L originates in a homogeneous ocean (Gordon and McCluney, 1975). Since 



W 



K, depends on wavelength, <C> should as well; however, direct computation 

 (Clark, 1981) of <C > from the data acquired at the locations in Figure 

 B-l show that <C> is the same in all the visible CZCS spectral bands. 

 Furthermore, these computations show that there is no statistical 

 difference between <C> and the surface phytoplankton pigment 

 concentration. This indicates no significant variation of C within z qn , 

 suggesting that Zg Q was usually above the depth of the mixed layer. In 

 all of the bio-optical algorithms discussed here, <C> was evaluated at 

 520 nm. 



Morel and Priuer (1977) have optically classified sea water according 



the constituents chiefly responsible for determining their optical 



properties. Those waters for which phytoplankton and their covarying 



detrital material play the dominant role in determining the optical 



properties are called Case 1 waters, while those for which inorganic 



suspended material (such as that which might be resuspended from the 



bottom in shallow areas), which do not covary with phytoplankton, play 



an important role are referred to as Case 2 waters. Most of the open 



ocean waters are near Case 1. These waters are the easiest to treat 



from a remote sensing point of view. Figure B-3 shows the relationship 



between R(13) = < L (443)>/<L (550)> and the pigment concentration <C> 



for the waters in Figure B-l believed to qualify as Case 1, while 



Figure B-4 gives the same quantities using the data from all of the 



Figure B-l locations. The lines on these figures are linear regressions 



on data. Note the significantly tighter fit for the Case 1 waters, 



3 

 especially for <C > >1 mg/m . 



At high pigment concentration, <L(443)> usually becomes too small to be 

 retrieved from L t (443) with sufficient accuracy to be useful. In this 



case it is necessary to employ the ration R(23) = <L (520)>/<L (550 )> to 



w w 



extract the pigment concentration. This ratio and the associated 



3 

 regression for all of the data (Case 1 and Case 2) with C >_ 1.5 mg/m is 



shown in Figure B-5. R(23) is less sensitive than R(13) to variations 



in <C>. Both the ratios R(13) and R(23) (but derived from a much 



smaller data base) were used in processing the imagery presented by 



Gordon et al. (1980) yielding two pigment displays for each scene: one 



B-6 



