The wavelength of satellite reflectance maximum as a remote indicator of water exchange between ecologically different aquatic areas

Abstract

The wavelength λmax of the maximum of spectral reflectance Rrs is examined as a tool for remote indication of water exchange in straits, coastal zones, and other transition areas. Estimates of λmax were calculated from data of MODIS-Aqua sensor by means of spline interpolation of Rrs at 469, 488, 531, 547, and 555 nm for pixels of images of the strait of Skagerrak and the North Caspian Sea as testing areas of active water exchange. The distributions of Rrs(555) and color index Q = Rrs(555)/Rrs(488), found from the same data, were used to compare the behavior of λmax with the variability of habitual characteristics. We demonstrate that the new indicator λmax, being a characteristic of chromaticity of natural waters, is preferable in areas where water exchange is accompanied by redistribution of colored dissolved organic matter of natural origin. The estimates of λmax may be useful as a remote indicator of salinity deficit in river mouth regions.