A rigorous view of the uncertainties in Sunstone PSICAM (Point Source Integrated Cavity Absorption Meter) measurements are investigated. Multiple sources of error can greatly influence the accuracy of PSICAM absorption measurements: measurement noise, spectrometer stability, light source stability, calibration and external verification of the standard are a few of the sources of errors that were investigated. Measurement noise can be reduced through repetitive measurements. Using more than 300 averages for each measurement provided repeatability of measurements with a mean absolute difference less than 0.001 m-1 across the visible spectra. Like with other tube and cuvette style absorption meters, bubbles are a potent contaminant when determining absorption. The stability of the spectrometer with time and temperature are explored. Non-linearity and wavelength registration are also considered in reducing errors. Light source stability and output with time are also presented. Due to its small size the PSICAM is used both in the lab and at sea. Accurate absorption values require calibration to be conducted to account for the reflectivity (𝜌) of the sphere. Currently nigrosine dye is used to measure the reflectivity and requires a priori knowledge of the absorption of the dye. An examination of the stability of nigrosine dye is conducted for both filtered and non-filtered dye. A solid standard is proposed to improve the determination of reflectivity in the sphere.
synthetic bio-optical dataset of inherent optical properties (IOPs) was created based on Chlorophyll concentrations
ranging between 0.01 and 30 mg m-3. Dissolved and particulate fractions of absorption were varied to account for the
natural ranges in values. The IOPs will then be used as inputs to a time-resolved Monte-Carlo radiative transfer model to
generate accurate lidar backscatter time history wave forms. Test experiments were performed to validate the model,
where the primary lidar geometry in the model matched an existing system developed at HBOI under NOAA-OAR
funding. The system uses blue and green pulsed laser sources (473 and 532 nm, respectively) and has two telescopes
arranged at a 10° offset (on and off axis) from one another. The field of view of the telescopes is set at 1°. Approaches
are being investigated to invert simulated and measured lidar results to derive input water column IOP properties.
Results are tested through application to lidar measurements collected in an experimental tank with known suspended
particle type and concentration.
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