Dear Martin I agree with your suggestions and clarifications. It would be good to keep "heat content" because it is widely understood (in the sense that we use it, J m-2). I agree that "content" implies the amount of something per unit area integrated over the vertical extent of something else. It's not used only for mass content; we have a lot of energy content names too e.g. thermal_energy_content_of_surface_snow and this last one suggests that maybe we could say "thermal energy" instead of "sensible heat" in the name about rainfall temperature? (Sorry - that is a hideous confusing of email threads by me.) In addition, we have enthalpy, mole, number and radioactivity content names, all with the same sense.
Best wishes Jonathan ----- Forwarded message from Martin Juckes - UKRI STFC <[email protected]> ----- > Date: Mon, 25 Jun 2018 13:06:26 +0000 > From: Martin Juckes - UKRI STFC <[email protected]> > To: "[email protected]" <[email protected]>, > "[email protected]" <[email protected]> > Subject: Re: [CF-metadata] > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content > units > > Hello Jonathan, > > > I agree that the "integral_wrt_depth_" is a little surprising here, but I > think it is better than saying temperature when we mean "temperature times > thickness". > > > In any case, we have a term: > > tendency_of_sea_water_potential_temperature_expressed_as_heat_content > > which is intended to be the tendency of > integral_wrt_depth_of_sea_water_potential_temperature_expressed_as_heat_content, > which doesn't look right. There should be consistency here -- either include > "integral_wrt_depth_" in both cases, or exclude it in both cases. > > > When dealing with mass, the use of "content" in a standard name automatically > implies a vertical integral, so we might get away without stating it > explicitly here, but it is a slightly different usage. The current help text > includes the remark that '"Content" indicates a quantity per unit area.', > which I find a little cryptic: perhaps it could be expanded to : '"Content" > indicates a quantity per unit area, integrated over height or depth.' > > > The text explaining "expressed_as_heat_content" could also be adjusted > (currently: 'The phrase "expressed_as_heat_content" means that this quantity > is calculated as the specific heat capacity times density of sea water > multiplied by the conservative temperature of the sea water in the grid > cell') to refer to the multiplication by thickness. > "expressed_as_heat_content" is only used with sea water potential temperature > and conservative temperature. E.g. > > 'The phrase "expressed_as_heat_content" means that this quantity is > calculated as the specific heat capacity times density of sea water > multiplied by the conservative temperature of the sea water in the grid cell > and integrated over depth. If used for a layer heat content, coordinate > bounds should be used to define the extent of the layers'. > > With these modifications, I think we could justify staying with > > tendency_of_sea_water_potential/conservative_temperature_expressed_as_heat_content > and dropping the "integral _wrt_depth_" from > > integral_wrt_depth_of_sea_water_potential_temperature_expressed_as_heat_content > and integral_wrt_depth_of_sea_ice_temperature_expressed_as_heat_content > (these are the only two terms which combine integral_wrt_depth and > expressed_as_heat_content). > > regards, > Martin > > > > > > ________________________________ > From: CF-metadata <[email protected]> on behalf of Jonathan > Gregory <[email protected]> > Sent: 25 June 2018 10:57 > To: [email protected] > Subject: Re: [CF-metadata] > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content units > > Dear Alison and Steve > > I suggest that we can be more relaxed about units for X_expressed_as_Y, so > that > X and Y don't have to be dimensionally equivalent. We can express the change > in > temperature of an ocean layer as a change in heat content by using the heat > capacity - that's the idea of these names, and similarly for the names with > tendency_of_sea_water_salinity_expressed_as_salt_content, which have the units > (kg m-2 s-1) expected for a tendency in salt content, not