Nan,
The problem is, udunits defines a month as having a specific length of
year/12 = 30.44 days, so if you use udunits to convert to anything else,
you won't end up where you think you will. The better practice is to use
days. It's not as "human readable", but it's the only way to do proper
conversions between time bases.
Grace and peace,
Jim
On 9/17/15 9:06 AM, Nan Galbraith wrote:
> While it's true that 'month is not a proper unit of measure',
> climatologies do in fact use months, not days, in calculating
> mean values. Adhering to udunits/CF in this regard could make
> the dates less easily understood.
>
> Regards - Nan
>
> On 9/11/15 1:34 PM, Karl Taylor wrote:
>> Dear Ajay,
>>
>> Since "month" is not a proper unit of measure, convert your times to
>> days and use a unit "days since ...".
>>
>> Also, it is normally a bad idea to have your base time set to a date
>> before the switch from Julian to Gregorian calendar. I suggest using
>> a base time of "1955-01-01" (i.e., the beginning of your
>> climatological period).
>>
>> I think the cell_methods should be:
>> cell_methods="area: mean depth: mean time: mean within years time:
>> mean over years";
>>
>> The time bounds should be (expressed in date/time format):
>>
>> climatology_bounds = "1955-01-01", "2012-04-01"
>>
>> and you can choose your time coordinate value as you think most
>> appropriate, e.g.,
>> the middle of the season of the first year of the climatology, or
>> the beginning of the first month of the first year of the
>> climatology, or
>> the middle of the season of the middle year of the climatology, or
>>
>> ???
>>
>>
>> Hope someone confirms this, as sometimes I make a mistakes.
>>
>> Karl
>>
>>
>>
>>
>> On 9/11/15 9:54 AM, Ajay Krishnan - NOAA Affiliate wrote:
>>> Dear CF members,
>>>
>>> I would like your input on the way climatological stats are being
>>> represented in a file that I am working on. I believe that I am not
>>> using the time and the climatological_bounds properly:
>>>
>>> Seasonal SST
>>>
>>> Average seasonal temperature (Jan-Mar) for 6 decades (1955-2012)
>>>
>>> dimensions:
>>> time=1;
>>> nv=2;
>>> variables:
>>>
>>>
>>> double time(time);
>>> time:climatology="climatology_bounds";
>>> time:units="months since 0000-01-01";
>>> double climatology_bounds(time,nv);
>>>
>>>
>>> double climatology_bounds(time,nv);
>>>
>>> climatology_bounds:comment=? This variable defines the bounds of the
>>> climatological time period for each time? ;
>>>
>>> float t_mn(time,lat,lon,depth);
>>> t_mn:standard_name: ?sea_water_temperature? ;
>>>
>>> t_mn:long_name: ?Average of all unflagged interpolated values at
>>> each standard depth level for sea_water_temperature in each
>>> grid-square which contain at least one measurement.? ;
>>>
>>> t_mn:cell_methods: ?area: mean depth: mean time: mean? ;
>>>
>>>
>>> data: // time coordinates translated to date/time format
>>> time= ?1.5? ;
>>>
>>> climatology_bounds=?0.0?, ?3.0? ;
>>>
>>>
>>> The CF examples are helpful but my case is different where in I have
>>> just 1-time co-ordinate in my file. In the above case, what is the
>>> best way to record time and climatology bounds?
>>>
>>>
>>> Thanks,
>>>
>>> Ajay
>>>
>>>
>
--
CICS-NC <http://www.cicsnc.org/> Visit us on
Facebook <http://www.facebook.com/cicsnc> *Jim Biard*
*Research Scholar*
Cooperative Institute for Climate and Satellites NC <http://cicsnc.org/>
North Carolina State University <http://ncsu.edu/>
NOAA National Centers for Environmental Information <http://ncdc.noaa.gov/>
/formerly NOAA?s National Climatic Data Center/
151 Patton Ave, Asheville, NC 28801
e: jbiard at cicsnc.org <mailto:jbiard at cicsnc.org>
o: +1 828 271 4900
/Connect with us on Facebook for climate
<https://www.facebook.com/NOAANCEIclimate> and ocean and geophysics
<https://www.facebook.com/NOAANCEIoceangeo> information, and follow us
on Twitter at _at_NOAANCEIclimate <https://twitter.com/NOAANCEIclimate> and
_at_NOAANCEIocngeo <https://twitter.com/NOAANCEIocngeo>. /
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20150917/7dcb1c8c/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: CicsLogoTiny.png
Type: image/png
Size: 15784 bytes
Desc: not available
URL: <http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20150917/7dcb1c8c/attachment-0001.png>
Received on Thu Sep 17 2015 - 07:32:51 BST
