| Thermal infrared (IR) radiometry from satellite and aircraft platforms provides the ocean scientist with perhaps the best means to image synoptically over wide areas sea surface temperature (SST) distributions, internal waves, fronts, eddies, and upwelling of plankton-rich coastal waters.; Image interpretation accuracy suffers from the scarcity of sea truth data that is needed to calibrate the gray level scales to relate the radiometric observations to the actual surface temperatures. Variations in sea surface emissivity has generally been discounted as having a significant influence on these interpretations, even though it is recognized that as little as a 1 percent change in emissivity can result in a 2{dollar}spcirc{dollar}C difference in SST.; The results of my research using several different radiometers with different band passes show that under controlled laboratory conditions, emissivity of Delaware Bay seawater does in fact vary between 0.987 and 0.971 in a predictable way as a function of temperature, salinity, and suspended sediment concentration over a range of 10 mg/l to 100,000 mg/l. Suspensions were prepared from organic and inorganic Delaware Bay sediments which were found to have particle size distributions near 0.2 {dollar}mu{dollar}m. The comparable fresh (tap) water emissivity function is significantly different in that it is almost completely independent of suspended sediment concentration. Observations also show that where the emissivities of organic and inorganic sediments are distinguishable from one another in seawater, they are essentially identical in fresh (tap) water.; By systematically applying known visible and near-IR wavelength remote sensing techniques that are able to resolve values of suspended sediment concentration and salinity of the water column, a scheme is proposed for deriving corrected values of sea surface emissivity using the emissivity models developed in this research.; Future studies are needed to (1) explore more closely the effect on sea surface emissivity with changes in salinity for various concentrations of suspended sediments; (2) observe the effects of slicks and the thermal boundary layer on emissivity; and (3) determine the effect of particle size and distribution on emissivity. |
