imcrt

ice Monte Carlo Radiative Transfer.

Dependencies

A working installation of Matlab or GNU Octave. Confirmed to run on Matlab R2020b and Octave 7.2.0, but it should run on any recent release, and there should not be any toolbox dependencies.

Install

Run Setup.m. If running in Octave, check .octaverc.

Usage

Run mcrt_verify.m to verify model accuracy. There are three simulations that compare model output with van De Hulst's tabulated solutions to the transfer equation. It could easily be modified for a different problem by setting the inherent optical properties and geometry to new values.

The examples directory includes code needed to reproduce the detector interference simulations reported in the paper below. If you wanted to investigate the influence of an instrument on optical measurements, that code would be a good place to start (e.g. see rodintersect.m).

For general use, there is a library of "inherent optical properties" (scattering and absorption coefficients) for water ice Ih saved in dat/mie_iops_dE.mat. The prefix mie_ refers to the Mie scattering formulas used to compute the scattering coefficients. The suffix _dE refers to the "delta Eddington" approximation used to compute the extinction coefficients: $c=\sqrt{3ab_e}$ with extinction coefficient $c$, absorption coefficient $a$, and effective (or 'reduced') scattering coefficient $b_e$. Note that this equation is identical to the diffusion approximation, where $c$ is sometimes called the "propagation coefficient". It's inverse $1/c$ is the "transport length". See doc/tc-2020-53-supplement.pdf for more details on how these values enter into the Monte Carlo model. In addition, dat/ssa_iops_dE.mat contains the same values of absorption coefficient, but values of scattering and extinction coefficient computed with the "specific surface area" approximation, which is also called the "geometric optics" approximation. This approximation is valid for scatterers about the same size or slightly larger than the interacting wavelengths. The effective particle radii are saved in the libary as well.

How do I cite this?

If you find this model useful, please consider citing the software release (see CITATION.cff), and/or the following paper:

Cooper, M.G., Smith, L.C., Rennermalm, A.K., Tedesco, M., Muthyala, R., Leidman, S.Z., Moustafa, S.E., Fayne, J.V., 2021. Spectral attenuation coefficients from measurements of light transmission in bare ice on the Greenland Ice Sheet. The Cryosphere 15, 1931–1953. https://doi.org/10.5194/tc-15-1931-2021

@article{cooper_2021_TC,
  title = {Spectral Attenuation Coefficients from Measurements of Light Transmission in Bare Ice on the {{Greenland Ice Sheet}}},
  author = {Cooper, M. G. and Smith, Laurence C. and Rennermalm, {\AA}sa K. and Tedesco, Marco and Muthyala, Rohi and Leidman, Sasha Z. and Moustafa, Samiah E. and Fayne, Jessica V.},
  year = {2021},
  month = apr,
  journal = {The Cryosphere},
  volume = {15},
  number = {4},
  pages = {1931--1953},
  publisher = {{Copernicus GmbH}},
  issn = {1994-0416},
  doi = {10.5194/tc-15-1931-2021},
  langid = {english}
}

More details

The model roughly implements the one described in Wang et al. (1995). It is not meant to be an exact implementation. The model simulates transfer through a uniform slab. See doc/tc-2020-53-supplement.pdf and the two references for technical descriptions.

Wang, L., Jacques, S. L. and Zheng, L.: MCML?Monte Carlo modeling of light transport in multi layered tissues, Computer Methods and Programs in Biomedicine, 47(2), 131?146, https://doi.org/10.1016/0169 2607(95)01640 F, 1995.