a tendency in > salinity (which would be s-1). It's useful to mention temperature (rather than > heat content) because it allows us to specify whether we mean potential or > conservative temperature. > > I agree that we could insert integral_wrt_depth_of, for both set of names. > However this seems a bit surprising since the names are generally for 3D > quantities. Each cell applies to one ocean layer. The "integral" is just the > cell value multiplied by the cell thickness. > > Best wishes > > Jonathan > > ----- Forwarded message from Alison Pamment - UKRI STFC > <[email protected]> ----- > > > Date: Mon, 25 Jun 2018 09:28:28 +0000 > > From: Alison Pamment - UKRI STFC <[email protected]> > > To: Stephen Griffies - NOAA Federal <[email protected]> > > CC: Martin Juckes - UKRI STFC <[email protected]>, > > "[email protected]" <[email protected]>, Jonathan > > Gregory <[email protected]>, Karl Taylor <[email protected]>, > > "Durack, Paul J." <[email protected]> > > Subject: Re: > > > > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content > > units > > > > Dear Stephen, > > > > Thank you for getting back to me. > > > > A CF standard name for integral_wrt_depth need not necessarily be > > interpreted as a full ocean depth quantity. The limits of the integral are > > specified by placing bounds on the vertical coordinate variablle that is > > attached to the data variable. The bounds can be used to indicate that an > > integral has been calculated over a single model layer, for example. We > > recently discussed on the mailing list how to specify the limits if the > > integral is calculated over the whole ocean depth and it was agreed that if > > no limits (i.e. bounds) are specified then the integral is assumed to be > > full depth. This clarification has now been added to the definitions of all > > the integral_ wrt_depth standard names. > > > > I think Martin's question regarding the units is an important one and it > > would be better to be clear in the names that the quantities are vertical > > integrals if that is indeed the case. The bounds can then be used to > > describe the limits, as above. I think it would then be okay to describe > > something as being the tendency of an integrated quantity. My own question > > related to the order in which the operations are carried out on the > > variable, I.e. is it the tendency of the vertical integral, or the vertical > > integral of the tendency? > > > > Best wishes, > > Alison > > ________________________________ > > From: Stephen Griffies - NOAA Federal <[email protected]> > > Sent: 21 June 2018 14:00:46 > > To: Pamment, Alison (STFC,RAL,RALSP) > > Cc: Juckes, Martin (STFC,RAL,RALSP); [email protected]; Jonathan > > Gregory; Karl Taylor; Durack, Paul J. > > Subject: Re: > > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content > > units > > > > Alison, > > > > Thanks for staying on top of these matters. > > > > The diagnostics "tendency_of_sea_water_" refer to the tendency as > > integrated over the thickness of a single model grid cell. > > > > In contrast, > > "integral_wrt_depth_of_sea_ice_temperature_expressed_as_heat_content " is > > an integral over the full ocean depth from bottom to top. > > > > I recommend we keep the naming convention unchanged in order to clearly > > distinguish between the two diagnostics. > > > > Stephen > > > > > > > > > > > > On Thu, Jun 21, 2018 at 2:42 AM, Alison Pamment - UKRI STFC > > <[email protected]<mailto:[email protected]>> wrote: > > Dear Martin, Stephen and Jonathan, > > > > We have seven existing > > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content > > names (and seven existing > > tendency_of_sea_water_potential_temperature_expressed_as_heat_content > > names)all with units of W m-2. I think all of these were introduced for > > OMIP. > > > > If something is described as a 'heat content' I would expect it to have > > units of J m-2. Indeed that is the case for the two existing names > > integral_wrt_depth_of_sea_ice_temperature_expressed_as_heat_content and > > integral_wrt_depth_of_sea_water_potential_temperature_expressed_as_heat_content. > > Calculating tendencies of such quantities would then give us units of W > > m-2. This