[gradsusr] 365 day calendar question

[Jennifer Adams]

Yes. Use 01jan1870. --Jennifer

On May 29, 2012, at 9:09 PM, Andrew Friedman wrote:

> Thank you very much, Jennifer.
> 
> One small follow-up: For monthly means using the date format without hours, is the beginning of the month preferred in e.g. '01Jan1870' over '15Jan1870'?
> 
> Andrew
> 
> On May 29, 2012, at 3:23 PM, Jennifer Adams wrote:
> 
>> Hi, Andrew -- 
>> 
>> On May 29, 2012, at 4:46 PM, Andrew Friedman wrote:
>> 
>>> Hi GrADS users,
>>> 
>>> I have a small question about best practices for writing a control file for 365 day calendar output.
>>> 
>>> I've been succesfully able to open CMIP3 model monthly netcdf files with a 365 calendar using xdfopen,
>>> following previous instructions on the GrADS forum:
>>> http://gradsusr.org/pipermail/gradsusr/2011-June/013406.html
>>> 
>>> with a line like 'TDEF time 1560 LINEAR 16Jan1870 1mo' in the control file
>> Many netcdf files express a monthly time axis value for January 1870 as "15.5 days since 01-01-1870." This is to place the grid point squarely in the middle of the month, to give you the idea that the value represents a monthly mean. GrADS is not so fussy about this; a date stamp of 01jan1870 is good enough to represent a january monthly mean, in fact, it is preferred over something like 12Z15jan1870. 
>> 
>>> 
>>> Is it important that I also include the line
>>> ' OPTIONS 365_day_calendar' 
>>> in the control file when I am opening monthly data?
>> No, because 365-day calendars do not affect time handling for monthly time axes.
>> 
>>> Or is this only important for daily data?
>> The 365_day_calendar option is essential for daily or hourly time axes. 
>> 
>>> It doesn't seem to cause any changes, but I'm writing control files for many files and am wondering if there could be some differences in the time axis. 
>>> 
>>> Thanks much,
>>> Andrew
>>> 
>>> 
>>> Andrew Friedman
>>> Graduate Student, UC Berkeley Geography
>>> andfried at berkeley.edu
>>> _______________________________________________
>>> gradsusr mailing list
>>> gradsusr at gradsusr.org
>>> http://gradsusr.org/mailman/listinfo/gradsusr
>> 
>> --
>> Jennifer M. Adams
>> IGES/COLA
>> 4041 Powder Mill Road, Suite 302
>> Calverton, MD 20705
>> jma at cola.iges.org
>> 
>> 
>> 
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>> gradsusr at gradsusr.org
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> 
> Andrew Friedman
> andfried at berkeley.edu
> 
> 
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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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