REFERENCE FORWARD MODEL

Latest release: RFM v4.34 (1st Oct 2015)

Local Pages


Introduction

The RFM is a GENLN2-based line-by-line radiative transfer model originally developed at
AOPP, Oxford University, under an ESA contract to provide reference spectral calculations for the MIPAS instrument launched on the ENVISAT satellite in 2002.

It has subsequently developed into a general purpose code suitable for a variety of different spectroscopic calculations.

RFM maintenance and development is currently supported by the UK National Centre for Earth Observation (NCEO).

The main design features are

I'll consider adding other features that people would find useful, including combinations of features which are currently not allowed. Just let me know, along with any bug-reports.

To get a copy, email me with a brief statement on what you're planning on using it for and I'll email you the source code.

Anu Dudhia ( anu.dudhia@physics.ox.ac.uk )

Things the RFM can handle...

(Not all of these are compatible - see User's Manual for the full list of 'flags').

Things the RFM can't handle...

HITEMP Data

The RFM v4.3 uses the new Gamache TIPS functions which should be valid up to 3000K. However, the standard HITRAN compilation (based on modelling atmospheric transmittances) excludes many vibrational transitions which become significant at high temperature. Instead these are available as separate compilations (for each molecule and spectral range) on the HITRAN ftp site in the HITEMP-2010 directory.

To use these with the RFM you will first need to merge these into a single HITRAN-type file (eg using mrghit), then run hitbin to convert these to the binary file required by the RFM.

GEISA

GEISA is an alternative spectroscopic database to HITRAN in a different, more extended format.

To use GEISA line data with the RFM you first have to convert it to HITRAN format, eg using the geihit program, then convert to a binary file using hitbin.

GEISA contains additional molecules and isotopologues compared to HITRAN 2012, and the geihit program gives you the option of including or excluding these in the conversion (the RFM can also handle these new molecules).

To use GEISA cross-section data with the RFM you first have to convert it to HITRAN format, eg using the geixsc program, then convert it to RFM format using hitxsc.

UV Data

Radiative transfer in the ultra-violet is dominated by molecular scattering so the RFM cannot be used to calculate meaningful radiances. However it is still useful for calculating the molecular absorption component.

The HITRAN 2012 line database extends into the UV (>25 000 cm-1, <0.4 µm) but only for a limited set of molecules with well-resolved lines (see HITRAN web-site): H2O (<25 711 cm-1), HCl (<34 250 cm-1), H2 (<36 406 cm-1) and HF (<47 365 cm-1).

For other gases, absorptions are available as cross-section tabulations, in the same format as for the infrared heavy molecules, and so can be handled by the RFM in the same way. Note that for molecules which are normally represented in the infrared by HITRAN line data (eg O3) to specify cross-section data you have to append the letter 'x' (eg 'O3x') in the RFM driver table *GAS section - see also Recognised Molecules below, molecule numbers 171-184.

Publications

If you publish anything involving the RFM in the scientific literature...

Recognised Molecules

The following is a list of all the molecules (Names in Red) recognised by the new RFM v4.3 (although see
User's Manual for list for earlier RFM versions up to v4.29, also for the list of recognised Isotopologues). If the last letter is 'q' this is a line molecule which is normally expected to be represented by tabulated cross-section data, and vice-versa for 'x'.

Molecules 1-47 follow the assigments for HITRAN 2012
ID Molecule ID Molecule ID Molecule ID Molecule ID Molecule
1 H2O 2 CO2 3 O3 4 N2O 5 CO
6 CH4 7 O2 8 NO 9 SO2 10 NO2
11 NH3 12 HNO3 13 OH 14 HF 15 HCl
16 HBr 17 HI 18 ClO 19 OCS 20 H2CO
21 HOCl 22 N2 23 HCN 24 CH3Cl 25 H2O2
26 C2H2 27 C2H6 28 PH3 29 COF2 30 SF6q
31 H2S 32 HCOOH 33 HO2 34 O 35 ClONO2q
36 NO+ 37 HOBr 38 C2H4 39 CH3OHq 40 CH3Br
41 CH3CNq 42 CF4q 43 C4H2 44 HC3N 45 H2
46 CS 47 SO3 48 [not assigned] 49 [not assigned] 50 BrOq
51 GeH4 52 C3H8q 53 C2N2 54 C3H4 55 HNC
56 C6H6q
Key Standard HITRAN line molecules
HITRAN line data normally represented as cross-sections
Additional GEISA or other (BrO) line molecules (RFM-specific IDs) - RFM v4.31 onwards
Molecules 100+ are RFM-specific indices for species represented by infrared absorption cross-section data.
ID Molecule ID Molecule ID Molecule ID Molecule ID Molecule
100 Aerosol
General Heavy Molecules
101 ClONO2 102 N2O5 103 SF6 104 CCl4 105 HNO4
106 SF5CF3 107 BrONO2 108 ClOOCl 109 X109 110 X110
CFCs (ChloroFluoroCarbons)
111 F11 (CCl3F) 112 F12 (CCl2F2) 113 F113 (C2Cl3F3) 114 F114 (C2Cl2F4) 115 F115 (C2ClF5)
116 F116 (C2F6) 117 F13 (CClF3) 118 F14 (CF4)
HCFCs (HydroChloroFluoroCarbons)
121 F21 (CHCl2F) 122 F22 (CHClF2) 123 F123 (CHCl2CF3) 124 F124 (CHClFCF3) 125 F141b (CH3CCl2F)
126 F142b (CH3CClF2) 127 F225ca (CHCl2CF2CF3) 128 F225cb (CClF2CF2CHClF)
HFCs (HydroFluoroCarbons)
131 F125 (CHF2CF3) 132 F32 (CH2F2) 133 F134 (CHF2CHF2) 134 F134a (CFH2CF3) 135 F143 (CF3CH3)
136 F143a (CF3CH3) 137 F152a (CH3CHF2) 138 F365mfc
MHCs (Methylated Hydrocarbons)
141 CH3OH (Methanol) 142 CH3CN (AcetoNitrile) 143 CH3CHO (Acetaldehyde) 144 Acetone (CH3COCH3) 145 PAN (CH3C(O)OONO2)
NMHCs (Non-Methylated Hydrocarbons)
151 C2H6x (Ethane) 152 C3H8 (Propane) 153 C6H6 (Benzene) 154 C2H2x (Acetylene) 155 C2H4x (Ethylene)
Halocarbons
161 C4F8 (Octafluorocyclobutane)
UV Cross-sections of simple molecules
171 O3x 172 N2Ox 173 SO2x 174 NO2x 175 H2COx
176 BrO 177 NO3 178 OClO
UV Cross-sections of heavy molecules
181 C7H8 (Toluene) 182 oxylene (o-C8H10) 183 mxylene (m-C8H10) 184 pxylene (p-C8H10)
Key Extinction cross-section [km-1]
Molecular cross-section [cm2/molec]
Dummy names for user-supplied cross-section molecules
Cross-section normally represented as HITRAN line data
Additional GEISA Cross-section molecules - RFM v4.31 onwards
UV Cross-sections - RFM v4.31 onwards
Some molecules are represented by both HITRAN line parameters and as cross-section data.

See User's Manual for more information.
Atmospheric, Oceanic and Planetary Physics Home Page