 3(2):18–21, https://doi.org/10.5670/oceanog.1990.03.

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