[gradsusr] gribmap problem with sub-hour time intervals

Thu Apr 8 13:37:16 EDT 2010

Hi, Steve--
You are correct, GrADS is rounding %f2 to the nearest hour, and I do  
not immediately see the benefit of doing this. I will talk it over  
with Brian. In any case, a template of %f2%n2 is not quite right since  
you are mixing forecast times (%f2) with valid times (%n2). If your  
initial time was not 00:00z, then your template substitution would  
fail on the first filename. And there is no template substitution for  
forecast minutes, so there's no general solution for what you're  
trying to do. I suggest using the %t or %tm templates, and renaming  
your output files according to time index instead of forecast time.
--Jennifer
p.s. If your initial time is always going to be 00:00z, and your  
forecast doesn't go beyond 23 hours and 40 minutes, then %h2%n2 will  
work in your current descriptor, but that is a bit of a hack.

will not work if your start time is , I will talk it over with Brian.  
In the meanwhile,

On Apr 7, 2010, at 3:15 PM, Masters.Steve wrote:

> I have a set of grib files produced by WRF using wrfpost that are at  
> sub-hour intervals.  On my outer grid, I am writing out data at 20  
> minute intervals.  The top of the GrADS control file looks like...
>
> dset ^0901020000_sfcout_arw_d01.grb1f%f2%n200
> index ^d01sfc.idx
> *  produced by grib2ctl v0.9.12.5p45
> dtype grib 255
> options template
> tdef 19 linear 00Z02jan2009 20mn
>
> I'm using the template option so I can use GrADS to access multiple  
> files in a single session without concatenating them together.  The  
> output from gribmap is listed below...
>
> gribmap -i d01sfc.ctl
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f000000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f002000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f014000   
> <======
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f010000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f012000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f024000   
> <======
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f020000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f022000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f034000   
> <======
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f030000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f032000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f044000   
> <=====
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f040000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f042000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f054000   
> <=====
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f050000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f052000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f064000   
> <=====
> grib1map warning: could not open GRIB file:  
> 0901020000_sfcout_arw_d01.grb1f064000
> grib1map:  opening GRIB file: 0901020000_sfcout_arw_d01.grb1f060000
> grib1map:  reached end of files
> grib1map:  writing the map...
>
> At the "40-minute" point, the hour is incorrectly flipped to the  
> next value.  When I did this same operation against 5-minute output,  
> the error happens as soon as I reach the 30-minute point of the  
> hour.  It seems like some kind of rounding is happening within  
> gribmap when it attempts to resolve the hour part of the time.   
> Looking at the output from GrADS, it appears to me that the grib  
> index that is created is invalid as I get "bumps" in the time series  
> that indicate data are being plotted at the wrong time (or not at  
> all) in the second half of each hour.
>
> This problem is seen with gribmap 1.9b4, 2.0.a5 and also with the  
> very latest version 2.0a8.
>
> Stephen Masters   masters.steve at ensco.com
> ENSCO, Inc.
> Melbourne, FL
>
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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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