Hi Alison,
"atmosphere": I wasn't aware that "atmosphere" usually refers to the
whole column in the "CF-world".
cell_method: I don't know what kind of cell methods are allowed.
"pressure: mean" comes close but is not exactly the calculated quantity
because pressure is only approximately proportional to the number of dry
particles. XCO2 is the sum over all CO2 particles in the atmospheric
column divided by the number of dry air particles in the same column.
"dry_atmosphere_mole_fraction_of_carbon_dioxide/methane": Perfect!
Cheers Max
____________________________________________________________________
Dr. Maximilian Reuter
Institute of Environmental Physics (IUP)
University of Bremen, FB1
Otto-Hahn-Allee 1
D-28334 Bremen
Germany
Phone: +49 (421) 218 62085
FAX: +49 (421) 218 62070
E-Mail: maximilian.reu...@iup.physik.uni-bremen.de
http://www.iup.uni-bremen.de/~mreuter
____________________________________________________________________
Am 20.01.2016 um 15:16 schrieb alison.pamm...@stfc.ac.uk:
Dear Max,
Thank you for your comments. (This reply is also being posted to the
CF mailing list so that all subscribers can follow the discussion and
contribute).
In CF, different standard names often do sound quite similar as a
direct result of our efforts to standardize the use of individual
terms and phrases. However, all the terms are carefully defined and
full explanations accompany (almost) every entry in the standard name
table. We have many existing “atmosphere” and “in_air” names and the
distinction between these is precisely that “atmosphere” applies to
the whole column, or in some cases the entire atmosphere, whereas
“in_air” applies to a local value within the medium. We make a similar
distinction in oceanographic names by using “ocean” for column names
and “in_sea_water” for local values. Hence, I think it is appropriate
to use “atmosphere” for your proposed names. I agree with Jonathan’s
advice to also attach a cell_methods attribute to your data variable,
e.g., cell_methods = “height: mean” or cell_methods = “pressure: mean”
depending on your choice of vertical coordinate. This would avoid any
confusion about how the quantity was calculated.
Clearly you do have a requirement to distinguish between ambient and
dry air, so certainly the name should reflect this. Hence I still
favour my suggestions of: dry_atmosphere_mole_fraction_of_methane and
dry_atmosphere_mole_fraction_of_carbon_dioxide. The addition of “dry”
at the beginning of each name would, as you pointed out, help to
further distinguish from the existing “in_air” names. Would this be an
acceptable compromise?
Best wishes,
Alison
*From:*Dr. Maximilian Reuter [mailto:reut...@loz.de]
*Sent:* 20 January 2016 13:25
*To:* Pamment, Alison (STFC,RAL,RALSP); j.m.greg...@reading.ac.uk
*Cc:* michael.buchw...@iup.physik.uni-bremen.de;
veronika.eyr...@dlr.de; Bennett, Victoria (STFC,RAL,RALSP)
*Subject:* Re: [CF-metadata] New standard names for ESA GHG CCI quantities
Hi Alison et al.,
thanks for coming back to the XCO2 and XCH4 CF standard names. As
mentioned in an earlier mail (18.11.2015), I think
atmosphere_mole_fraction_of_carbon_dioxide_in_dry_air could be mixed
up with the already existing name
"mole_fraction_of_carbon_dioxide_in_air". In contrast to
mole_fraction_of_carbon_dioxide_in_air, XCO2 is a column average. At
least for me, "atmosphere" would not automatically imply that a column
average is meant.
Additionally, it makes a difference if the mole fraction is relative
to dry or wet air. The difference is small but in terms of required
accuracy for XCO2 and XCH4, the difference is important and was
subject to many discussions in the past (see also TCCON
<https://tccon-wiki.caltech.edu/Network_Policy/Data_Use_Policy/Auxiliary_Data>).
Therefore, I thinks it is important to specify in the standard name
that XCO2 (and XCH4) are column averages and that they are dry_air
mole fractions.
What about
"column_average_mole_fraction_of_carbon_dioxide_in_dry_air"? On the
one hand, this would be consistent with the naming convention of
"mole_fraction_of_carbon_dioxide_in_air" and on the other hand it
would clearly specify the difference to
"mole_fraction_of_carbon_dioxide_in_air.
Anyway, I'm happy with any name we can get :)
Cheers Max
____________________________________________________________________
Dr. Maximilian Reuter
Institute of Environmental Physics (IUP)
University of Bremen, FB1
Otto-Hahn-Allee 1
D-28334 Bremen
Germany
Phone: +49 (421) 218 62085
FAX: +49 (421) 218 62070
E-Mail: maximilian.reu...@iup.physik.uni-bremen.de
<mailto:maximilian.reu...@iup.physik.uni-bremen.de>
http://www.iup.uni-bremen.de/~mreuter
<http://www.iup.uni-bremen.de/%7Emreuter>
____________________________________________________________________
Am 20.01.2016 um 13:22 schrieb alison.pamm...@stfc.ac.uk
<mailto:alison.pamm...@stfc.ac.uk>:
Dear Jonathan,
I agree that we don't usually combine "atmosphere" and "in_air" in the same
name. My reason for doing it in this case was because the original proposal specified two
conditions:
1) dry air;
2) column average quantity (therefore not local).
