Comparison of two in-water optical profilers in a dynamic coastal marine ecosystem.

ABSTRACT

We compared the mean normalized water-leaving radiances ([LW¯(λ)]N) of two in-water optical profilers, a compact optical profiling system (C-OPS) and a HyperPro II Optical Profiler (HP2), with modeled [LW¯(λ)]N at five stations in Monterey Bay, California. Although C-OPS and HP2 [LW¯(λ)]Ns were mostly within one standard deviation, C-OPS and modeled [LW¯(λ)]N showed the lowest absolute percent differences (≤25% for most wavelengths) at four of the stations. We attribute this to C-OPS's high vertical resolution (∼1 cm), which is important for detecting changes in optical layers and for measuring the upper 0-0.5 m of the water column. HP2's low vertical resolution (∼50 cm), low signal-to-noise ratio, and inability to measure the upper 0-0.5 m are problematic in Monterey Bay. Although a significant component of the [LW¯(λ)]N differences between C-OPS and HP2 likely stems from fluctuating water mass's inherent optical properties, the 25% error in [LW(λ)]Ns processed from HP2 casts, compared to <1% for C-OPS, is also important.