Dear Alison,
I believe your interpretation of the units of integral_wrt_time_of_mole_stomatal_uptake_of_ozone, that they should be "mol m-2" rather than "mol m-2 s-1" as originally proposed is correct, but I've copied Michaela and Michael in so that they can comment. This would mean changing the units of pod0 [Phytotoxic ozone dose] to "mol m-2": is that consistent with what AerChemMIP want from this variable?
regards,
Martin
________________________________
From: Pamment, Alison (STFC,RAL,RALSP)
Sent: 02 May 2018 15:20
To: Juckes, Martin (STFC,RAL,RALSP); Jonathan Gregory; cf-metadata at cgd.ucar.edu
Subject: RE: [CF-metadata] Four standard names for the AerChemMIP data request
Dear Martin and Jonathan,
Thank you for the proposal for four names for AerChemMIP and for the discussion.
1. tendency_of_atmosphere_mole_concentration_of_nitrous_oxide_due_to_chemical_destruction (mol m-3 s-1)
'The phrase "tendency_of_X" means derivative of X with respect to time. Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". The chemical formula for nitrous oxide is N2O. The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "Chemical destruction" means the result of all chemical reactions within the medium (here, atmosphere) that remove a certain amount of a particular species from the medium.'
As Martin has pointed out, this is very similar to existing names. This name is accepted for publication in the standard name table and will be added in the May update.
Martin has also drawn my attention to the fact that one of the existing tendency_of_atmosphere_mole_concentration names contains a stray 'of':
tendency_of_atmosphere_of_mole_concentration_of_carbon_monoxide_due_to_chemical_destruction. Thanks for pointing this out - I will create an alias to correct the typo:
tendency_of_atmosphere_of_mole_concentration_of_carbon_monoxide_due_to_chemical_destruction -> tendency_of_atmosphere_mole_concentration_of_carbon_monoxide_due_to_chemical_destruction.
This will also be done in the May update.
2. volume_scattering_function_in_air_due_to_ambient_aerosol_particles (m-1 sr-1)
'The volume scattering function is the intensity (flux per unit solid angle) of scattered radiation per unit length of scattering medium, normalised by the incident radiation flux. The (range of) direction(s) of scattering can be specified by a coordinate of scattering_angle. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the scattering applies at specific wavelengths or frequencies.The volume scattering function is the fraction of incident radiative flux scattered into unit solid angle per unit path length. The (range of) direction(s) of scattering can be specified by a coordinate of scattering_angle. The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. "Ambient_a
erosol" means that the aerosol is measured or modelled at the ambient state of pressure, temperature and relative humidity that exists in its immediate environment. "Ambient aerosol particles" are aerosol particles that have taken up ambient water through hygroscopic growth. The extent of hygroscopic growth depends on the relative humidity and the composition of the particles. To specify the relative humidity and temperature at which the quantity described by the standard name applies, provide scalar coordinate variables with standard names of "relative_humidity" and "air_temperature".'
We have four existing volume scattering names:
volume_scattering_function_of_radiative_flux_in_sea_water
volume_scattering_coefficient_of_radiative_flux_in_sea_water
volume_scattering_coefficient_in_air_due_to_ambient_aerosol_particles
volume_scattering_coefficient_in_air_due_to_dried_aerosol_particles.
I notice that both the sea_water ones say 'of_radiative_flux' while neither of the 'air' names do. I think it does make sense to specify what is being scattered so I suggest we modify the current proposal to:
volume_scattering_function_of_radiative_flux_in_air_due_to_ambient_aerosol_particles
and that we also create aliases for the existing in_air names:
volume_scattering_coefficient_in_air_due_to_ambient_aerosol_particles -> volume_scattering_coefficient_of_radiative_flux _in_air_due_to_ambient_aerosol_particles
volume_scattering_coefficient_in_air_due_to_dried_aerosol_particles -> volume_scattering_coefficient_of_radiative_flux_in_air_due_to_dried_aerosol_particles. Do you agree?
We have just one existing volume_scattering_function name, defined as 'The volume scattering function is the fraction of incident radiative flux scattered into unit solid angle per unit path length.'. Martin has suggested a different wording: 'The volume scattering function is the intensity (flux per unit solid angle) of scattered radiation per unit length of scattering medium, normalised by the incident radiation flux' which gives a clearer description of how the quantity is calculated. I will update the definition of the existing name to match this one.
