[CF-metadata] Is there ambiguity in labelling climatological time. Was: CF-metadata Digest, Vol 144, Issue 25

From: David Charles Hassell <d.c.hassell>
Date: Thu, 30 Apr 2015 08:13:42 +0000

Hello Chris, Charlie, Karl, ....

Personally, I prefer to use the first (or last) year, as this is unambiguous. Ambiguities about how to define the mid-year could arise depending on whether number of years in the climatology is odd or even. The mid-year could, of course, be carefully defined, but the definition would be arbitrary, I think.

(I used "year" here, but the same argument applies to "day")

All the best,

David
________________________________________
From: CF-metadata [cf-metadata-bounces at cgd.ucar.edu] on behalf of Little, Chris [chris.little at metoffice.gov.uk]
Sent: 30 April 2015 08:58
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Is there ambiguity in labelling climatological time. Was: CF-metadata Digest, Vol 144, Issue 25

Dear Charlie, Karl, and other CF'ers,

If you can all agree on a preferred convention for whether the first, last, mid, or some other date is used to label a climatology, or a way of unambiguously labelling which has been used, it would make lots of people happier.

Does anyone know of any WMO Climate Commission, or Commission for Basic Systems, guidance?

Best wishes, Chris

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Today's Topics:

   1. Is there ambiguity in labeling climatological time
      coordinates? (Charlie Zender)
   2. Re: Is there ambiguity in labeling climatological time
      coordinates? (Karl Taylor)
   3. Ancillary variables in coordinate variables (latitude,
      longitude, ...) (Kristian Sebasti?n)


----------------------------------------------------------------------

Message: 1
Date: Wed, 29 Apr 2015 17:11:07 -0700
From: Charlie Zender <zender at uci.edu>
To: CF Metadata Mail List <cf-metadata at cgd.ucar.edu>
Subject: [CF-metadata] Is there ambiguity in labeling climatological
        time coordinates?
Message-ID: <5541731B.50800 at uci.edu>
Content-Type: text/plain; charset=utf-8; format=flowed

Dear CF'ers,

The draft 1.7 conventions example Example 7.8. Climatological seasons has the following for the time coordinate:

time="1960-4-16", "1960-7-16", "1960-10-16", "1961-1-16" ;

All else being equal, are the values

time="1975-4-16", "1975-7-16", "1975-10-16", "1976-1-16" ;

also be acceptable for this same example?

The underlying question is whether there is permissible ambiguity in the time coordinate values, or if for some reason the beginning year (1960) must be used as in this example. An alternative choice that seems reasonable to me is the use of the midpoint year (1975). I'm unsure whether 1960 was chosen arbitrarily or because one is expected to apply the minimum operation discussed in this example (seasonal minimum temperature) to the values of the time coordinate as well.

Thanks,
Charlie

--
Charlie Zender, Earth System Sci. & Computer Sci.
University of California, Irvine 949-891-2429 )'(
------------------------------
Message: 2
Date: Wed, 29 Apr 2015 18:22:45 -0700
From: Karl Taylor <taylor13 at llnl.gov>
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Is there ambiguity in labeling
        climatological time coordinates?
Message-ID: <554183E5.1080104 at llnl.gov>
Content-Type: text/plain; charset="windows-1252"; Format="flowed"
Hi Charlie,
I think the only guidance CF provides is:
"The time coordinates should be values that are representative of the
climatological time intervals, such that an application which does not
recognise climatological time will nonetheless be able to make a
reasonable interpretation"
I think for your case any consecutive dates within the climatological
period would do, but like you I'd probably choose the middle year (or
perhaps the first year, as in the example).
Hope others will correct me if I'm wrong.
Karl
On 4/29/15 5:11 PM, Charlie Zender wrote:
> Dear CF'ers,
>
> The draft 1.7 conventions example Example 7.8. Climatological seasons
> has the following for the time coordinate:
>
> time="1960-4-16", "1960-7-16", "1960-10-16", "1961-1-16" ;
>
> All else being equal, are the values
>
> time="1975-4-16", "1975-7-16", "1975-10-16", "1976-1-16" ;
>
> also be acceptable for this same example?
>
> The underlying question is whether there is permissible ambiguity
> in the time coordinate values, or if for some reason the
> beginning year (1960) must be used as in this example. An alternative
> choice that seems reasonable to me is the use of the midpoint year
> (1975). I'm unsure whether 1960 was chosen arbitrarily or because one
> is expected to apply the minimum operation discussed in this example
> (seasonal minimum temperature) to the values of the time coordinate
> as well.
>
> Thanks,
> Charlie
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Message: 3
Date: Thu, 30 Apr 2015 08:43:54 +0200
From: Kristian Sebasti?n <ksebastian at socib.es>
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Ancillary variables in coordinate variables
        (latitude, longitude, ...)
Message-ID:
        <CAGfa=MDW7dpnpZj=EOJgGrK2eQ9o1Nvtz_dcUx-EeMH4MyBWXw at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Dear CF community,
We have some dataset with quality controls applied to the coordinate
variables, such as latitude and longitude coordinate. The result are
quality control variables that we associate as ancillary variables of the
coordinate variables with the ancillary_variables attribute. For example,
the LAT coordinate variable has the ancillary variable QC_LAT. The dataset
http://thredds.socib.es/thredds/dodsC/drifter/surface_drifter/drifter_svp052-ime_svp017/L1/2014/dep0001_drifter-svp052_ime-svp017_L1_2014-05-25.nc
The cf-conventions clarifies the use of the ancillary_variables attribute
for data variables but not for coordinate variables. My question is, Is the
ancillary_variables attribute in coordinates variables compliant with the
cf-conventions?
Best regards,
Kristian
--
Kristian Sebastian Blalid
SOS Division: Data Center Technical
Tel: 971439860 - Fax: 971439979
E-mail: kristian.sebastian at socib.es
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Received on Thu Apr 30 2015 - 02:13:42 BST