Radiative transfer theory in the ocean aims to quantify all the processes in the ocean that affect the direction and quantity of photons. The forward problem for remote sensing is to predict the spectral intensity of the light reaching a sensor based on a quantitative description of all the absorption, scattering and attenuation characteristics of the optical components in the ocean.

The light that arrives at the sea surface is already considerably modified from that which reached the top of the atmosphere. The intensity and spectrum are changed by the absorption and scattering of the gases and aerosols, and the directionality has been changed by the scattering. In addition to direct sunlight there is now also a large amount of diffuse light, the intensity and spectrum of which depends on the solar zenith angle and the nature and distribution of aerosols and gases. The sea surface can be characterized by a directional slope spectrum of the waves. This spectrum determines the refraction and reflection patterns at the surface, and so the directional pattern of the light beneath the surface. In addition to the slope spectrum, the sea surface can generate white caps and bubbles, which also affect the redistribution of light.

The sea water itself has certain scattering and absorption characteristics. In addition, the water contains particles of various origins and dissolved materials, each with its own optical characteristics. A fraction of the light that reaches the sea surface and penetrates into the water is reflected back into the atmosphere. In shallow waters some light may reach the bottom and be reflected upwards.

Describing all these events requires the exact definition of radiometric quantities, definitions of the inherent optical properties (the scattering and absorption characteristics of the various oceanic constituents) and apparent optical properties (AOP) that describe the attenuation characteristics of the light field. All of these parameters must then be combined with the incident radiance distribution in physical relations that allow mathematical calculations. This is known as the radiative transfer equation.

More about WET Labs instruments that provide information about scattering, and absorption and attenuation.

More information:
Article by J.R.V. Zaneveld and E. Boss: The Influence of Bottom Morphology on Reflectance Theory and 2-d Geometry Model

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