Hello Roy.
Essentially we are dealing with two types of data:
1.) water level time series for individual locations, e. g. at tidal gauge
stations; and
2.) water level time series computed by numerical models working on unstructured
orthogonal grids,
where water level is e. g. computed for each face (polygon) of the
computational grid.
>From the above data we derive tidal quantities, e. g. (tidal) high water. This
means that for
- each (measured) time serie at a tidal gauge station, or
- each (computed) time serie at a face (polygon) of the computational grid
we are computing all (tidal) high waters as well as all times of (tidal) high
water.
For one tidal gauge we then typically obtain nHW high waters for a time serie.
We may find
one, two or even four high waters per day. The data which are stored in this
situation are
- time coordinate : nHW(nHW) with time of occurrence for high waters HW, and
- high water level : HW(nHW) with the actual high water value.
For results from a numerical model we are actually proceeding as follows:
- compute nHW(nHW) for a so called "reference location", where no drying
and wetting takes place, and all water level maxima are present
- subsequently compute
. high water level : HW(nHW,nFace) for all computational faces nFace
(polygons), with _FillValue
used in case HW does not occur due to e. g. drying
in the intertidal zone
. time difference : dtHW(nHW,nFace), which is the time difference for the
occurence of high water
for any face (polygon) in comparison with the
"reference location"; the latter is
just a specific face (polygon) within the
computational grid.
In this case times given for the "reference location".
Alternatively one might also make use of an auxiliary time coordinate
auxHW(nHW,nFace).
- after all HW values were computed, we then derive the maximum, minimum and
mean
HW for all faces (polygons) .
As an example I would like to refer to our BAWiki page
http://www.baw.de/methoden_en/index.php5/Example_figures:_High_water
where you can find visualizations of a high water for a specific tide, as well
as maximum,
minimum and mean high water for a longer period of time.
I hope that this information will answer your question at least to some extent.
G?nther
> "Lowry, Roy K." <rkl at bodc.ac.uk> hat am 4. Juni 2014 um 17:53 geschrieben:
>
>
> Hello Guenther,
>
>
>
> There is a lot here and so far I have just had time to look at your first
> proposed Standard Name. What I don't understand is the time context of your
> data. There are two high tides per day (or even four in places like the
> Solent), each of which has a different high water level and of course these
> differ from day to day due to spring-neap cycles. To what period of time does
> tidal_high_water_above_sea_level refer?
>
>
>
> Maybe if you explained a little about the type of data you are trying to
> encode into CF I might understand a little better.
>
>
>
> Cheers, Roy.
>
>
>
>
>
> Please note that I now work part-time from Tuesday to Thursday. E-mail
> response on other days is possible but not guaranteed!
>
>
>
> From: "Lang, G?nther" [mailto:guenther.lang at baw.de]
> Sent: 04 June 2014 13:51
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] new standard names : tidal quantities
> tidal_high_water, ...
>
>
>
> Preface
>
> It is suggested to introduce new standard names for several tidal
> quantities like (tidal) high_water, low_water etc. These are geophysical
> concepts and it would be not adequate to describe them with cell_methods
> and/or time bounds.
>
> ---
> 1.) tidal_high_water_level_above_sea_level [ m ]
>
> The maximum height reached by a rising tide. The high water is due
> to the periodic tidal forces and the effects of meteorological,
> hydrologic, and/or oceanographic conditions. Sea_level means mean
> sea level, which is close to the geoid in sea areas.
>
>
> ---
> 2.) tidal_low_water_level_above_sea_level [ m ]
>
> The minimum height reached by a falling tide. The low water is due
> to the periodic tidal forces and the effects of meteorological,
> hydrologic, and/or oceanographic conditions. Sea_level means mean
> sea level, which is close to the geoid in sea areas.
>
>
> ---
> 3.) tidal_range [ m ]
>
> Arithmetic mean between tidal rise and tidal fall. Due to the periodic
> tidal forces and the effects of meteorological, hydrologic, and/or
> oceanographic conditions.
>
>
> ---
> 4.) half_tide_level_above_sea_level [ m ]
>
> Water level at half tidal range. The level midway between high
> water and mean low water for a tide. Due to the periodic tidal
> forces and the effects of meteorological, hydrologic, and/or
> oceanographic conditions. Sea_level means mean sea level, which is
> close to the geoid in sea areas.
>
>
> ---
> 5.) mean_tide_water_level_above_sea_level [ m ]
>
> The mean surface elevation as determined by averaging the heights
> of the water at equal intervals of time for a tidal period, which is
> the interval between two successive low waters. Differs
> from half tide level due to tidal asymmetry. Due to the periodic tidal
> forces and the effects of meteorological, hydrologic, and/or
> oceanographic conditions. Sea_level means mean sea level, which is
> close to the geoid in sea areas.
>
>
> ---
> 6.) mean_tidal_rise_water_level_above_sea_level [ m ]
> (opt) mean_flood_water_level_above_sea_level [ m]
>
> The mean surface elevation as determined by averaging the heights
> of the water at equal intervals of time for the period of tidal rise,
> which is the interval from low water to high water.
> Differs from mean water level during tidal fall due to tidal
> asymmetry. Due to the periodic tidal forces and the effects of
> meteorological, hydrologic, and/or oceanographic conditions.
> Sea_level means mean sea level, which is close to the geoid in
> sea areas.
>
>
> ---
> 7.) mean_tidal_fall_water_level_above_sea_level [ m ]
> (opt) mean_ebb_water_level_above_sea_level [ m]
>
> The mean surface elevation as determined by averaging the heights
> of the water at equal intervals of time for the period of tidal fall,
> which is the interval from high water to low water.
