In comparison with the previous issue , the modified algorithms for calculation of chlorophyll and suspended matter concentrations were used. They were derived by using new in situ data obtained in the summer expeditions of 2008-2009 in the northern part of the Caspian Sea .
The regression equation for calculation of chlorophyll concentration from SeaWiFS data is similar to the previous one :
Chl = 0.732·[Lwn(555)/Lwn(510)]3.40, (15)
where Lwn(555) and Lwn(510)] are the normalized water-leaving radiances at 555 and 510 nm (n = 55, r2 = 0.708, the error is equal to 0.33 mg/m3).
The algorithm to derive chlorophyll concentration from MODIS-Aqua data was simplified in comparison with :
Chl = 0.573 (Rrs(488)/Rrs(551)-2.39. (16)
where Rrs(488) and Rrs(547) are the above-surface remote-sensing reflectance at 488 and 547nm, respectively (n = 55, r2 = 0.638, the error is equal to 0.41 mg/m3).
Particle backscattering and TSM
First, the particle backscattering coefficient bbp was derived from the remote sensing reflectance corrected to the bottom reflection . TSM concentration was calculated by using the regression equation between TSM and the particle backscattering coefficient bbp :
TSM = 67.1 bbp + 0.554, (17)
where TSM is in mg/l , bbp in m-1 (n=42, R2 = 0.835, the regression error is 0.81 mg/l).
Yellow substance absorption
The values of ag were calculated with the semi-analytic algorithm as described in 4.2. The algorithm worked stably only for the May-September period so the mean monthly distributions of the ag values were calculated only for this season.