[gradsusr] 365 day calendar question

[Jennifer Adams]

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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