[netcdf-java] Help with GRIB encoding - what is "reference time of data" ??

The question is whether the CDM can assume that GRIB "Reference time of data" is the "run time" of a forecast model.

In GRIB-1 docs, in the PDS there is:

"Reference time of data – date and time of start of averaging or accumulation period"

In GRIB-2 in Identification section, there is:

12 Significance of reference time (see Code table 1.2)

Reference time of data:

13–14 Year (4 digits)
15 Month
16 Day
17 Hour
18 Minute
19 Second

And Code table 1.2 has the following:

Code Table Code table 1.2 - Significance of reference time (1.2)
    0: Analysis
    1: Start of forecast
    2: Verifying time of forecast
    3: Observation time
   -1: Reserved
   -1: Reserved for local use
  255: Missing

None of this obviously refers to "run time", although I suspect that's how many centers use it. However, it appears that when you want to define a time interval, say "average of the temperature, starting 12 hours and ending 24 hours from reference, you may use the reference time to define the start of that interval. In which case, its not the runtime. Im hoping thats not the case, that reference time is the same as the run time for forecast models.

So if you know how to interpret these for any or all datasets, please send me a note, or post to this group. Please pass this question on to anyone who might be willing to contribute.



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