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.
Thanks!
John
