Phytoplankton pigment concentrations in the Middle Atlantic Bight: comparison of ship determinations and CZCS estimates

TLDR

The study develops and details algorithms that translate Nimbus‑7 Coastal‑Zone Color Scanner ocean color observations into phytoplankton pigment concentrations, primarily chlorophyll‑a. These algorithms are applied to four Nimbus‑7 images of the Middle Atlantic Bight and Sargasso Sea, comparing retrieved pigment concentrations to ship‑based measurements, using an atmospheric correction that requires no surface data. The retrieved pigment concentrations exhibit 30–40 % error over 0.08–1.5 mg m⁻³, while the atmospheric correction achieves about 10 % error in water‑leaving radiance.

Abstract

The processing algorithms used for relating the apparent color of the ocean observed with the Coastal-Zone Color Scanner on Nimbus-7 to the concentration of phytoplankton pigments (principally the pigment responsible for photosynthesis, chlorophyll a) are developed and discussed in detail. These algorithms are applied to the shelf and slope waters of the Middle Atlantic Bight and also to Sargasso Sea waters. In all, four images are examined, and the resulting pigment concentrations are compared to continuous measurements made along ship tracks. The results suggest that over the 0.08-1.5-mg/m3 range the error in the retrieved pigment concentration is of the order of 30-40% for a variety of atmospheric turbidities. In three direct comparisons between ship-measured and satellite-retrieved values of the water-leaving radiance the atmospheric correction algorithm retrieved the water-leaving radiance with an average error of approximately 10%. This atmospheric correction algorithm does not require any surface measurements for its application.