[gradsusr] 365 day calendar question

[Andrew Friedman]

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
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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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Andrew Friedman
andfried at berkeley.edu