The near-bottom effects can be directly monitored exclusively in the visible since the IR and microwave signals originate at the air-water interface. There are a number of studies dedicated to bottom reflectance and the underwater light field in the context of remote sensing ( Boss and Zaneveld, 2003, Mobley and Sundman, 2003 and Kopelevich et al., 2007, and others) but we failed

to find experimental evidence for the contribution of light, backscattered by resuspended sediments, to the distribution of radiance in large marine shallows, although sediment resuspension is frequent there and has attracted the attention of many researchers ( Demers et al., 1987, Arfi www.selleckchem.com/Akt.html OSI-906 in vitro et al., 1993, Booth et al., 2000 and Scheffer et al., 2003, and others). The aim of our study was to come to a tentative conclusion whether a consistent relationship exists between winds of diverse directions and the distribution of the water-leaving radiance in a shallow aquatic area extending for tens of kilometres and more. A further objective of this work was to find out whether the reflectance of the resuspended sediments could be strong enough to dominate the bottom reflectance. The sea surface layer takes only a few hours to adjust to abrupt changes in wind strength and direction, whereas satellite images are obtained once a day at best.

Considerable uncertainty Methane monooxygenase therefore exists concerning the wind field configuration that shapes the distribution of optically-significant seawater admixtures at the instant of flight of a satellite colour scanner. Plausible wind field inhomogeneity is another cause of possible misinterpretation of the relationship between wind conditions and radiance distributions in the satellite images when these are compared on an everyday basis. We have assumed that these difficulties can be at least partly

bypassed if we cluster the images of a shallow area by wind directions at the instants of the survey and use the mean radiance distribution of a cluster to find features characteristic of respective wind conditions. Presumably, the averaging of a well-populated cluster of radiance distributions will result in a mean radiance distribution whose features are more closely related to the respective wind direction thanks to the random nature of the above uncertainty. Our approach implies the use of the red radiance Lwnred at λ > 650 nm and the reference radiance Lwnref at wavelengths of the ‘transparency window’ (from about 470 nm in the open ocean to 560 nm and more in the least transparent waters ( Jerlov 1976)) as guides for distinguishing the effects of the backscattering of light from the resuspended bottom sediments and from the interface between the sea bed and the water thickness (bottom reflectance).