3. integral_wrt_time_of_mole_stomatal_uptake_of_ozone (mol m-2 s-1)
This one has gone through a few iterations in the discussion. The use of 'mole_stomatal_uptake' has been agreed as this makes clear both the direction of the flux and the fact that it is a mole flux, rather than mass flux. Part way through the discussion 'integral' changed to 'integration' but I assume this was a typo - all the existing names say 'integral' so we should stick with that. I think the name itself is now agreed.
I have updated the definition to read as follows: 'The phrase "integral_wrt_X_of_Y" means int Y dX. The data variable should have an axis for X specifying the limits of the integral as bounds. The phrase "wrt" means "with respect to". The stomatal ozone uptake is the amount of ozone transferred into the plant during the time period over which the integral is calculated. This parameter is often called the "phytotoxic ozone dose (POD)". The chemical formula for ozone is O3. The IUPAC name for ozone is trioxygen.' Is this okay?
I'm not really familiar with this quantity, but if this is a time integrated dosage the units should probably be mol m-2 shouldn't they? The CMIP6 description says 'Time Integral of (hourly above canopy ozone concentration * stomatal conductance * Rc/(Rb+Rc).' According to descriptions I have been able to find of 'stomatal conductance', the units are usually mmol m?? s?? and I'm assuming 'above canopy ozone concentration' has units of mol m-3 since we're working in moles. I don't know what Rc/(Rb+Rc) represents and therefore don't know the units of that part of the formula. Please can you provide some more information about this so that we can check that the units are correct?
4. stomatal_ozone_flux_threshold (mol m-2 s-1)
This proposal has been withdrawn because the only threshold currently needed is zero. If there is a need to use other thresholds this proposal can be reintroduced.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
-----Original Message-----
From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Martin Juckes - UKRI STFC
Sent: 20 April 2018 13:33
To: Jonathan Gregory <j.m.gregory at reading.ac.uk>; cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Four standard names for the AerChemMIP data request
Sorry, that was a copying error: I accept the use of "uptake" is better,
Martin
________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Jonathan Gregory <j.m.gregory at reading.ac.uk>
Sent: 20 April 2018 13:28
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Four standard names for the AerChemMIP data request
Dear Martin
If it's OK for you as well, I'd prefer "uptake", which Michaela suggested as an alternative to "flux", because it indicates the sign convention. Or "uptake flux" if that's better - Google finds that as a phrase which is used.
Best wishes
Jonathan
----- Forwarded message from Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk> -----
> Date: Fri, 20 Apr 2018 08:41:09 +0000
> From: Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>,
> "j.m.gregory at reading.ac.uk" <j.m.gregory at reading.ac.uk>
> Subject: Re: [CF-metadata] Four standard names for the AerChemMIP data
> request
>
> Dear Jonathan, Michaela,
>
>
> I agree that "integration_wrt_time_of_mole_stomatal_flux_of_ozone" would work well.
>
>
> We have a well established general approach of indicating threshold values in a separate variable, and I would support the implication of Jonathan's remarks that, if we include the threshold, it should be done using this existing mechanism. The approach would be to append "_excess" or "_above_threshold" to the name, and in the CF metadata add a coordinate variable with standard name "stomatal_flux_of_ozone" and a data value indicating the threshold value.
>
>
> Within the data request we also have a "long name", where we have more freedom to express full details of the variable. E.g. we might modify the current long name "Phytotoxic ozone dose" to "Phytotoxic Ozone Dose above Zero Threshold".
>
>
> regards,
>
> Martin
>
>
>
> ________________________________
> From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of
> Jonathan Gregory <j.m.gregory at reading.ac.uk>
> Sent: 19 April 2018 16:26
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] Four standard names for the AerChemMIP data
> request
>
> Dear Martin and Michaela
>
> Thanks for your comments. If a non-zero threshold is sometimes used, I
> think it's a reasonable future-proofing extension that we might allow
> it here, although it's not yet been requested. I don't feel strongly
> either way. We could omit that complexity at the moment, but introduce
> the name with _excess and threshold later if required, and make the present name an alias.
>
> I think mole_stomatal_uptake_of_ozone, suggested by Michaela, would be
> good because it indicates the sign convention.
