LANDSAT-MSS RADIANCE AS A MEASURE OF SUSPENDED SEDIMENT IN THE LOWER YELLOW RIVER (HWANG HO)

A method of converting the Landsat-MSS radiance to an estimate of suspended sediment concentration is presented in this paper. The CCT data for the Lower Yellow River (Hwang Ho) were used in the study. The data were first corrected for instrumental error due to a drift in the sensor response and then converted to the absolute radiance received by the sensor. In order to understand the detected radiance and its variability, radiative transfer in the earth''s atmosphere and natural waters are discussed. The radiative transfer equation has been simplified, so that a highly accurate atmosphere correction algorithm for diffuse sky radiance may be developed. However, the MSS is more sensitive to the direct sky radiance, and so an atmospheric correction based on the normalization of the solar angle is considered. Following a logarithmic relationship between radiance and suspended sediment concentration, the corrected remote-sensing radiance is used to estimate suspended sediment concentrations in the Lower Yellow River. The results suggest that the relationship could represent a universal algorithm for estimating suspended sediment concentration, although further detailed study will be needed to investigate this property. There is also sufficient evidence to indicate that remote sensing radiance may be used to infer the sediment size distribution, which represents a very important parameter in sediment transport studies. Finally, cross sections of suspended sediment concentration at Lijin in the Lower Yellow River are derived from the satellite data, and a map of sediment distribution in the estuary is also presented.