Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2018, Vol. 15, No. 2, pp. 183-190
On the mesoscale structure of the Black Sea satellite images during coccolithophorid bloom
1 P.P. Shirshov Institute of Oceanology RAS, Moscow, Russia
Accepted: 21.12.2017
DOI: 10.21046/2070-7401-2018-15-2-183-190
The work is devoted to the effect of blooms of coccolithophores on the mesoscale variability of the spectral reflectance Rrs in the Black Sea offshore. The indicator of spatial variability was the autocorrelation function (ACF). Two images of the testing site in the Black Sea served as a matter for enquiry. They exhibited equally acceptable quality, corresponded to early and mature age of the bloom in 2006, and were obtained with the MERIS sensor at GSD = 300 m. After averaging over 1×1 km cells, these data were used for mapping Rrs(560) over the testing site and computing the ACF of distributions of Rrs at λ = 443, 510, 560, 681 nm and CHL (content of chlorophyll a in water found with the universal MERIS-algorithm) in seven meridional sections within the testing sites. A trend common to all characteristics is established: bloom intensification is accompanied by simplification and unification of the form of ACF in such a way that they become indistinguishable from ACF for Rrs(681). This fact and specific optical properties of the Black Sea waters allow you to admit that the layer of water-leaving radiance origination cannot be more that 2 m thick regardless of wavelength as soon as a threshold intensity of blooming is reached. Conceivably, in this case the backscattering of solar radiation by the coccolithophoric calcite suspension becomes so significant that contributions of other factors of water-leaving radiance origination are negligible. If so, simplification and unification of the ACF of quantities retrieved from spectral reflectance may be inherent to coccolithophores blooms of the highest intensity in any oceanological province.
Keywords: reflectance, mesoscale inhomogeneities, autocorrelation function, remote sensing, MERIS, Black Sea, coccolithophore bloom
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