suggests to me that the OMIP names should all follow the pattern: > > tendency_of_integral_wrt_depth_of_sea_water_X_temperature_expressed_as_heat_content > > where X is 'potential' or 'conservative'. The bounds of the vertical > > coordinate variable should give the limits on the integral for each grid > > cell. > > > > Does this pattern of writing the names match the method of calculating the > > quantities (i.e. the tendency of the integral, rather than the integral of > > the tendency?) > > > > We can of course create aliases to correct the names once we have agreed on > > what changes are needed. > > > > Best wishes, > > Alison > > > > ------ > > Alison Pamment Tel: +44 1235 778065 > > NCAS/Centre for Environmental Data Archival Email: > > [email protected]<mailto:[email protected]> > > STFC Rutherford Appleton Laboratory > > R25, 2.22 > > Harwell Oxford, Didcot, OX11 0QX, U.K. > > > > From: Juckes, Martin (STFC,RAL,RALSP) > > Sent: 10 June 2018 18:52 > > To: Stephen Griffies - NOAA Federal > > <[email protected]<mailto:[email protected]>> > > Cc: [email protected]<mailto:[email protected]>; Jonathan > > Gregory <[email protected]<mailto:[email protected]>>; Karl > > Taylor <[email protected]<mailto:[email protected]>>; Pamment, Alison > > (STFC,RAL,RALSP) > > <[email protected]<mailto:[email protected]>>; Durack, Paul > > J. <[email protected]<mailto:[email protected]>> > > Subject: Re: > > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content > > units > > > > Hi Stephen, > > > > thanks, that is clear. There may be an issue with the CF standard name ... > > we usually have "integral_wrt_depth" in the name for such quantities. > > Perhaps Jonathan or Alison can comment on that, > > > > regards, > > Martin > > > > ________________________________________ > > From: Stephen Griffies - NOAA Federal > > <mailto:[email protected]<mailto:[email protected]>> > > Sent: 10 June 2018 16:52 > > To: Juckes, Martin (STFC,RAL,RALSP) > > Cc: mailto:[email protected]<mailto:[email protected]>; > > Jonathan Gregory; Karl Taylor; Pamment, Alison (STFC,RAL,RALSP); Durack, > > Paul J. > > Subject: Re: > > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content > > units > > > > Hi, > > > > Thanks for the question. > > > > As discussed in Griffies et al (2016), we request heat and salt budgets to > > be integrated over the thickness of a grid cell. For the heat budget, this > > thickness weighting then leads to units of W m-2 rather than W m-3. > > > > There is a good reason to ask for the diagnosed budgets to be integrated > > over the thickness of a grid cell. Namely, most ocean models have > > time-dependent grid cell thicknesses. So the only way to ensure budgets can > > be closed with offline diagnostics is to have each model perform the > > thickness weighting online. > > > > Make sense? > > > > Best, > > Stephen > > > > > > > > On Sun, Jun 10, 2018 at 9:58 AM, Martin Juckes - UKRI STFC > > <mailto:[email protected]<mailto:[email protected]>> wrote: > > Dear Jonathan, Stephen, Karl, > > > > > > I'm puzzled by the units of the CMIP6 variable ocontemptend and teh > > associated standard name > > tendency_of_sea_water_conservative_temperature_expressed_as_heat_content > > -- in the data request and the standard name table respectively with units > > "W m-2". This is consistent with the Griffies et al 2016 paper on ocean > > diagnostics and with the discussion on the CF mailing list. However, it is > > requested as a function of depth, so I would expect to see units of "W m-3" > > for the tendency of a heat density. > > > > > > The units "W m-2" are usually used for a surface heat flux. There are a > > number of variables related to ocontemptend with the same units. > > > > > > Am I missing something, or should we change the units or the depth > > dependency? > > > > > > regards, > > > > Martin > > > > > > > > > > > > -- > > Dr. Stephen M. Griffies > > NOAA Geophysical Fluid Dynamics Lab > > 201 Forrestal Road > > Princeton, NJ 08542 > > USA > > > > > > > > > > -- > > Dr. Stephen M. Griffies > > NOAA Geophysical Fluid Dynamics Lab > > 201 Forrestal Road > > Princeton, NJ 08542 > > USA > > > > ----- 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