> Differs from mean water level during tidal rise due to tidal
> asymmetry. Due to the periodic tidal forces and the effects of
> meteorological, hydrologic, and/or oceanographic conditions.
> Sea_level means mean sea level, which is close to the geoid in
> sea areas.
>
>
> ---
> 8.) duration_of_tidal_rise [ s ]
>
> Duration of rise is the interval from low water to high water. In
> combination with duration_of_tidal_fall they cover, on an average,
> a period of 12.42 hours for a semidiurnal tide or a period of 24.84
> hours for a diurnal tide. In a normal semidiurnal tide, duration of
> rise and duration of fall each will be approximately equal to 6.21
> hours, but in shallow waters and in rivers there is a tendency for
> a decrease in duration of rise and a corresponding increase in
> duration of fall. Due to the periodic tidal forces and the effects
> of meteorological, hydrologic, and/or oceanographic conditions.
>
>
> ---
> 9.) duration_of_tidal_fall [ s ]
>
> Duration of fall is the interval from high water to low water. In
> combination with duration_of_tidal_rise they cover, on an average,
> a period of 12.42 hours for a semidiurnal tide or a period of 24.84
> hours for a diurnal tide. In a normal semidiurnal tide, duration of
> rise and duration of fall each will be approximately equal to 6.21
> hours, but in shallow waters and in rivers there is a tendency for
> a decrease in duration of rise and a corresponding increase in
> duration of fall. Due to the periodic tidal forces and the effects
> of meteorological, hydrologic, and/or oceanographic conditions.
>
>
> ---
> 10.) duration_of_tide [ s ]
> (opt) tidal_period [ s ]
>
> Interval between two successive low waters. Sum of duration_of_tidal_rise
> and duration_of_tidal_fall. On an average, a period of 12.42 hours for
> a semidiurnal tide or a period of 24.84 hours for a diurnal tide. Due
> to the periodic tidal forces and the effects of meteorological,
> hydrologic, and/or oceanographic conditions.
>
>
> ---
> 11.) time_of_occurrence_of_tidal_high_water [ s ]
>
> Time when high water occurs. Due to the periodic tidal forces and
> the effects of meteorological, hydrologic, and/or oceanographic
> conditions.
>
>
> ---
> 12.) time_of_occurrence_of_tidal_low_water [ s ]
>
> Time when low water occurs. Due to the periodic tidal forces and
> the effects of meteorological, hydrologic, and/or oceanographic
> conditions.
>
>
> ---
> 13.) tidal_difference_for_time_of_occurrence_of_tidal_high_water [ s ]
>
> Difference in time of a high water at a subordinate station and at
> a reference station. The difference, when applied according to sign
> to the time at the reference station, gives the corresponding time
> for the subordinate station. Due to the periodic tidal forces and
> the effects of meteorological, hydrologic, and/or oceanographic
> conditions.
>
>
> ---
> 14.) tidal_difference_for_time_of_occurrence_of_tidal_low_water [ s ]
>
> Difference in time of a low water at a subordinate station and at
> a reference station. The difference, when applied according to sign
> to the time at the reference station, gives the corresponding time
> for the subordinate station. Due to the periodic tidal forces and
> the effects of meteorological, hydrologic, and/or oceanographic
> conditions.
>
>
> ---
> 15.) tidal_rise [ m ]
>
> Vertical difference between the water level at low water and the
> water level at the subsequent high water. Due to the periodic tidal
> forces and the effects of meteorological, hydrologic, and/or
> oceanographic conditions.
>
>
> ---
> 16.) tidal_fall [ m ]
>
> Vertical difference between the water level at high water and the
> water level at the subsequent low water. Due to the periodic tidal
> forces and the effects of meteorological, hydrologic, and/or
> oceanographic conditions.
>
>
> ---
> 17.) duration_of_wetting_due_to_tidal_flooding [ s ]
>
> Duration for which a location is covered with water due to tidal
> flooding. Within the intertidal zone, flooding may last from 0.00
> (always dry) up to, on an average, 12.42 hours (always wet) for a
> semidiurnal tide. Or up to, on an average, 24.84 hours for a diurnal
> tide. Due to the periodic tidal forces and the effects of
> meteorological, hydrologic, and/or oceanographic conditions.
>
>
> ---
> 18.) duration_of_drying_due_to_tidal_ebbing [ s ]
>
> Duration for which a location is not covered with water due to tidal
> ebbing. Within the intertidal zone, ebbing may last from 0.00
> (always wet) up to, on an average, 12.42 hours (always dry) for a
> semidiurnal tide. Or up to, on an average, 24.84 hours for a diurnal
> tide. Due to the periodic tidal forces and the effects of
> meteorological, hydrologic, and/or oceanographic conditions.
>
>
>
>
>
> G?nther Lang
>
>
>
> Bundesanstalt f?r Wasserbau - Dienststelle Hamburg
> Referat ?stuarsysteme II
> Wedeler Landstra?e 157
> 22559 Hamburg
> Telefon +49 (0) 40 81908 360
> E-Mail guenther.lang at baw.de <mailto:guenther.lang at baw.de>
>
>
>
> ---------------------------------------------
> This message (and any attachments) is for the recipient only. NERC is subject
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>
G?nther Lang
Bundesanstalt f?r Wasserbau - Dienststelle Hamburg
Referat ?stuarsysteme II
Wedeler Landstra?e 157
22559 Hamburg
Telefon +49 (0) 40 81908 360
E-Mail guenther.lang at baw.de
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