Hello Michael,
I'm slightly puzzled by the reference to the growing season: the variable pod0 is currently requested to be provided as monthly values, which would imply that the integral wrt time has to be taken over a calendar month. The variable would then indicate the mol m-2 of ozone uptake through stomata in each month, and the user will need to combine the values to make up a growing season (which would presumably be different time periods in different locations). Does this make sense, or do we need to change the monthly time period? regards, Martin ________________________________ From: Michael Schulz <[email protected]> Sent: 02 May 2018 20:32 To: Juckes, Martin (STFC,RAL,RALSP) Cc: Pamment, Alison (STFC,RAL,RALSP); Michaela Hegglin; [email protected]; Jonathan Gregory Subject: Re: [CF-metadata] Four standard names for the AerChemMIP data request Hi, see here for the definition of phytotoxic ozone doses: PODy http://www.emep.int/mscw/definitions.pdf The problem is that its the accumulated flux over the growing season, so its "per vegetation year”. Unit "mol m-2” is thus correct but has an implicit time in it, the length of the growing season. hope this helps, Michael > On 2 May 2018, at 20:47, Martin Juckes - UKRI STFC <[email protected]> > wrote: > > 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; > [email protected] > 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_aerosol" 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⁻² s⁻¹ > 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: > [email protected] > STFC Rutherford Appleton Laboratory > R25, 2.22 > Harwell Oxford, Didcot, OX11 0QX, U.K. > > -----Original Message----- > From: CF-metadata [mailto:[email protected]] On Behalf Of > Martin Juckes - UKRI STFC > Sent: 20 April 2018 13:33 > To: Jonathan Gregory <[email protected]>; [email protected] > 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 <[email protected]> on behalf of Jonathan > Gregory <[email protected]> > Sent: 20 April 2018 13:28 > To: [email protected] > 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 > <[email protected]> ----- > >> Date: Fri, 20 Apr 2018 08:41:09 +0000 >> From: Martin Juckes - UKRI STFC <[email protected]> >> To: "[email protected]" <[email protected]>, >> "[email protected]" <[email protected]> >> 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 <[email protected]> on behalf of >> Jonathan Gregory <[email protected]> >> Sent: 19 April 2018 16:26 >> To: [email protected] >> 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 >> <[email protected]> ----- >> >>> Date: Thu, 19 Apr 2018 09:51:16 +0000 >>> From: Michaela Hegglin Hegglin <[email protected]> >>> To: Martin Juckes - UKRI STFC <[email protected]> >>> CC: Jonathan Gregory <[email protected]>, "[email protected]" >>> <[email protected]> >>> 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 <[email protected]> on behalf of >>>> Jonathan Gregory <[email protected]> >>>> Sent: 18 April 2018 17:41 >>>> To: [email protected] >>>> 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 >>>> [email protected] >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>> >> >> ----- End forwarded message ----- >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > ----- End forwarded message ----- > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
