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
