In the ocean, degradation products of chlorophyll a, the phaeopiqments, 

 are also present. These are produced upon acidification of chloroDhyll a 

 as would happen for example in the gut of zooplankton feedinq on Dhyto- 

 plankton. The phaeopiqments have absorption characteristics which are so 

 similar to chlorophyll a in the blue that seperation of these piqments with 

 an instrument with as few spectral bands as the CZCS is impossible. 

 Therefore, for CZCS studies it is necessary to consider chlorophyll a and 

 the phaeopigments together. The sum of the concentrations of chlorophyll a^ 

 and the phaeopigments will henceforth be called the phytoplankton piqment 

 concentration or just the pigment concentration and will be denoted by C. 



To establish algorithms for retrieval of the pigment concentration from 

 CZCS imagery a field program was initiated by NOAA/NESS in 1975. This 

 program consisted of measurements of vertical profiles of uowelled 

 (traveling toward the zenith) spectral radiance (L ) and piqment concen- 

 tration along with other optical, physical, and biological Darameters of 

 importance for the interpretation of ocean color remote sensing data 

 (Gordon and Clark, 1980a; Clark et al., 1980; Clark, 1980). These 

 measure-ments were made at the over 60 locations shown in Figure B-l. 

 The measurements of chlorophyll a and its associated phaeopigments were 

 made f luorometrically using the technique described by Yentsch and 

 Menzel (1963) with the modifications given by Holm-Hansen et al. (1965). 

 The upwelled spectral radiance measurements were made at 5 nm increments 

 with a submersible radiometer covering a spectral range from 400 to 700 

 nm. The spectral resolution of the instrument was 4 nm. 



From profiles of L ( x,z), where z is depth, the attenuation coefficient 

 of upwelled spectral radiance K (A) defined by 



K u (x) = - d Ln(L u (A,z)) /dz (2) 



was computed. This allowed determination of the upwelled spectral radi- 

 ance just beneath the surface L (x,0) from 



L u (x,0) = L u (A, z )exp +K u (Mz • 0) 



B-2 



