J/A+A/573/A72 Planetary atmosphere radiative transport code (Garcia Munoz+ 2015)
Pre-conditioned backward Monte Carlo solutions to radiative transport in
planetary atmospheres. Fundamentals: Sampling of propagation directions in
polarising media.
Garcia Munoz A., Mills F.P.
<Astron. Astrophys. 573, A72 (2015)>
=2015A&A...573A..72G 2015A&A...573A..72G
ADC_Keywords: Models, atmosphere ; Planets
Keywords: polarization - radiative transport
Abstract:
The interpretation of polarised radiation emerging from a planetary
atmosphere must rely on solutions to the vector Radiative Transport
Equation (vRTE).Monte Carlo integration of the vRTE is a valuable
approach for its flexible treatment of complex viewing and/or
illumination geometries and because it can intuitively incorporate
elaborate physics.
We present a novel Pre-Conditioned Backward Monte Carlo (PBMC)
algorithm for solving the vRTE and apply it to planetary atmospheres
irradiated from above. As classical BMC methods, our PBMC algorithm
builds the solution by simulating the photon trajectories from the
detector towards the radiation source, i.e. in the reverse order of
the actual photon displacements.
We show that the neglect of polarisation in the sampling of photon
propagation directions in classical BMC algorithms leads to unstable
and biased solutions for conservative, optically-thick,
strongly-polarising media such as Rayleigh atmospheres. The numerical
difficulty is avoided by pre-conditioning the scattering matrix with
information from the scattering matrices of prior (in the BMC
integration order) photon collisions. Pre-conditioning introduces a
sense of history in the photon polarisation states through the
simulated trajectories.
Description:
Files are:
* readme.txt
* Input files: INPUT_hazeL.txt, INPUT_L13.txt, INPUT_L60.txt;
they contain explanations to the input parameters.
Copy INPUT_XXXX.txt into INPUT.dat to execute some of the examples
described in the reference.
* Files with scattering matrix properties:
phF_hazeL.txt, phF_L13.txt, phF_L60.txt
* Script for compilation in GFortran (myscript)
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
readme.txt 79 62 Explanations
INPUT.dat 100 37 Input file
INPUT_L13.txt 100 46 Input file
INPUT_L60.txt 100 46 Input file
INPUT_hazeL.txt 100 47 Input file
PBMC.f90 164 1019 Fortran code
myscript 51 1 Script for compilation in GFortran
phF_L13.txt 63 1801 File with scattering matrix properties
phF_L60.txt 63 1801 File with scattering matrix properties
phF_hazeL.txt 63 1801 File with scattering matrix properties
--------------------------------------------------------------------------------
Acknowledgements:
Antonio Garcia Munoz, tonhingm(at)gmail.com
(End) Patricia Vannier [CDS] 26-Aug-2014