Hence, at sites with more than 3 m of water, the bottom reflectance contributes nothing to Lwnred although the latter remains sensitive to resuspended bottom sediments penetrating the near-surface layer. In other words, the 3 m depth is a universal threshold of red radiance sensitivity to bottom reflection ( Figure 1), and the similarity of the horizontal distributions of Lwnred and Lwnref over the shallow area points to a particularly strong resuspension GW 572016 of bottom sediments, because Zor for Lwnref delimits a much thicker surface layer than Zor

for Lwnred does (Lwnref /Lwnred criterion). We chose a shallow in the south-eastern Caspian Sea as the study area (Figure 2) because it has the features of a desired natural model: (1) the waters of the South Caspian basin, flowing across the shallow, are fairly transparent (Simonov & Altman 1992), which facilitates observations of resuspension effects; (2) the bed of the shallow is mainly free of sea grass and consists of bare sand, silt and other light-coloured sediments that are detachable from the sea floor by quite moderate water motions; (3) digital bottom topography of the Caspian

Sea is available online at http://caspi.ru/HTML/025/02/Caspy-30-10.zip (Figure 2b); (4) the shallow extends for about 200 km in latitude and from 40–50 to 110–120 km in longitude and is clearly delimited Pictilisib purchase by the shore line in the east and by an underwater precipice to the west of the 20–30 m depth contours (Figure 2b); (5) only a few rivers with a minor discharge rate enter the south-eastern Caspian Sea, which minimizes the occurrence of externally supplied sediments; (6) the bottom relief is fairly smooth at sites of plausible sediment resuspension (depth range up to 15–20 m, Figure 2b); (7) the south-eastern Caspian Sea is a region where sunny weather prevails. Our approach implies the use of a long-term data set of the Sea-viewing Wide Field-of-view Sensor of (SeaWiFS), since it is equipped with a sun-glint avoidance facility. Use has been made of archived water-leaving radiance distributions at wavelengths 412, 443, 490, 510, 555 and 670 nm as standard

level L2 products with pixel size 1.1 × 1.1 km, collected during the NASA global ocean mission in the 1999–2004. The second data set involves the daily estimates of the near-water before-noon wind vectors obtained at 15′ spacing with the scatterometer QuickScat in 1999–2004 and available at http://poet.jpl.nasa.gov. We restricted ourselves to eight wind velocity directions with the following designations and mean azimuths φi: S-N, φ1 = 0°; SW-NE, φ2 = 45°; W-E, φ3 = 90°; NW-SE, φ4 = 135°; N-S, φ5 = 180°; NE-SW, φ6 = 225°; E-W, φ7 = 270°; SE-NW, φ8 = 315°. Any wind vector in the range φi ± 22°30′ was assigned to the i-th direction. The SeaWiFS and QuickScat data and the bottom bathymetry were displayed for every year day (YD) as superimposed maps of the testing area (Figure 2).