Hi Uma,
thanks for your interest!
The type of observations I'm concerned with are not only aerosol optical depth (AOD) as column integrated property, but also ground-based in-situ observations of particle size distribution, scattering and absorption coefficient that are representative for the surface level. These are usually measured at "dry-state", i.e. at RH < 40% where aerosol humidity growth is negligible.
Traditionally, model-observation comparisons have relied on AOD observations since AOD is a diagnostic parameter, it's usually output directly by the model, and it can be measured directly. The other observations I'm talking about contain much more detailed information about the aerosol, but they are not part of the usual model output, even though that would be possible in principle. The reason why I have proposed my long list of variable names is twofold: 1) the CF convention contains a really well structured and well organized framework for variable naming (that alone would be reason enough); 2) I'd like to foster the use of those observations in the WMO GAW network that are so far underused for model comparisons.
What has that to do with your proposed name for aerosol Mie scattering, especially since pure Mie scattering is a theoretical construct and therefore can't be measured? The syntax of the name you proposed originally, "volume_extinction_coefficient_in_air_due_to_mie_scattering_of_ambient_aerosol", would have conflicted with a whole other suite of names of measurable quantities I just proposed, which follow the syntax "volume_scattering_coefficient_in_air_due_to_dry_aerosol". This is why I proposed "volume_scattering_coefficient_in_air_due_to_ambient_aerosol_assuming_mie_scattering" for your Mie scattering variable, where the syntax of both is in agreement.
Was that helpful at all?
Best regards,
Markus
_______________________________________
Dr. Markus Fiebig
Dept. Atmospheric and Climate Research (ATMOS)
Norwegian Institute for Air Research (NILU)
P.O. Box 100
N-2027 Kjeller
Norway
Tel.: +47 6389-8235
Fax : +47 6389-8050
e-mail: Markus.Fiebig at nilu.no
skype: markus.fiebig
-----Original Message-----
From: Shankar, Uma [mailto:ushankar at unc.edu]
Sent: Freitag, 9. M?rz 2012 03:03
To: X:m.schultz at fz-juelich.de; Markus Fiebig; cf-metadata at cgd.ucar.edu
Subject: RE: warming up old stuff - part 1: aerosol mie scattering
Hi Martin and Markus -
At present CMAQ doesn't output extinction coefficients directly (although post processing can produce those outputs, but that is not a standard model application). However it's quite likely that the coupled WRF-CMAQ, due for public release in the near future, will have the full complement of aerosol optical properties in the output files. I will pass along to the responsible people at EPA. I agree with Markus that if the name represents measured as well as modeled quantities the name should be more universally applicable. I'm not sure that optical depth measurements give you the scattering coefficient though - I have seen extinction and absorption optical depths from which you would need to use a retrieval algorithm to get anything columnar or level-specific for the relevant coefficient. Would appreciate your feedback.
Thanks -
Uma
---------
Uma Shankar, Research Associate
Institute for the Environment
Bank of America Plaza CB# 6116
137 E. Franklin St Room 644
Chapel Hill NC 27599-6116
Phone: (919) 966-2102
Fax (919) 843-3113
Mobile: (919) 441-9202
In order that people may be happy in their work, these three things are needed: they must be fit for it; they must not do too much of it; and they must have a sense of success in it. -John Ruskin, author, art critic, and social reformer (1819-1900)
-----Original Message-----
From: Schultz, Martin [mailto:m.schultz at fz-juelich.de]
Sent: Wednesday, March 07, 2012 5:16 AM
To: Markus Fiebig; cf-metadata at cgd.ucar.edu
Cc: Shankar, Uma
Subject: RE: warming up old stuff - part 1: aerosol mie scattering
Dear Markus,
thanks for the thoughtful response. I cc this to Uma Shankar who had sent me the RSIG (
http://badger.epa.gov/rsig/) CMAQ variable list from where this suggestion originated. CMAQ is of course a model. I don't think it would hurt to have also standard_names for pure model quantities, but I agree with you that one may have to phrase and define this more clearly. The name you propose is already in the list, and the suggestion was to include a more specific term to denote the specific contribution from Mie scattering.
Best regards,
Martin
PS: original proposal was
"* How can we get more specific about the "extinction coefficient"? In particular, we would like to express something like "..._due_to_Mie_scattering". But does this work with " volume_extinction_coefficient_in_air_due_to_ambient_aerosol". The new name would then become "volume_extinction_coefficient_in_air_due_to_Mie_scattering_of_ambient_aerosol" ? (and would "Mie" be spelled with "M" or "m"?)"
> -----Original Message-----
> From: Markus Fiebig [mailto:Markus.Fiebig at nilu.no]
> Sent: Wednesday, March 07, 2012 9:31 AM
> To: Schultz, Martin; cf-metadata at cgd.ucar.edu
> Subject: RE: warming up old stuff - part 1: aerosol mie scattering
>
> Dear all,
>
> please excuse if I come in late into this discussion, but I would like
> to make a few comments about the proposed variable name
>
> "volume_extinction_coefficient_in_air_due_to_mie_scattering_of_ambient
> _aerosol"
>
> As it is written above, the name is self-contradicting. The aerosol
> extinction coefficient is defined to include both, particle scattering
> and absorption. The part of the aerosol extinction coefficient that is
> due to particle scattering is commonly referred to as aerosol
> scattering coefficient. Also, I need to apologise for not having
> followed the discussion concerning the use of the term "mie", but it
> appears rather to confuse than to clarify in the context here. Even
> though the term Mie-particle is colloquially used for a spherical,
> internally well mixed aerosol particle, such a particle exists only in
> theory or in some numerical model. If the variable name is also to be used for an observed quantity, which I think it should, the term "Mie" should be avoided.
>
> How about putting this much simpler, and name the property:
>
> "volume_scattering_coefficient_in_air_due_to_ambient_aerosol"
>
> or, to avoid even more confusion:
>
> "volume_scattering_coefficient_at_stp_in_air_due_to_ambient_aerosol"
>
> Regards,
> Markus
>
>
>
> _______________________________________
> Dr. Markus Fiebig
>
> Dept. Atmospheric and Climate Research (ATMOS) Norwegian Institute for
> Air Research (NILU) P.O. Box 100
> N-2027 Kjeller
> Norway
>
> Tel.: +47 6389-8235
> Fax : +47 6389-8050
> e-mail: Markus.Fiebig at nilu.no
> skype: markus.fiebig
>
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Received on Fri Mar 09 2012 - 02:03:27 GMT
