Retrieval of CPA Concentrations from the Spectral Composition of Subsurface Water Column Diffuse Reflectance: Application to Environmental Remote Sensing Tasks

Abstract

Chapter 18 opens with a concise review of physical and methodological approaches addressing the retrieval of CPAs in waters of different optical complexity. It is explained why the determination of phytoplankton chlorophyll concentration in clear waters can be affected via using relatively simple two or three band-ratio algorithms based on statistically ample in situ data and frequently involving a semi-analytical expressions. However, much more sophisticated methods (illustrated in Chapter 18 by the Levenberg-Marquardt technique as an example) are required to remotely sense phytoplankton chlorophyll in turbid/strongly absorbing waters: in such cases, it is mandatory to simultaneously determine the concentrations of all coexisting CPAs. Only then the concentration of chlorophyll can be accurately determined. Besides, the simultaneously retrieved concentrations of other main CPAs are important for interpreting the ecological state of the waters under investigation.

The reader is offered a set of combinations of CPAs (i.e. hydro-optical situations, all of which are subsumed under the category of case II waters) for which the exercises should be performed. The Practice no. 17 is designed in such a way that the reader have to creatively apply the respective computer program in order to attain the CPA retrievals at the highest possible accuracy.