Re: [CF-metadata] convention for climatological time units
Dear John But by main issue is that in Example 7.8 the time data entered in the file is still described as having units days since 1960-1-1 which really isn't so. It is equally logically days since 1991-1-1. In reality it's just days since Jan 1 of any year. Yes. This convention doesn't prevent the practice of assigning time values thus: double time(time); time:units=days since 1960-1-1; data: time = 154575 ... double time(time); time:units=days since 1959-1-1; data: time = 380 410 440 ... udunits would consider these times to be identical, but for a monthly climatology starting the counting at 380 is just nuts. What you say is correct; these are equivalent. I think the issue is that you don't need to impute any meaning to the reference time that is used in the units string. It is arbitrary. It could be anything. The only point of it is to encode components of time (year, month, day, etc...) into numbers. The climatological interpretation of these date-times is based on what they mean when decoded into components. Once they are in components, the units string - both the unit and the reference time - are irrelevant. They are not needed any more, because they do not contain any extra metadata. CF climatological time bounds encode, in a compact way, both the range of years used to compute the climatology, and the time within the climatological year. You're right, they do not indicate the weighting used to compute a time-mean or other statistic. This is generally the case for all kinds of axis, not just climatological time. cell_methods provide a way to record, in a non-standardised way (in brackets) a comment about the weights. So far no-one has raised a need for a standardised way to do this. Best wishes Jonathan ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
[CF-metadata] sea_water_pressure
Dear All, It has been pointed out to me that the SeaDataNet NetCDF specification uses 'sea_water_pressure' as the Standard Name in cases where pressure is used as the z co-ordinate in observational data such as CTD profiles. The definition for this Standard Name is: the pressure that exists in the medium of sea water. It includes the pressure due to overlying sea water, sea ice, air and any other medium that may be present. Consequently the expected pressure z co-ordinate labelled 'sea_water_pressure' would be approximately 10 decibars at the sea surface. However, it is almost universal practice to either calibrate or correct the pressure z co-ordinate so that it reads zero at the sea surface. Consequently, I think we need a new Standard Name: sea_water_pressure_due_to_sea_water defined as the pressure that exists in the medium of sea water due to overlying sea water. Excludes the pressure due to sea ice, air and any other medium that may be present. Apologies to anybody else who like me had used 'sea_water_pressure' for their Z co-ordinate without looking at the definition. 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! This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system. ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] [CF Metadata] #68: CF data model and reference implementation in Python
On Thu, Jan 10, 2013 at 10:26 AM, Chris Barker - NOAA Federal chris.bar...@noaa.gov wrote: but is that the data model? or is that a particular encoding for a particular file format? I think the later. Another example of encoding vs. data model: An array of integers is a data model The binary representation of that array is encoding: is it big or little endian, for instance. Netcdf already abstracts that out for you -- your code does not need to care. I think this principle could be extended to higher-lever abstractions like datetimes, and encodings like integer*scale+offset -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/ORR(206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] sea_water_pressure
Hi Roy, This looks sensible to me. Philip --- Dr Philip Cameron-Smith, p...@llnl.gov, Lawrence Livermore National Lab. --- From: CF-metadata [mailto:cf-metadata-boun...@cgd.ucar.edu] On Behalf Of Lowry, Roy K. Sent: Thursday, January 10, 2013 1:01 AM To: cf-metadata@cgd.ucar.edu Cc: sdn2-net...@seadatanet.org Subject: [CF-metadata] sea_water_pressure Dear All, It has been pointed out to me that the SeaDataNet NetCDF specification uses 'sea_water_pressure' as the Standard Name in cases where pressure is used as the z co-ordinate in observational data such as CTD profiles. The definition for this Standard Name is: the pressure that exists in the medium of sea water. It includes the pressure due to overlying sea water, sea ice, air and any other medium that may be present. Consequently the expected pressure z co-ordinate labelled 'sea_water_pressure' would be approximately 10 decibars at the sea surface. However, it is almost universal practice to either calibrate or correct the pressure z co-ordinate so that it reads zero at the sea surface. Consequently, I think we need a new Standard Name: sea_water_pressure_due_to_sea_water defined as the pressure that exists in the medium of sea water due to overlying sea water. Excludes the pressure due to sea ice, air and any other medium that may be present. Apologies to anybody else who like me had used 'sea_water_pressure' for their Z co-ordinate without looking at the definition. 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! This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system. ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] sea_water_pressure
It looks sensible to me, too, but I have to ask a stupid question. Of all the
data with sea_water_pressure CF standard names in the world, how many are
actually presenting what CF defines that to be? (If the answer is very few,
maybe the answer is that the definition is just mis-stated for what the
community expected, and we need a new term to go with the existing definition.)
(Yes, this is a perspective that only an ontologist could offer without
embarrassment.)
John
On Jan 10, 2013, at 15:16, Cameron-smith, Philip wrote:
Hi Roy,
This looks sensible to me.
Philip
---
Dr Philip Cameron-Smith, p...@llnl.gov, Lawrence Livermore National Lab.
---
From: CF-metadata [mailto:cf-metadata-boun...@cgd.ucar.edu] On Behalf Of
Lowry, Roy K.
