REFERENCE FORWARD MODEL

Introduction
Things the RFM can handle
Things the RFM cannot handle
Things I'm thinking about
RFM v4.3 (still under development!)
Publications
Recognised molecules

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 launched on the ENVISAT satellite in 2002.

It has subsequently developed into a general purpose code suitable for a variety of different spectroscopic calculations. The main design features are

Easy to use - probably its main advantage
Robustness - you shouldn't be able to crash the program
Portability - written in (almost) standard FORTRAN-77
Efficient coding - attempts to maximise speed while minimising memory
Self-documented code - just in case you need to make you own modifications
On-line documentation - these web pages
Output spectra independent of spectral range (eg value at 901.3 cm-1 will be the same whether you produce a spectrum from 901.2-901.4 cm-1 or from 500-1000 cm-1)

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 ( dudhia@atm.ox.ac.uk )

Things the RFM can handle...

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

Spherical or plane-parallel atmospheres, or homogeneous paths
Field-of-View & Instrument Line Shape convolutions
CO2 Line mixing
Continua for H2O, O2, N2 and CO2
Non-LTE (via user-supplied vibrational temperatures)
Select lines of particular isotopes and/or bands
Jacobians (Weighting functions) for p, T, VMR, line-of-sight pointing and surface temperature and emissitivity
Satellite/Balloon & Aircraft/Ground-based viewing geometries
Surface reflections
Output spectra of radiance, transmittance, absorption, cooling rates, optical depth and/or brightness temperature
Output diagnostics from ray-tracing (including Curtis-Godson integrations)
Output/Input absorption coefficient tabulations k(nu,p,T)
Horizontal structure in the atmosphere
Flux calculations and matrices.
Different isotopic mixing ratio profiles

Things the RFM can't handle...

Scattering (too difficult)
Instrument Line Shapes wider than around 1cm-1 (best done by the user afterwards)

Things I'm thinking about ...

Making the RFM (and hitbin) compatible with the new HITRAN 2004 format (actually, for most purposes, it already is - the only problem is if you try to select out individual vibration levels, eg for non-LTE)

Rewriting the code in Fortran 90 (mainly for the dynamic array sizing)

Putting source code and sample input files on an ftp site (see RFM Downloads)
Setting up a users' e-mail list
Option to read HITRAN ASCII files directly
Rodrigues et al CO2 line-mixing (JQSRT 16, 153)
Spectrally varying surface emissivity

Publications

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

I do not expect to be a co-author, or even consulted. However, I would appreciate it if you sent me a reference for the final publication since it should help me obtain any funding for future RFM development work.
If you want to cite the RFM I'm afraid the best reference is this web-page - there's nothing describing the RFM in the published literature (still on my to-do list!).

RFM v4.3

A significant amount of code development of the RFM has been possible thanks to a grant from NERC EO Mission Support Scheme, NE/F000022/1. These will be incorporated into v4.3 of the RFM, currently undergoing testing. The main changes are

New Molecules: CH3OH (#39), F116 (#82), SF5CF3 (#83), PAN (#84) and CH3CN (#85)
Full compatibility with the HITRAN2004 data (includes 'reverse engineering' the new HITRAN format so that the old 'global quantum indices' are restored)
Updated handling of the Total Internal Partition Sum (TIPS) data - now uses a 4th order interpolation of internally tabulated data rather than the less accurate 4th order polynomial covering the entire temperature range
Conversion tools for the new GEISA format
Niro et al CO2 line-mixing - (the Niro et al code has had to be almost completely rewritten so that the RFM can incorporate this more transparently from the user's point of view).
Extension to allow molecular cross-sections to be used in visible and ultra-violet
Updated RFM ATBD
Option for arbitrary p,T grids when creating Look-Up Tables.
Allow for horizontal structure in vibrational temperature fields

Recognised Molecules

The following is a list of all the molecules that will eventually be recognised by the new RFM v4.3 (although see User's Manual for current list)

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	`CH3OH`	40	`CH3Br`
41	`CH3CN`	42	`CF4`	43	`BrO`	44	`C3H8`	45	`C2N2`
46	`C4H2`	47	`HC3N`	48	`C3H4`	49	`GeH4`
50	`Aerosol`
51	`F11 (CFCl3)`	52	`F12 (CF2CL2)`	53	`F13 (CClF3)`	54	`F14 (CF4)`	55	`F21 (CHCl2F)`
56	`F22 (CHClF2)`	57	`F113 (C2Cl3F3)`	58	`F114 (C2Cl2F4)`	59	`F115 (C2ClF5)`	60	`CCl4`
61	`ClONO2`	62	`N2O5`	63	`HNO4`	64	`SF6`	65	`X65`
66	`X66`	67	`X67`	68	`X68`	69	`X69`	70	`F123` (CHCl2CF3)
71	`F124` (CHClFCF3)	72	`F141b` (CH3CCl2F)	73	`F142b` (CH3CClF2)	74	`F225ca` (CHCl2CF2CF3)	75	`F225cb` (CClF2CF2CHClF)
76	`F32 (CH2F2)`	77	`F125 (CHF2CF3)`	78	`F134` (CHF2CHF2)	79	`F134a (CFH2CF3)`	80	`F143a (CF3CH3)`
81	`F152a (CH3CHF2)`	82	`F116 (C2F6)`	83	`SF5CF3`	84	`PAN`	85	`CH3CN` (AcetoNitrile)
86	`C6H6`	88	`C2H6`	89	`C3H8`	84	`Acetone` (CH3COCH3)
	Key				Standard HITRAN line molecules
					HITRAN line Molecules also represented as cross-sections
					Additional GEISA line molecules (RFM-specific IDs)
					Extinction cross-section [km^-1] (RFM-specific IDs)
					Molecular cross-section [cm²/molec] (RFM-specific IDs)
					Dummy names for extra cross-section molecules (RFM-specific IDs)

See User's Manual for more information.

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