Thanks Jonathon, Of the below "elevation_of_sea_surface_due_to_X" sounds most appropriate.
But sticking with the previously suggested sea_surface_elevation theme and noting that tides, surges and waves can also occur in large inland water bodies such as the Great Lakes, how about using the more generic phrase: water_surface_elevation_due_to_X This would remove the tie back to a given datum, as per John's point, and a set of "due_to_X"s could be neatly combined with a reference level in order to construct "water_surface_height_above_reference_datum" if so desired. Does that make sense? Andy -----Original Message----- From: CF-metadata [mailto:[email protected]] On Behalf Of Jonathan Gregory Sent: 24 April 2018 14:26 To: [email protected] Subject: [CF-metadata] Fwd: Re: proposed new standard name for storm surge residual Dear Andrew and John I hadn't noticed that sea_surface_elevation is already in use as an alias. That's a pity, but maybe it would be confusing anyway, given John's comment. I think that what Andrew needs is terms that say how much higher the sea surface is because of influence X relative to how high it would be in the absence of influence X. Such terms do not need any datum (like geoid or MSL). The difference in z is the same regardless of what datum would be used for z itself. I suggested before that change_in would be a possibility but it doesn't sound quite right, because we aren't comparing SSH before and after a storm surge for example, which is what I'd understand by "change in SSH due to storm surge". Other ideas: elevation_of_sea_surface_due_to_X increment_to_sea_surface_height_due_to_X increase_of_sea_surface_height_due_to_X What others occur to you? Best wishes Jonathan ----- Forwarded message from "Saulter, Andrew" <[email protected]> ----- > Date: Tue, 24 Apr 2018 07:17:48 +0000 > From: "Saulter, Andrew" <[email protected]> > To: "[email protected]" <[email protected]> > Subject: Re: [CF-metadata] proposed new standard name for storm surge > residual > > John, > > I see where you are with that, but my understanding from Jonathon Gregory's > email earlier is that the 'due_to' part of the phrasing identifies a > component process that contributes to an overall quantity. In the case below > 'due_to_storm_surge' is a contribution to 'sea_surface_elevation' and that > quantity is what needs to be referenced to some datum. Or maybe I'm not > getting it? Steep learning curve this... > > Anyway, having thought about datum's now I have done some further searching > and noted the following already exist as standard names: > > water_surface_height_above_reference_datum - this denotes the quantity > > water_surface_reference_datum_altitude - references the datum to the > (grid_mapping) geoid > > These look much more like what I was after, so the question is can the > 'due_to_storm_surge' and 'due_to_tide' be sensibly appended to > 'water_surface_height_above_reference_datum'?? > > Cheers > Andy > > > -----Original Message----- > From: John Graybeal [mailto:[email protected]] > Sent: 23 April 2018 17:57 > To: Saulter, Andrew <[email protected]> > Cc: CF Metadata List <[email protected]> > Subject: Re: [CF-metadata] proposed new standard name for storm surge > residual > > > I actually find this new name/definition internally inconsistent. An > elevation that is ‘due to storm surge’ seems to be relative to the > elevation without the storm surge, which makes the datum irrelevant. > Unless the change due to the storm surge would be measured differently > under different datums, but I can’t imagine that. (Taking the other > way, if it’s an elevation relative to some normal datum, then “due to > storm surge” is irrelevant.) > > In any case, under the new definition, the description needs to include > exactly how the datum is specified. The computers and people will need to > know where to look for that information, and ideally it should be a unique > identifier that the computers can recognize and understand. > > > john > > > > On Apr 23, 2018, at 01:43, Saulter, Andrew > > <[email protected]> wrote: > > > > Apologies, a little bit more to add to the below following up from > > Jonathon's first email, > > > > For both tide and surge I would actually prefer to go with Jonathon's > > suggestion that the 'height_above_mean_sea_level' part of my suggestions is > > replaced with 'elevation'. This is a much more compact and flexible way of > > expressing things and means, particularly with tide that we can reference > > this to whichever datum we like (for example Chart Datum, Ordnance Datum, > > MSL) dependent on source elsewhere in the metadata. I think it is also > > appropriate that we think of "sea_surface_elevation" as a quantity that can > > be contributed to via processes with many different timescales, e.g. tides, > > surges, individual ocean waves. > > > > This would take us to: > > > > Proposed standard name: > > sea_surface_elevation_due_to_storm_surge > > Units: m > > "Sea surface elevation" is a time-varying quantity denoting the height of > > the sea surface relative to a given datum. 