Modelling the optical properties of suspended particulate matter of coral reef environments using the finite difference time domain (FDTD) method |
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| Authors: | John Hedley |
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| Institution: | (1) ARGANS Ltd, 19 Research Way, Tamar Science Park, Derriford, Plymouth, PL6 8BT, UK |
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| Abstract: | The optical scattering properties of non-spherical calcium carbonate particles were modelled using the finite difference time
domain (FDTD) method. This algorithm is computationally expensive but an implementation running on a standard computer’s graphics
processing unit (GPU) provided up to 40 times speed increase and made feasible several thousand model runs for particles up
to size parameter 33 (4 μm for a wavelength of 376 nm in water). The model evaluates all coefficients of the single-particle
Mueller matrix and, when applied to spheres in this size range, compares closely to Mie theory. The modelled unpolarised and
polarised angular irradiance scattering from elongate calcium carbonate spicules displayed many differences from that of spheres
of equivalent volume. Scattering features were observed that are not immediately obvious consequences of spicule geometry.
The extinction efficiency of these particles is also less than that of spheres of equivalent volume. These results suggest
both potential consequences of the non-sphericity of particles on instrument calibration and radiative transfer modelling,
and opportunities for information extraction by polarimetry. |
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