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

We compared the mean normalized water-leaving radiances ([L_W¯(λ)]_N) of two in-water optical profilers, a compact optical profiling system (C-OPS) and a HyperPro II Optical Profiler (HP2), with modeled [L_W¯(λ)]_N at five stations in Monterey Bay, California. Although C-OPS and HP2 [L_W¯(λ)]_Ns were mostly within one standard deviation, C-OPS and modeled [L_W¯(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 [L_W¯(λ)]_N differences between C-OPS and HP2 likely stems from fluctuating water mass's inherent optical properties, the 25% error in [L_W(λ)]_Ns processed from HP2 casts, compared to <1% for C-OPS, is also important.