# Abstract

A performance evaluation of ocean color chlorophyll-*a* algorithms was conducted based on the *in situ* fluorescence chlorophyll concentration (*F*_{chl}) measured by a sensor on the buoy SiMCosta-SC01 in coastal waters of South Brazil. The operational algorithms are used in MODIS and VIIRS sensors to derive satellite chlorophyll concentration (*C*_{sat}). *F*_{chl} values were successfully corrected for nonphotochemical quenching (NPQ) by an interpolation of sunrise and sunset daily measurements. A laboratory-derived calibration coefficient was applied to convert the unquenching *F*_{chl} values into chlorophyll concentration (*C*_{flu}). Overall, linear regression analysis between *C*_{flu} and *C*_{sat} for both sensors showed good results, with the coefficient of determination (R^{2}) varying between 0.88 and 0.96, slopes between 0.92 and 1.02 and intercepts between -0.17 and 0.13. The MODIS algorithm (R^{2} = 0.96, slope = 1.02, RMSE = 0.16 mg m^{-3}, BIAS = 0.16 mg m^{-3}, for N = 222 and time interval ±1 h) presented slightly better performance than VIIRS (R^{2} = 0.92, slope = 0.96, RMSE = 0.25 mg m^{-3}, BIAS = -0.25 mg m^{-3}, for N = 284 and time interval ±1 h). These results represent the most comprehensive satellite data analysis for this region, suggesting that the approach may be applicable to other SiMCosta buoys.

**Descriptors:**

Ocean color; MODIS; VIIRS; Southern Brazilian Coastal Waters; *in situ* fluorescence chlorophyll-*a*; moored measurements