More than 70% of the earth surface is covered by water, its change and variation has profound effects to our ecosystem and our quality of life. Also, human activity and development affect the ocean-atmosphere system. For this purpose, water properties of the vast ocean have to be efficiently and continually measured. These properties include temperature, salinity, and substance presented in the water. Optical and biogeochemical processes are essentially connected via the interaction of light with particulate and/or dissolved matters in the ocean. As the biomass grows and accumulates, light absorption and scattering become stronger, leading to less light penetration in the water, which in turn provides a negative feedback for the biological activities. The impacts of physical processes on biogeochemical processes have been primarily recognized as horizontal and/or vertical transports of nutrients and plankton biomass. Changes in optical properties through physical processes, which alter underwater light field and further change biological activities. Thus, it is important to model the underwater light field accurately when assessing marine ecosystem. On the other hand, spaceborne microwave radar program has become one of the most important tools in studies of ocean dynamic environment and inversion of oceanographic parameters. They are widely used in extraction of global sea surface wind, wave spectrum and sea surface elevation so on and oil spill detection on sea surfaces. Accurate microwave physical models are essential for the understanding of the remote sensing observations and the development and improvement of the oceanographic parameters inversion algorithm.
Optical models can be divided into two categories, the radiative transfer models which focus on forward modeling, and the parameterized models which can be used in water properties’ retrieval. The main radiative transfer models are as follows: Monte Carlo method[Gordon, 1976; Kirk, 1981; Mobley, 1994; Mobley, et al., 1993; Morel and Gentili, 1991; You, et al., 2009; Zhai, et al., 2010; Zhai, et al., 2013], Invariant embedding method (e.g., HydroLight) [Mobley, 1994; Mobley, et al., 1993], discreet ordinate method (e.g., DIScreet Ordinate Radiative Transfer, DISORT) [Mobley, et al., 1993; Stamnes, et al., 1988], matrix algorithm (e.g., MOMO[Fell and Fischer, 2001; Hollstein and Fischer, 2012]，PCOART[He, et al., 2010]), and the couped ocean-atmosphere radiative transfer models [Bulgarelli, et al., 1999; Fell and Fischer, 2001; He, et al., 2010; Hollstein and Fischer, 2012; Jin, et al., 2006; Jin and Stamnes, 1994; Ota, et al., 2010; Zhai, et al., 2010; Du and Lee, 2014]; There are many paraterized models[IOCCG, 2006]，the physical models which employed by MODIS include: Carder’s semi-analytical algorithm [Carder et al., 1999, Carder et al., 2004]、QAA [Lee et al., 2002, Lee et al., 2011]、GSM’s semi-analytical algorithm [Garver and Siegel, 1997, Maritorena et al., 2002].
Radar backscattering signals are maily dependent on radar frequency, polarization, radar observation geometry and the electromagnetic scattering properties of different types scatters from the ocean. Microwave models can be divided into two categories, the physical models which focus on predicting and interpreting the radar scatter from a dynamic ocean surface and the parameterized models which are mainly used to inverse oceanographic parameters. Most of physical models are approsimation modeling of the radom rough sea surface, e.g. [Elfouhaily & Guerin, 2004; Engen et al., 2006; Kudryavtsev, et al., 2003; Kudryavtsev, et al,.2005; Voronovich and Zavorotny, 2014]. In recent years, more and more efforts are paid to research on a general scattering modeling of the comprehensive ocean scene based on radiative transfer theory. As for the paraterized models, the main ones includs the Ku-band RADSCAT models, the C-band GMFs families, e.g., CMOD4(Stoffelen and Anderson, 1997), CMOD_IFR2(Quilfen, et al., 1998) and CMOD5(Hersbach, et al., 2007) and L-band GMFs (Isoguchi and Shimada, 2009). Among these models, the C-band parametric models are most widely used.