I needed to find some way of including both in the name. However, it may be that we don't need
the "dry" bit at all, in which case we could just go with
atmosphere_mole_fraction_of_methane and atmosphere_mole_fraction_of_carbon_dioxide, and there is
no problem. If it really is important that we specify "dry" for these quantities, perhaps
a better solution would be to put it at the start of the name, thus,
dry_atmosphere_mole_fraction_of_methane and dry_atmosphere_mole_fraction_of_carbon_dioxide. Does
that look better?
Best wishes,
Alison
-----Original Message-----
From: CF-metadata [mailto:cf-metadata-boun...@cgd.ucar.edu] On Behalf
Of Jonathan Gregory
Sent: 19 January 2016 16:55
To:cf-metadata@cgd.ucar.edu <mailto:cf-metadata@cgd.ucar.edu>
Subject: [CF-metadata] New standard names for ESA GHG CCI quantities
Dear Alison
In existing names we generally use "atmosphere" to indicate a property
of
the
atmosphere as a whole (or a large portion of it) and "in_air" to
indicate a
local property within the atmosphere. We don't use both phrases at once.
These
quantities can be regarded as means of local properties, I think, so
just
in_air would be sufficient. If no vertical coordinate is specified, it
should
apply to the entire atmosphere, but to make that clear a cell_method
could
be
added to record that it's a vertical mean.
Best wishes
Jonathan
----- Forwarded message fromalison.pamm...@stfc.ac.uk
<mailto:alison.pamm...@stfc.ac.uk> -----
Date: Tue, 19 Jan 2016 16:39:38 +0000
From:alison.pamm...@stfc.ac.uk <mailto:alison.pamm...@stfc.ac.uk>
To:cf-metadata@cgd.ucar.edu <mailto:cf-metadata@cgd.ucar.edu>
CC:veronika.eyr...@dlr.de
<mailto:veronika.eyr...@dlr.de>,victoria.benn...@stfc.ac.uk
<mailto:victoria.benn...@stfc.ac.uk>,
mreu...@iup.physik.uni-bremen.de
<mailto:mreu...@iup.physik.uni-bremen.de>,
michael.buchw...@iup.physik.uni-bremen.de
<mailto:michael.buchw...@iup.physik.uni-bremen.de>
Subject: [CF-metadata] New standard names for ESA GHG CCI quantities
Dear All,
I have been asked to re-propose two standard names that were
originally
proposed by Maximilian Reuter in 2014 but which did not receive any
comments at the time:http://mailman.cgd.ucar.edu/pipermail/cf-
metadata/2014/057373.html.
I have rephrased the original proposal to make the names more CF
like
and have added some standard definition text, so the names are now
proposed as follows:
atmosphere_mole_fraction_of_methane_in_dry_air (canonical units: 1)
'Mole fraction is used in the construction
"mole_fraction_of_X_in_Y",
where X is a material constituent of Y. A chemical species denoted by X
may
be described by a single term such as "nitrogen" or a phrase such as
"nox_expressed_as_nitrogen". The "atmosphere mole fraction" of a
quantity refers to the column average from the surface to the top of the
atmosphere. Methane is a member of the group of hydrocarbons known as
alkanes. There are standard names for the alkane group as well as for
some
of the individual species. The chemical formula for methane is CH4.'
atmosphere_mole_fraction_of_carbon_dioxide_in_dry_air (canonical
units: 1)
'Mole fraction is used in the construction
"mole_fraction_of_X_in_Y",
where X is a material constituent of Y. A chemical species denoted by X
may
be described by a single term such as "nitrogen" or a phrase such as
"nox_expressed_as_nitrogen". The "atmosphere mole fraction" of a
quantity refers to the column average from the surface to the top of the
atmosphere. The chemical formula for carbon dioxide is CO2.'
These names reflect the original proposal, and generally follow
the syntax
of existing names such as mole_fraction_of_carbon_dioxide_in_air. I have
prepended these names with the word "atmosphere" as a way of indicating
a column amount, similar to existing atmosphere_mass_content names.
We don't currently have any "dry_air" names in CF. When this topic
last
came up on the mailing list (as far back as 2008 under the thread
entitled
"mixing ratio") it was concluded that the current "in_air" names don't
tie the
definition down to either dry or ambient air. The reason for this
(deliberate)
vagueness is that numerically the quantities in dry or moist air are
not very
different except in the case of water vapour itself where we define
humidity_mixing_ratio to mean " ratio of the mass of water vapor to the
mass of dry air". The gist of the 2008 conversation was that if we ever
needed to be very precise about making the distinction between ambient
air and dry air then we would be able to introduce appropriate names at
a
later stage, but there wasn't a pressing need at the time. An offline
conversation I had more recently with Jonathan Gregory and Martin
Schultz
went along similar lines, basically saying that we wouldn't change any
existing names where the deliberate impre
ci
sion isn't important, but reiterating that we could introduce new
names if
there are cases where it does matter, specifying dry or ambient.
Please could Maximilan, Veronica or another member of the CCI team
answer the question about whether there is a real need to specify
"dry_air"
in the case of these names, or can we get away with being a bit more
vague?
If vagueness is OK, then the names would simplify to
atmosphere_mole_fraction_of_methane_in_dry_air and
atmosphere_mole_fraction_of_carbon_dioxide. Also, do others agree with
my using "atmosphere" here to indicate the column average? All comments
are welcome.
Best wishes,
Alison
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