Simulating irradiance of water layers of natural reservoirs by solar radiation in various spectral ranges

The study is devoted to numerical simulating the 3D fields of biologically active solar light irradiance at deep water layers of natural reservoirs.

A numerical model has been developed on the basis of the discrete ordinate and Monte-Carlo stochastic methods which allows simulating the propagation of solar radiation in the inhomogeneous atmosphere and water media.

A software package has been elaborated enabling to numerically simulate both the irradiance of the reservoir surface by the total (direct and diffused) solar radiation in the spectral range of λ = 280 - 800 nm under various conditions (season, zenith angle, cloud cover, aerosol parameters, etc.) and the radiation propagating in the heterogeneous water media including absorbing pigments, phytoplankton and particles of the organic residues.

The software package combines atmospheric and water modules being able to function both jointly and separately thus allowing one to use spectral irradiance or integrated signals experimentally measured by ground-based devices and immersion photometric systems to validate the results of numerical calculations and model calibration.

To compute three-dimensional scenes of water body irradiation the super-cluster hardware and parallelization algorithms were used as well as the option to trace back in the Monte-Carlo method implementation.

A set of numeric experiments were made to simulate the 3D irradiance field in the water media of the Naroch group lakes using the measured transparency spectra of natural water probes.

The research was focused on propagating the UV-B, UV-A solar radiation, having the main abiogenic effects such as DNA or the immunity suppression.

The numerical simulation exploiting the refined model of UV transparency and irradiances of water layers at various depths was in a good agreement with experimental data.