Hyper spectral reflectance from coastal and estuarine waters of Goa

Abstract

The hyper spectral signature of the coastal and estuarine waters of Goa, on a cloud free day, has been computed considering the zenith and azimuthal geometry of sun, satellite and object. The computation begins with the spectral extraterrestrial solar irradiance on the day of observation. Based on single scattering albedo with non-scattering ozone layer and scattering air molecules and attenuating aerosols, within the atmosphere, the model computes the down welling irradiance at the sea surface. From the illumination of the sea surface and further interaction of light with hydrosols and water molecules the model computes the radiance emanating from water body for every 1nm in the 400-700 nm spectral range. The computation agrees spectrally with the observations of L_w, measured using a radiometer, within rms error of plus or minus 9.0 percent, plus or minus 13.9 percent, plus or minus 22.0 percent , plus or minus 16.0 percent, plus or minus 6.5 percent , plus or minus 11.9 percent , plus or minus ii.4 percent, at wavelengths 412, 443, 490, 510, 555, 670 and 683 respectively. A correlation (R2) of 88 percent, 94 percent, 90 percent and 93 percent is obtained between the measured and computed radiances.