Dear Jonathan, Thank you. I think these changes are all agreed now. I will include them in today's standard name table update.
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: Jonathan Gregory <[email protected]> Sent: 01 July 2018 18:29 To: Pamment, Alison (STFC,RAL,RALSP) <[email protected]> Subject: Re: [CF-metadata] tendency_of_sea_water_conservative_temperature_expressed_as_heat_content units Dear Alison Yes, this looks fine to me, thanks. I like the simplification for consistency. Best wishes Jonathan On Thu, Jun 28, 2018 at 03:28:14PM +0000, Alison Pamment - UKRI STFC wrote: > Date: Thu, 28 Jun 2018 15:28:14 +0000 > From: Alison Pamment - UKRI STFC <[email protected]> > To: "[email protected]" <[email protected]>, "Jonathan > Gregory ([email protected])" <[email protected]> > Subject: RE: [CF-metadata] > > tendency_of_sea_water_conservative_temperature_expressed_as_heat_conte > nt > units > > Dear Jonathan, Martin and Stephen, > > Thank you all for your comments on these names. > > I think what we have agreed to keep the fourteen existing > tendency_of_sea_water_X_temperature_expressed_as_heat_content[_due_to_Y] > names as they are. (X is 'conservative' or 'potential' and Y is a process > name). > > I agree that we should amend the definitions along the lines Martin suggests. > I think that for these names we could completely remove the sentence ' > "Content" indicates a quantity per unit area' because it's not really > necessary. Then we could amend the heat content text to read as follows: > '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|potential] 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. If no > coordinate bounds are specified, it is assumed that the integral is > calculated over the entire vertical extent of the medium, e.g, if the medium > is sea water the integral is assumed to be calculated over the full depth of > the ocean.' > This would be consistent with the text we recently agreed for > 'integral_wrt_depth|height' names. I have written out one name in full so > that we have an example: > tendency_of_sea_water_potential_temperature_expressed_as_heat_content > 'The phrase "tendency_of_X" means derivative of X with respect to time. This > tendency encompasses all processes that impact on the time changes for the > heat content within a grid cell. 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 potential 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. If no > coordinate bounds are specified, it is assumed that the integral is > calculated over the entire vertical extent of the medium, e.g, if the medium > is sea water the integral is assumed to be calculated over the full depth of > the ocean. Potential temperature is the temperature a parcel of air or sea > water would have if moved adiabatically to sea level pressure.' > > Okay? > > I think we have agreed to create the following aliases: > integral_wrt_depth_of_sea_water_potential_temperature_expressed_as_hea > t_content -> sea_water_potential_temperature_expressed_as_heat_content > integral_wrt_depth_of_sea_ice_temperature_expressed_as_heat_content -> > sea_ice_temperature_expressed_as_heat_content > The text explaining 'integral_wrt_depth' would be removed from the > definitions and the amended 'expressed_as_heat_content' would take its place. > > Okay? > > 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 <[email protected]> On Behalf Of > Jonathan Gregory > Sent: 25 June 2018 19:06 > To: [email protected] > Subject: Re: [CF-metadata] > tendency_of_sea_water_conservative_temperature_expressed_as_heat_conte > nt units > > 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_con > > te > > nt > > 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_conten > > t > > > > 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_a > > s_ 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_con > > te > > nt 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_c > > > on > > > tent 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_expresse > > > d_ 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_c > > > on > > > tent 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_c > > > on > > > tent 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 > _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
