normalized DR curves should be classified : 1) The concentration 
of optically active substances is negligible, the water is nearly 
pure - in the range 420 * 700 nm the DR values decrease monoto- 
nously with the increase of A (curve 1 in Fig.2a); 2) medium con- 
centrations of all the three admixtures under consideration - cha- 
racteristic minimum of the DR curve near 440 nm appears (according 
to the maximum of the spectral curve of the chlorophyll absorption 
coefficient), the maximum of the DR curve lies near 520 nm (curve 
2 in Fig. 2b); 3) heavily turbid water - the minima at 440 nm are 
flattened, the maximum of the DR curve is shifted to longer 
wavelenaths (curve l and 2 in Fig.2c). Thus, the high concentration 
of other optically active matters ( high concentration of yellow 
substance only is sufficient enough) conceal the variations of 
chlorophyll concentration in the DR spectral curves. 
It should be marked that similar to above mentioned patterns 
of the DR spectral curves (or the spectral curves of sea surface 
brightness) are obtained experimentally by many authors (Clarke 
et al: (1970), Maul and Gordon (1975) , Konovalov (1979), Eerme and 
Lokk (1978), Arst and Tokk (1981), Lokk and Purga (1982)). 
As shown by some investigators (see, e.g., Smetacek (1980)), 
a correlation exists between the concentrations of Chlorophyll and 
other optically active substances in the sea. Therefore, we have 
computed the DR spectra assuming that cH - Cc = Cy in the following 
two cases: 1) the vertical profiles of these concentrations corres- 
pond to those in/Fig.1; 2) CH = ce = Sy > ©(z = 0) for all depths, 
whereas the values of c(z = 0) are taken equal to those in Fig.l. 
As a result, we have two groups of DR values, that help us to answer 
to the questions:" How much do the DR spectra near the sea sur- 
face depend on the intensity and location of the maximum concen- 
tration of optically active substances in the water and how much 
do they depend on the subsurface concentration of those substances?" 
The results of these computations are given in Table 1. 
  
  
  
: ‚Table 1 
Normalized to 520 nm values of the diffuse reflectance of 
the sea just below the water surface bv assumption that cy = ce= Cy 
Profile of admixtures cf cz = 0) 
A. (nm) T II AA IE IV Wlra IVa/l]lcz3.2  |czl.6 c=1.0 
400 0.43 0.52 0.63 0.65 0.48 0.63 0.44 0.55 0.63 
420 0. 37 0.45 0.56 0.57 0.41 0.56 0.38 0.48 0.58 
440 0.32 0.39 0.49 0.50 0.36 0.49 0.33 0.42 0.51 
460 0.42 0.50 0.62 0.63 0.46 0.62 0.43 0.54 0.65 
480 0.50 0.58 0.73 0.73 0.54 0.72 0.51 0.63 0.76 
500 0.80 0.85 0.95 0.97 0.81 0.96 0.80 0.91 0.99 
520 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 
540 1.03 0.98 0.90 0.89 1.03 0.90 1.03 0.94 0.88 
560 0.95 0.86 0:73:59 £71 0.94 0.72 0.93 0:79 0.71 
580 0.78 0.64 0.50 0.50 0.72 0.50 0.74 0.58 0.50 
600 0.52 0.37 0.28 0.28 0.44 0.29 0.48 0.35 0.29 
620 0.41 0.27 0.21 0.21 0.33 0.22 0.38 0.27 0.22 
640 0.36 0.23 0.18 0.18 0.29 0.18 0.33 0.23 0.19 
660 0.29 0.21 0.15 0.15 0.23 0.15 0.28 0.19 0.16 
680 0.22 0.16 0.12 0.12 0.18 0.12 0.21 0.15 0.12 
700 0.22 0.15 0.11 0.11 0.18 0.11 0.21 0.14 0.12 
  
  
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