>
> Best wishes
>
> Jonathan
>
> ----- Forwarded message from Michaela Hegglin Hegglin
> <m.i.hegglin at reading.ac.uk> -----
>
> > Date: Thu, 19 Apr 2018 09:51:16 +0000
> > From: Michaela Hegglin Hegglin <m.i.hegglin at reading.ac.uk>
> > To: Martin Juckes - UKRI STFC <martin.juckes at stfc.ac.uk>
> > CC: Jonathan Gregory <j.m.gregory at reading.ac.uk>, "cf-metadata at cgd.ucar.edu"
> > <cf-metadata at cgd.ucar.edu>
> > Subject: Re: [CF-metadata] Four standard names for the AerChemMIP data
> > request
> >
> > Dear Martin, Jonathan,
> >
> > > The generic quantity that AerChemMIP is interested in, Phytotoxic ozone dose, can be used with a non-zero threshold -- so there may be a requirement for this in the future, but for CMIP6 we only need the case of threshold=0. As you point out, we can simplify the CF metadata if we restrict ourselves to this case. I'd be happy with that approach.
> >
> > To my rather modest knowledge of plant physiology, the threshold in the POD is not necessarily 0, but may be dependent on the plant type and depending on its detoxification capacity. Hence is not necessarily 0. While CMIP6 may not use the POD at other thresholds, the wider community has done so in the past and may therefore ask what threshold was used for the variable output. To me it would hence be more logical to have the threshold indicated in the name.
> >
> > > Looking at other CF names, I notice that we should be referring to the "_mole_flux_of_ozone_" rather than just the "ozone_flux" (to distinguish it from mass flux).
> >
> > Sounds like a very good idea to me too.
> >
> > > I'm not sure about the phrase "flux_into_stomata": the stomata are
> > > the holes in the leaves, what we really mean is into the plant
> > > through the stomata. I'm not sure if
> > > "integration_wrt_time_of_mole_flux_of_ozone_into_vegetation" would
> > > be specific enough;
> > > "integration_wrt_time_of_mole_flux_of_ozone_into_vegetation_throug
> > > h_stomata" looks a bit long, but may be justified for a
> > > specialised quantity like this,
> >
> > This is indeed a very long name. Is there a reason why not to simply name it after how researchers use it, namely stomatal flux or stomatal uptake? The full name could then read integration_wrt_time_of_mole_stomatal_flux_of_ozone? Whether to put in the ?into_vegetation? or ?_with_threshold_0? is possibly a matter of taste. Since only plants have stomata it should be clear that it?s meant to be vegetation, so not needed.
> >
> > Michaela
> >
> >
> >
> > >
> > > regards,
> > > Martin
> > > ________________________________
> > > From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of
> > > Jonathan Gregory <j.m.gregory at reading.ac.uk>
> > > Sent: 18 April 2018 17:41
> > > To: cf-metadata at cgd.ucar.edu
> > > Subject: [CF-metadata] Four standard names for the AerChemMIP data
> > > request
> > >
> > > Dear Martin
> > >
> > >> Proposed name: integral_wrt_time_of_stomatal_ozone_flux_excess
> > >
> > > I appreciate that not all fluxes have their sign convention
> > > mentioned in the name, but in the case of precipitation, for
> > > example, I think it's obvious - that's not quite so with
> > > ozone_flux, I would say - on reflection, I guess that plants don't
> > > ever produce ozone, so the flux should be into the stomata, but
> > > although it can be clarified in the definition, as you say, I feel
> > > it would be even better to choose a word in the standard name which indicates which way the flux is going e.g. flux_into_stomata.
> > >
> > > There are existing names containing mole_flux_of_SPECIES. This is
> > > one of those so it might be good to follow that pattern too.
> > >
> > > I see that pod0 has a threshold of zero. You're proposing
> > > something more general, which could support any threshold, but is
> > > the threshold ever going to be non-zero? If zero is the only
> > > possibility, it doesn't need to be described as an excess.
> > >
> > >> (3b) stomatal_ozone_flux_threshold [mol m-2 s-1]
> > >>
> > >> A standard name to be used on variable specifying a threshold value of stomatal ozone flux.
> > >
> > > This quantity would be more generally useful if "threshold" was
> > > omitted. I'm aware there is an air_temperature_threshold in the
> > > table, but I see no reason why a quantity used as a threshold must have "threshold" in its name.
> > >
> > > Best wishes and thanks
> > >
> > > Jonathan
> > > _______________________________________________
> > > CF-metadata mailing list
> > > CF-metadata at cgd.ucar.edu
> > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> >
>
> ----- End forwarded message -----
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Received on Wed May 02 2018 - 12:47:52 BST