Sent: Thursday, January 10, 2013 1:01 AM
To: cf-metadata@cgd.ucar.edu
Cc: sdn2-net...@seadatanet.org
Subject: [CF-metadata] sea_water_pressure
Dear All,
It has been pointed out to me that the SeaDataNet NetCDF specification uses
'sea_water_pressure' as the Standard Name in cases where pressure is used as
the z co-ordinate in observational data such as CTD profiles. The definition
for this Standard Name is:
the pressure that exists in the medium of sea water. It includes the
pressure due to overlying sea water, sea ice, air and any other medium that
may be present.
Consequently the expected pressure z co-ordinate labelled
'sea_water_pressure' would be approximately 10 decibars at the sea surface.
However, it is almost universal practice to either calibrate or correct the
pressure z co-ordinate so that it reads zero at the sea surface.
Consequently, I think we need a new Standard Name:
sea_water_pressure_due_to_sea_water defined as
the pressure that exists in the medium of sea water due to overlying sea
water. Excludes the pressure due to sea ice, air and any other medium that
may be present.
Apologies to anybody else who like me had used 'sea_water_pressure' for their
Z co-ordinate without looking at the definition.
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!
This message (and any attachments) is for the recipient only. NERC is subject
to the Freedom of Information Act 2000 and the contents of this email and any
reply you make may be disclosed by NERC unless it is exempt from release
under the Act. Any material supplied to NERC may be stored in an electronic
records management system.
___
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
John Graybealmailto:jgrayb...@ucsd.edu phone: 858-534-2162
Product Manager
Ocean Observatories Initiative Cyberinfrastructure Project:
http://ci.oceanobservatories.org
Marine Metadata Interoperability Project: http://marinemetadata.org
___
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] sea_water_pressure
Hi John, I have seen similar situations in atmospheric chemistry. I participated in an intercomparison in which we submitted exactly what the std_name required, only to find out that every other group had submitted what they assumed it meant, which was several orders of magnitude different. I think the bar for retroactively changing a definition should be very high (without commenting on the merits of your case). One thing we can do to help, without causing any problems, is to add to existing descriptions a list of related std_names so that a user will get a 'heads up' to look at other std_names. I know this is only a partial solution, but better than nothing. Best wishes, Philip --- Dr Philip Cameron-Smith, p...@llnl.gov, Lawrence Livermore National Lab. --- From: John Graybeal [mailto:jgrayb...@ucsd.edu] Sent: Thursday, January 10, 2013 3:48 PM To: Cameron-smith, Philip Cc: Lowry, Roy K.; cf-metadata@cgd.ucar.edu; sdn2-net...@seadatanet.org Subject: Re: [CF-metadata] sea_water_pressure It looks sensible to me, too, but I have to ask a stupid question. Of all the data with sea_water_pressure CF standard names in the world, how many are actually presenting what CF defines that to be? (If the answer is very few, maybe the answer is that the definition is just mis-stated for what the community expected, and we need a new term to go with the existing definition.) (Yes, this is a perspective that only an ontologist could offer without embarrassment.) John On Jan 10, 2013, at 15:16, Cameron-smith, Philip wrote: Hi Roy, This looks sensible to me. Philip --- Dr Philip Cameron-Smith, p...@llnl.govmailto:p...@llnl.gov, Lawrence Livermore National Lab. --- From: CF-metadata [mailto:cf-metadata-boun...@cgd.ucar.edu] On Behalf Of Lowry, Roy K. Sent: Thursday, January 10, 2013 1:01 AM To: cf-metadata@cgd.ucar.edumailto:cf-metadata@cgd.ucar.edu Cc: sdn2-net...@seadatanet.orgmailto:sdn2-net...@seadatanet.org Subject: [CF-metadata] sea_water_pressure Dear All, It has been pointed out to me that the SeaDataNet NetCDF specification uses 'sea_water_pressure' as the Standard Name in cases where pressure is used as the z co-ordinate in observational data such as CTD profiles. The definition for this Standard Name is: the pressure that exists in the medium of sea water. It includes the pressure due to overlying sea water, sea ice, air and any other medium that may be present. Consequently the expected pressure z co-ordinate labelled 'sea_water_pressure' would be approximately 10 decibars at the sea surface. However, it is almost universal practice to either calibrate or correct the pressure z co-ordinate so that it reads zero at the sea surface. Consequently, I think we need a new Standard Name: sea_water_pressure_due_to_sea_water defined as the pressure that exists in the medium of sea water due to overlying sea water. Excludes the pressure due to sea ice, air and any other medium that may be present. Apologies to anybody else who like me had used 'sea_water_pressure' for their Z co-ordinate without looking at the definition. 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! This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system. ___ CF-metadata mailing list CF-metadata@cgd.ucar.edumailto:CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata John Graybealmailto:jgrayb...@ucsd.edu phone: 858-534-2162 Product Manager Ocean Observatories Initiative Cyberinfrastructure Project: http://ci.oceanobservatories.org Marine Metadata Interoperability Project: http://marinemetadata.org ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
