## 3 OOB Effect Evaluation  
The result for the Case 1 water is shown in Table 2. Generally speaking, the larger OOB values (\(\geq\)2%, shown as bold numbers) were mainly found in the oligotrophic waters (with low Chla) and at longer bands, where the water-leaving signals were weak; a clear decreasing trend of OOB for the three bands exists with elevated Chla (except the green band in eutrophic waters). Specifically, among the three visible bands, the blue band showed the lowest OOB, with no more than \(-\)1% for both cameras, and the OOB effect can be neglected accordingly, at least for the concerned Chla range of 0.01 mg/m\({}^{3}\)-10 mg/m\({}^{3}\). The OOB in the red band ranged from \(\sim\)2% to \(\sim\)20% \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Nominal Central**} & \multicolumn{2}{c}{**Band Interval with 50\%**} & \multicolumn{2}{c}{**Band Interval with 1\%**} \\  & & **Wavelength/nm** & **Response/nm** & **Response/nm** \\ \hline \multirow{4}{*}{**Camera 1**} & B1 & 461.5 & 423–500 (77) & 415–505 (90) \\  & B2 & 557.5 & 518–597 (79) & **464–608(144)** \\  & B3 & 651.0 & 610–692 (82) & 604–700 (96) \\  & B4 & 823.0 & 759–887(128) & 750–902(152) \\ \hline \multirow{4}{*}{**Camera 2**} & B1 & 461.5 & 423–500 (77) & 415–505 (90) \\  & B2 & 558.0 & 518–598 (80) & **511**–608 (**97**) \\  & B3 & 649.5 & 609–690 (81) & 602–700 (98) \\ \cline{1-1}  & B4 & 825.5 & 761–890(129) & 750–905(155) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Band specifications for the two cameras of HY-IC CZI. The nominal center wavelengths (defined as the center of the 50% peak response) and band intervals with 50% (1%) peak response are determined from the spectral response functions. The specifications for the two cameras are found to be almost identical with exceptions in the green band, shown as bold numbers. for both cameras, which resulted from the low level of water-leaving radiance in the clear waters. It was also noted that in the blue and red bands, the two CZI cameras had almost the identical OOB response characteristics. For the green band, the OOB of the two cameras showed some differences, which were in the range of \(-\)0.9%\(\sim\)4.6% and \(-\)1.1%\(\sim\)12.8%, respectively. Their major discrepancy (4%\(\sim\)8%) was found in the oligotrophic waters (with Chla of 0.01 mg/m\({}^{3}\)\(\sim\)0.1 mg/m\({}^{3}\)). In addition, on the whole for the waters with Chla less than \(\sim\)0.1 mg/m\({}^{3}\), the OOB effect cannot be neglected, and needs to be accounted for properly. As an example, Figure 4 shows the satellite derived global Chla distribution [23] from which it is clear that the waters with Chla \(\leq\) 0.1 mg/m\({}^{3}\) were mainly located in the sub-tropic gyres of the Pacific, Atlantic, and Indian Oceans, far from the coast which is the hotspot of CZI observation. The central wavelength shifts of the blue, green, and red bands for Camera 1 (Camera 2) are in the range of \(-\)4.5-13.5 nm (\(-\)2.5\(\sim\)13.5 nm), \(-\)8.5-20.5 nm (\(-\)9.5\(\sim\)19.5 nm), \(-\)20\(\sim\)\(-\)24 nm (\(-\)18.5\(\sim\)\(-\)21.5 nm), respectively, with Chla ranging from 0.01 mg/m\({}^{3}\) to 10 mg/m\({}^{3}\). Figure 4: Annual average of the global chlorophyll a concentration distribution in 2010, which was merged from AQUA MODIS (Moderate-resolution imaging spectra-radiometer), ENVISAT MERIS (Medium-spectral Resolution Imaging Spectrometer), and FY-3 MERSI (Medium Resolution Spectral Imager) [23]. The areas in dark blue are characterized by low Chla (\(\leq\)0.1 mg/m\({}^{3}\)), where the noticeable OOB (out-of-band) effect (\(\geq\)2%) in the CZI green band need be corrected.