We have given a review of UV and visible radiative transfer in a CASIO system with an emphasis on basic physical principles. To illustrate applications of the theory we have:
(1) Compared two different models (based on the deterministic discrete-ordinate radiative transfer (DISORT) method and stochastic Monte Carlo simulations)
for radiation penetration into the open ocean, which for a given set of input parameters have been shown to give identical results. Compared measured and modeled radiative transfer in a CASIO system, which reveals that accurate transmittances, as well as accurate values for the radiative energy deposition versus depth, can be calculated using the CASIO-DISORT model.
(2) Discussed results of a study showing that multiple scattering in a highly scattering medium, such as sea ice, gives rise to a marked enhancement of the downward irradiance across the atmosphere-sea ice interface.
(3) Discussed results of a recent study of the primary production in icy polar waters, which, contrary to previous investigations, reveal that a 50% ozone depletion might lead to an increase (~1%) rather than a decrease in primary productivity.
In view of the above, we conclude that:
• for a CAO system, our ability to model the transport of UV radiation and visible light appears to be limited as much by reliable information about optical properties of marine constituents and atmospheric aerosol loading as by our ability to accurately solve the radiative transfer equation;
• multiple scattering in sea ice leads to a significant enhancement of the downward irradiance across the atmosphere-sea ice interface;
• it is important to make field measurements to provide reasonable input to modeling efforts; and
• in icy polar waters, an ozone depletion might lead to an increase rather than a decrease in primary productivity.
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