The Methods of Water Spectra Measurement and Analysis I:Above-Water Method

One of basis of water color remote sensing is to obtain and analyze the optical properties of the waterbodies. The optical properties of waters includes two aspects, Apparent Optical Properties(AOPs) and Inherent Optical Properties(IOPs). Generally speaking, there are two relatively independent and complementary methods of in situ AOPs measurements, the profiling method and above water method. This paper focus on an above water method for the measurements of the AOPs which are directly related to the water color sensing parameters. In order to meet ocean color sensing requirements, the in situ measurements have to be able to derive:water leaving radiance L w , the normalized L wN , remote sensing reflectance R rs , irradiance reflectance just beneath water surface R (0 -), etc. NASA ocean optic protocols deal mainly with CASE Ⅰ waters, while the most waterbodies of our coastal zone and lakes are CASE Ⅱ ones. The CASE Ⅱ water related measurement parameterization will be discussed. Some new methods are given for deriving the critical parameters in processing and analysing the data from above water method.