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. Storm surge effects, due to meteorological > > forcing of the ocean and interaction between the generated surge and tides, > > are a significant contributor to the observed sea surface height. > > > > Proposed standard name: > > sea_surface_elevation_due_to_tide > > Units: m > > "Sea surface elevation" is a time-varying quantity denoting the height of > > the sea surface relative to a given datum. 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. Tides are a significant contributor to the > > observed sea surface height; here “tide” denotes a generic variable > > describing the time varying tidal signal, for example as generated based on > > a summation of harmonically analysed components, or resulting from the > > application of such components as boundary conditions to a numerical tidal > > model. > > > > However, I have one concern in that "sea_surface_elevation" is presently > > given as an alias for "sea_surface_height_above_geoid". My worry is that > > the latter has implications for the vertical datum and that we might choose > > to disconnect this from other aspects of the grid_mapping variable (e.g. > > where my station positions are in WGS84, but the vertical reference is to > > chart datum) in which case we are not strictly referencing against the > > geoid any more. In addition, the term "sea_surface_height" has more usually > > been associated with altimeter and model products where high frequency > > signals are generally excluded? > > > > So some consensus as to whether "sea_surface_elevation" is the phrasing to > > go for would be very helpful... > > > > Cheers > > Andy > > > > -----Original Message----- > > From: CF-metadata [mailto:[email protected]] On > > Behalf Of Saulter, Andrew > > Sent: 20 April 2018 17:04 > > To: [email protected] > > Subject: Re: [CF-metadata] proposed new standard name for storm > > surge residual > > > > Jonathon, Helen, > > > > Thanks for the feedback. > > > > I'd looked at the existing 'sea_surface_height' terms but had the same > > worry as Jonathon that the use of 'amplitude' restricted these to some > > (unspecified) time integral. What I'm after is definitely a variable that > > varies as a function of time. It's also unusual in the coastal forecasting > > community to want to split the various contributions to tide up. > > > > The 'due_to_air_pressure_and_wind' term captures the primary meteorological > > processes that induce surge. However, these do not capture the effect of > > tide-surge interaction in shallower waters (for example the extra surge > > elevation enhances the speed at which the tide propagates so a 'surge > > residual' can include the propagation speed delta as well as the background > > super-elevation) nor other secondary variability that we often see in surge > > residuals, such as steric changes of the water column. So I feel that using > > a catchall term 'storm_surge', although less specific would have a lot less > > potential to mislead a user. The option exists, I assume, in the comments > > attribute for a variable to be more precise about its derivation/generating > > processes. > > > > So overall, I couldn't find a goldilocks term for either surge or tide that > > would fit my users understanding of the variables - hence the new > > suggestions. > > > > Have a good weekend > > Andy > > > > > > > > -----Original Message----- > > From: CF-metadata [mailto:[email protected]] On > > Behalf Of Jonathan Gregory > > Sent: 11 April 2018 18:37 > > To: [email protected] > > Subject: [CF-metadata] proposed new standard name for storm surge > > residual > > > > Dear Helen and Andy > > > > I noticed the sea_surface_height_amplitude_due_to_X_tide names as well, and > > I wondered, what does "amplitude" mean here? The definitions of these names > > don't say, and I feel that we should be clear. I guessed it might mean the > > amplitude of SSH due to the tidal cycle, whereas I think Andy means the > > actual tidal height as a function of time. Are you able to clarify? > > > > It's a good point about due_to_air_pressure[_and_wind], thanks. That may > > not obviously mean "storm surge", which maybe could be inserted in the > > definition. > > > > Best wishes > > > > Jonathan > > > > ----- Forwarded message from "Snaith, Helen M." > > <[email protected]> > > ----- > > > >> Date: Tue, 10 Apr 2018 13:14:16 +0000 > >> From: "Snaith, Helen M." <[email protected]> > >> To: "Saulter, Andrew" <[email protected]> > >> CC: "[email protected]" <[email protected]> > >> Subject: Re: [CF-metadata] proposed new standard name for storm surge > >> residual > >> x-mailer: Apple Mail (2.3445.6.18) > >> > >> Hi Andy > >> > >> Many of the sea_surface_height terms have been used in satellite altimetry > >> for some time. > >> The tidal components have been split out into > >> sea_surface_height_amplitude_due_to_equilibrium_ocean_tide<javascript: > >> void(0)> > >> sea_surface_height_amplitude_due_to_geocentric_ocean_tide<javascript: > >> v > >> oid(0)> > >> sea_surface_height_amplitude_due_to_non_equilibrium_ocean_tide<java > >> sc > >> r > >> ipt:void(0)> > >> > >> And the pole tide > >> sea_surface_height_amplitude_due_to_pole_tide<javascript:void(0)> > >> > >> In these terms, amplitude has been used to identify the ‘above mean > >> level’ and sea_surface_height is as alias of > >> sea_surface_heigth_above_mean_sea_level > >> > >> > >> Also included are the terms > >> sea_surface_height_correction_due_to_air_pressure_and_wind_at_high_ > >> fr > >> e > >> quency<javascript:void(0)> > >> sea_surface_height_correction_due_to_air_pressure_at_low_frequency< > >> ja > >> v > >> ascript:void(0)> > >> > >> The former of which is related to surge I think - it is normally > >> determined from a tidal model and is the response of sea level to changes > >> in air pressure and wind. > >> > >> Even if these are not the correct terms, as you are not determining a > >> 'correction’ but a value - they should be related to the surge components, > >> so do they give the ‘due to’ component you need? > >> > >> Helen > >> > >> > >> On 4 Apr 2018, at 17:13, Saulter, Andrew > >> <[email protected]<mailto:[email protected]>> > >> wrote: > >> > >> Dear all, > >> > >> First posting to this list, so please forgive me if I’m doing it > >> wrong… > >> > >> I’d like to request an addition to the standard name list to include storm > >> surge residual and tide. These variables are generated for the purpose of > >> coastal flood prediction and will be available in future, netCDF based, > >> operational products from the Met Office. > >> > >> Proposed standard name: > >> sea_surface_height_above_mean_sea_level_due_to_storm_surge > >> Units: m > >> "Sea surface height" is a time-varying quantity. "Height_above_X" means > >> the vertical distance above the named surface X. "Mean sea level" means > >> the time mean of sea surface elevation at a given location over an > >> arbitrary period sufficient to eliminate the tidal signals. 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. Storm surge > >> effects, due to meteorological forcing of the ocean and interaction > >> between the generated surge and tides, are a significant contributor to > >> the observed sea surface height. > >> > >> Proposed standard name: > >> sea_surface_height_above_mean_sea_level_due_to_tide > >> Units: m > >> "Sea surface height" is a time-varying quantity. "Height_above_X" means > >> the vertical distance above the named surface X. "Mean sea level" means > >> the time mean of sea surface elevation at a given location over an > >> arbitrary period sufficient to eliminate the tidal signals. 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. Tides are a > >> significant contributor to the observed sea surface height; here “tide” > >> denotes a generic variable describing the time varying tidal signal, for > >> example as generated based on a summation of harmonically analysed > >> components, or resulting from the application of such components as > >> boundary conditions to a numerical tidal model. > >> > >> Many thanks > >> Andy > >> > >> > >> Andy Saulter > >> Surge, Waves and Metocean Projects Manager Met Office FitzRoy Road > >> Exeter Devon EX1 3PB > >> Tel: +44 (0)1392 884703 Fax: +44 (0)1392 885681 > >> [email protected]<mailto:[email protected] > >> .u > >> k > >>> http://www.metoffice.gov.uk<http://www.metoffice.gov.uk/> > >> > >> > >> -- > >> This message has been scanned for viruses and dangerous content by > >> MailScanner<http://www.mailscanner.info/>, and is believed to be > >> clean. _______________________________________________ > >> CF-metadata mailing list > >> [email protected]<mailto:[email protected]> > >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > >> > >> ________________________________ > >> This message (and any attachments) is for the recipient only. 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