Simulated performance of remote sensing ocean colour algorithms during the 1996 PRIME cruise

Coincident pigment and underwater radiometric data were collected during a cruise along the 20°W meridian from 60°N to 37°N in the north-eastern Atlantic Ocean as part of the Natural Environment Research Council (NERC) thematic programme: plankton reactivity in the marine environment (PRIME). These data were used to simulate the retrieval of two bio-optical variables from remotelysensed measurements of ocean colour (for example by the NASA Sea-viewing wide field-of-view sensor, SeaWiFS), using two-band semi-empirical algorithms. The variables considered were the diffuse attenuation coefficient at 490 nm, (Kd(490), units: m−1) and the phytoplankton pigment concentration expressed as optically-weighted chlorophyll-a concentration [Ca, units: mg m−3]. There was good agreement between the measured and the retrieved bio-optical values. Algorithms based on the PRIME data were generated to compare the performance of local algorithms (algorithms which apply to a restricted area and/or season) with global algorithms (algorithms developed on data from a wide variety of water masses). The use of local algorithms improved the average accuracy, but not the precision, of the retrievals: errors were still ±36% (Kd) and ±117% (Ca) using local algorithms.