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Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Hi Eizi:Thanks for clarifying that terminology, I see that my understanding has been a bit fuzzy. I think I do indeed mean "Start of forecast", not the actual time the model was run.
Does your agency still use GRIB-1? If so, do you ever code anything other than the "Start of forecast" in the reference time ?
If you use GRIB-2, do you set "Significance of reference time" equal to 1 = "Start of forecast" ?
Finally, what in your opinion is the meaning of the other "Significance of reference time" codes, esp how does "Analysis" differ from "Start of forecast" ?
thanks, John On 11/26/2013 2:23 AM, Eizi TOYODA wrote:
Hi John, I'm not sure what do you mean by "run time". If you want the date/time at which the forecast model started, I don't think GRIB contains it. If you mean the initial time of forecast model, that is "Start of forecast" and it is really common to use this as reference time. Best, -- Eizi TOYODA: Japan Meteorological Agency Associate member of WMO/CBS/OPAG-ISS/IPET-DRMM Best Regards, -- Eiji (aka Eizi) TOYODA http://www.google.com/profiles/toyoda.eizi On Sat, Nov 23, 2013 at 3:03 AM, John Caron <caron@xxxxxxxxxxxxxxxx <mailto:caron@xxxxxxxxxxxxxxxx>> wrote: 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 _______________________________________________ thredds mailing list thredds@xxxxxxxxxxxxxxxx <mailto:thredds@xxxxxxxxxxxxxxxx> For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
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