Table of Contents

# Overview of radiative transfer models for remote sensing

This table gives an overview of the reviewed radiative transfer models. It is beyond the scope of the study to provide a complete list of radiative transfer codes developed since the 1950s. The list should include the codes that are currently used in the remote sensing community. The models are sorted into various categories to structure this table a little bit. The sorting is for several models ambiguous, since they would belong in more than one category. Details about the models and references are given in WP1100 report.

## Comprehensive radiative transfer packages

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

libRadtran RT solvers | UV/VIS/IR | correlated-k | 1D pp or sp / 3D pp | m,r,c,a | Lambert/ BRDF/ spectral albedo | - | yes | - | - | GPL | modular, 10 RT solvers may be selected depending on application |

SCIATRAN | UV/VIS/NIR | correlated-k | 1D pp, psp or sp | m,r,c,a | Lambert/ BRDF/ spectral albedo | yes | - | yes | yes | SU | mainly used for SCIAMACHY retrievals |

AER | UV, VIS, IR, microwave | line-by-line, correlated-k | 1D pp | m,r,c,a | Lambert | - | - | - | - | PD | well validated, widely used, simple fast parameterization for treatment of scattering |

ARTS | microwave, sub-mm | line-by-line | 1D/3D sp | m,c | Lambert/ Fresnel | yes | yes | yes | - | GPL | so far mostly applied and validated for microwave region |

ECSim | UV/VIS/IR/ microwave | ? | 1D/3D | m,c,a,r | BRDF | - | yes | - | - | PD | Monte Carlo; Lidar /w doppler shift; Radar |

SHDOM | UV/VIS/IR/ microwave | correlated-k | 1D/2D/3D pp | m,r,c,a | Lambert/ BRDF | - | - | - | - | PD | 3D radiative transfer model not based on Monte Carlo |

SBDART | VIS/IR | correlated-k/ band model | 1D pp | m,r,c,a | Lambert/ spectral albedo | - | - | - | - | PD | spectral surface reflectivity models |

STREAMER | UV/VIS/IR | correlated-k | 1D-pp | m,r,a,c | Lambert/ BRDF/ spectral albedo | - | - | - | - | PD | web interface |

MODTRAN | UV/VIS/IR | correlated-k (15cm-1), band model (2 cm-1) | 1D-pp / spherical | m,r,c,a | Lambert/ BRDF | - | - | yes | - | L ~$300 | widely-used; non-disclosure agreement to be signed before use |

## Radiative transfer solvers

##### Discrete ordinate methods

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

DISORT | UV/VIS/IR/ microwave | monochr. | 1D pp | m,r,c,a | Lambert/ BRDF | - | - | - | - | PD | very well validated, very efficient |

VDISORT | UV/VIS/IR/ microwave | monochr. | 1D pp | m,r,c,a | Lambert/ BRDF | - | yes | - | - | AOR | vector version of DISORT, but not widely used |

COART | UV/VIS/IR | band model | 1D pp | m,r,c,a | ocean included as model layer | - | - | - | - | NA | ocean-atmosphere coupling, online version available |

SHARM (-3D) | UV/VIS/NIR | monochr. | 1D/3D pp | m,r,a | 2D-BRDF | - | - | - | - | PD | efficient treatment of 2D surface (BRDF) with 1D atmosphere above |

##### Matrix operator methods

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

MOM | UV/VIS/IR | exponential sum fitting | 1D pp | m,r,c,a | Lambert/ BRDF | - | - | - | - | AOR | Code available at DLR |

RTMOM | UV/VIS/IR | correlated-k | 1D pp | m,r,c,a | Lambert/ BRDF | - | - | - | - | PD | Fortran 90 |

MOMO | UV/VIS/NIR | monochr. | 1D pp | m,r,c,a | Cox&Munk, ocean incl. as model layer | - | (yes) | - | yes | NA | ocean-atmosphere coupling, chlorophyll fluorescence |

STAR | UV/VIS | optimized wavelength grid | 1D pp | m,r,c,a | Lambert, spectral albedo | - | - | - | - | SU | computation of erythemal dose and daily dose |

##### Monte Carlo methods

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

MYSTIC | UV/VIS/IR | monochr./ correlated-k | 3D pp, 1D pp or sp | m,r,c,a | Lambert/ BRDF/ topography | - | - | - | - | NA | integrated in libradtran |

MCARaTS | UV/VIS/IR | monochr. | 3D pp | m,r,c,a | Lambert/ BRDF/ topography | - | - | - | - | PD | camera-like images as output |

GRIMALDI UNIK | UV/VIS | monochr./ broadband (effective abs. coeff.) | 3D pp | m,r,c,a | Lambert | - | - | - | - | SU | no further development |

I3RC community model | UV/VIS/IR | monochr. (?) | 3D pp | m,r,c,a | Lambert/ BRDF | - | - | - | - | SU | Monte Carlo community model |

MCC++ | UV/VIS | monochr. | 1D sp | m,r,a | Lambert | yes | yes | - | - | NA | Monte Carlo code that computes Jacobians for Stokes vector |

##### Doubling and adding methods

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

polradtran | UV/VIS/IR/ microwave | monochr. | 1D pp | m,r,c,a | Lambert/ Fresnel | - | yes | - | - | PD | doubling-and-adding method to solve RTE |

DAK | UV/VIS/NIR | monochr. | 1D pp | m,r,c,a | Lambert | - | yes | - | - | NA | no detailed description in the literature |

##### Successive orders of scattering methods

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

LOA | UV/VIS | monochr. | 1D-pp | m,r,a | Lambert/ BRDF | - | yes | - | - | AOR | several versions for different applications |

## Line-by-line models

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

RFM | IR | line-by-line based on GENLN2 | 1D sp or pp | m | Lambert | yes | - | ? | - | SU | no scattering, mainly used for MIPAS |

4A | IR 600-3000cm-1 | ATLAS line-by-line database, based on GEISA | 1D sp | m | blackbody | yes | - | - | - | SU | high spectral resolution, no scattering |

KOPRA | mid-IR | line-by-line | 1D sp | m,a,c | Lambert | yes | - | yes | - | NA | mainly used for MIPAS retrievals, single scattering approx. |

MIRART | microwave/ IR | line-by-line | 1D sp | m | Lambert | yes | - | yes | - | NA | user friendly Python interface tools |

genln-2 | IR/ microwave | line-by-line | 1D pp or sp | m | Lambert | - | - | yes | - | AOR | no further development |

LINEPAK | IR/ microwave | line-by-line | 1D sp | m | blackbody | - | - | yes | - | L | version with limited functionality available online: spectralcalc |

## Fast radiative transfer models

model name | spectral range | spectral calculation | model geometry | atmos. | surface | Jac. | pol. | ref. | Ram. | avail. | specials |
---|---|---|---|---|---|---|---|---|---|---|---|

RTTOV internal description | IR/ microwave | using coefficients based on line-by-line | 1D pp | m,c,a | Lambert | yes | - | - | - | SU | very fast RT by channel precalculation; widely used in variat. assimil., simple parameterisation to handle scattering |

6S | UV/VIS/NIR | lookup-table | 1D pp | m,r,a | Lambert/ BRDF | - | yes | - | - | PD | surface environment |