(RESOLVED) Why GRIB file must be linked and have specific extenssion

Topics related to running the ungrib.exe program
Post Reply
todor_Gai
Posts: 19
Joined: Wed Jun 17, 2020 12:48 pm

(RESOLVED) Why GRIB file must be linked and have specific extenssion

Post by todor_Gai » Thu Jun 25, 2020 7:53 am

Hi,
as a new user I was wondering why the provided to ungrib data must be linked and why isn't there property in namelist.wps that points to
directory with the input files ?
Also why the number of input files is limited by the number of different extensions (AAA, AAB, ...) ?
What happens if I need to use more input files ?

Thank you

kwerner
Posts: 1926
Joined: Wed Feb 14, 2018 9:21 pm

Re: Why GRIB file must be linked and have specific extenssion

Post by kwerner » Fri Jun 26, 2020 7:59 pm

Hi,
This is just the way the code was written many years ago. I personally am not a software engineer, but I'm certain there was a good reason for this method to enable the ungrib executable to work in the cleanest way possible. It is possible to modify the code to allow additional files if one should use more than the total possible combinations of 3 alphabetic values. Do you need to do that, or are you just asking, in general?
NCAR/MMM

todor_Gai
Posts: 19
Joined: Wed Jun 17, 2020 12:48 pm

Re: Why GRIB file must be linked and have specific extenssion

Post by todor_Gai » Tue Jun 30, 2020 3:43 pm

Hi,
Thank you for the response. I might need to use more grib files than the currently possible.
Can this be done only by modifying the link_grib.csh or changes are needed in the ungrib source ?

mgduda
Posts: 374
Joined: Mon Feb 26, 2018 7:35 pm

Re: Why GRIB file must be linked and have specific extenssion

Post by mgduda » Tue Jun 30, 2020 4:14 pm

If you need to process more than 26^3 GRIB files, the easiest approach would be to just process the files in batches. These batches of files could even be processed in parallel, e.g., on different nodes of a computing cluster, since the processing of one GRIB file is (almost) independent of the processing of other GRIB files; the only cases in which processing of a time period is dependent on other time periods is when the ungrib program needs to perform temporal interpolation for any GRIB fields missing at the time in question.
NCAR/MMM

todor_Gai
Posts: 19
Joined: Wed Jun 17, 2020 12:48 pm

Re: Why GRIB file must be linked and have specific extenssion

Post by todor_Gai » Wed Jul 01, 2020 9:58 am

Hi,
Thank you for the useful reply. I will try it when needed.

Post Reply

Return to “ungrib”