Using full scattering data from ARTS database in RTTOV-SCATT

[Lu Rui]

Dear RTTOV support team,

I am writing to inquire about the generation of scattering coefficient files that include phase function information for use with RTTOV-SCATT.

I understand that the official RTTOV distribution provides scattering coefficient files that do not contain the Legendre expansion of the phase function. To generate the necessary coefficient files, the hydro_table_generation.ksh script requires .full files that contain ARTS phase function information.

Could you please advise on the following:

Does RTTOV provide the .full files, or can you provide scattering coefficient files that include the phase function information (i.e., Legendre expansion coefficients)?

If not, what would be the recommended approach to obtain or generate such files for use with RTTOV?

I am specifically interested in implementing the full scattering properties (phase function details) in RTTOV-SCATT for benchmark studies against the operational fast model.

Thank you for your assistance.

[James Hocking]

Hi Lu Rui,

I have made the ARTS database files containing the phase function information available here:
https://nwp-saf.eumetsat.int/downloads/rtcoef_info/data/artsdb_full_phasefn.tar.bz2

To use this with the RTTOV MW hydrotables genration, extract this tarball in the src/mw_scatt_coef/artsdb/ directory.

Note that “RTTOV-SCATT” no longer exists as a separate model in RTTOV v14, which is the only version of RTTOV that supports these full phase function input files.

It is also worth noting that we have observed significant differences (tens of Kelvin) between delta-Eddington and DOM simulations for non-spherical particles (especially snow) at higher frequencies (e.g. 183 GHz channels). The DOM simulations are typically too warm, but we have not yet determined the cause of this. It is not currently believed to be a problem with the DOM implementation in RTTOV as the RTTOV DOM radiances can be replicated in DISORT.

Best wishes,
James

• This reply was modified 1 week, 6 days ago by James Hocking.

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