Comparison of SeaWiFS bio-optical chlorophyll-a algorithms within the OMEXII programme

Optical profiles taken aboard the Belgica 98/15 cruise during the Iberian upwelling season were applied to five empirical and two semi-analytical models from the literature and the results compared to in situ HPLC chlorophyll-a (chla) concentrations. When applied to the limited Belgica data set the Carder et al. (1999) model gave the most accurate semi-analytical and the Kahru and Mitchell ( 1999) algorithm the most accurate empirical estimates of chla. When the current SeaWiFS processing algorithm (OC4) and Carder semi-analytical approaches were applied to SeaWiFS data and compared with in situ pigment measurements, the Carder algorithm was shown to give closer agreement with in situ values at both high (> 1 mg m(-3)) and low (< 1 mg m(-3)) chla concentrations. This contrasts with the current SeaWiFS algorithms which typically under (over) estimate high ( low) chla. As the Carder model is computationally fast it should be used in routine processing of SeaWiFS data.