Hello Andrew,
I've been watching this thread without responding. Your request in this e-mail makes a lot of sense to me.
Cheers, Roy.
Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquiries at bodc.ac.uk. Please also use this e-mail if your requirement is urgent.
________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Saulter, Andrew <andrew.saulter at metoffice.gov.uk>
Sent: 24 April 2018 08:17
To: cf-metadata at cgd.ucar.edu
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:jbgraybeal at mindspring.com]
Sent: 23 April 2018 17:57
To: Saulter, Andrew <andrew.saulter at metoffice.gov.uk>
Cc: CF Metadata List <cf-metadata at cgd.ucar.edu>
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 <andrew.saulter at metoffice.gov.uk> 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:cf-metadata-bounces at cgd.ucar.edu] On Behalf
> Of Saulter, Andrew
> Sent: 20 April 2018 17:04
> To: cf-metadata at cgd.ucar.edu
> 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:cf-metadata-bounces at cgd.ucar.edu] On Behalf
> Of Jonathan Gregory
> Sent: 11 April 2018 18:37
> To: cf-metadata at cgd.ucar.edu
> 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." <h.snaith at bodc.ac.uk>
> -----
>
>> Date: Tue, 10 Apr 2018 13:14:16 +0000
>> From: "Snaith, Helen M." <h.snaith at bodc.ac.uk>
>> To: "Saulter, Andrew" <andrew.saulter at metoffice.gov.uk>
>> CC: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
>> 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<javasc
>> 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 <andrew.saulter at metoffice.gov.uk<mailto:andrew.saulter at metoffice.gov.uk>> 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
>> andrew.saulter at metoffice.gov.uk<mailto:andrew.saulter at metoffice.gov.u
>> k
>>> http://www.metoffice.gov.uk<http://www.metoffice.gov.uk/>
>>
>>
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