Re: [netcdf-java] Problem with CFS GRIB2 files

Dear Igor and John,

This is the interpretation that I'm doing about the monthly average datasets from the CFS:

after reading the Operational CFS doc:

in my opinion is that the average is for the 201103 month, and precisely for the interval:
[2011-03-09, 2011-03-31]


Antonio S. Cofiño
Grupo de Meteorología de Santander
Dep. de Matemática Aplicada y
        Ciencias de la Computación
Universidad de Cantabria
Escuela de Caminos
Avenida de los Castros, 44
39005 Santander, Spain
Tel: (+34) 942 20 1731
Fax: (+34) 942 20 1703

El 13/03/2011 15:40, John Caron escribió:
Hi Igor:

So the practical question is whether the data in the file represents a monthly average in the interval [2011-02-09, 2011-03-09] or [2011-03-09, 2011-04-09] .

My interpretation is the former; i interpret this in the Id section:

 RefTimeSignif = Start of forecast
 RefTime       = 2011-03-09T00:00:00Z

as saying that was the point in the forecast run when this data was written out. A forecast run could only average times it has already computed, so it couldnt be into the future. One could argue that RefTimeSignif is wrong or misleading.

i assume its probably important to your science to get this right. it would be great if you could track this down from the originators and report what the actual meaning is.

Its unfortunate that for all the work put into GRIB, these ambiguities still exist. Ive recently been arguing that a reference implementation of GRIB is needed so that there is an authoritative answer for both readers and writers of GRIB. If anyone is interested, please have a look at

On 3/12/2011 10:15 PM, Oleynikov Igor Sergeevich wrote:
Hi John!

I think that date in section 1 more important then date in PDS section. In my mind date of start of forecast is 2011-03-09. The end date of averaging is 2011-04-09. And of course it is an error into this dataset. I have just
started working with these data. I will write a solution to this problem
when I do it.

Best regards,


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