What is the meaning of a GRIB field with a header section (PDS), but no data values?
[7/10/96] According to GRIB convention, when the entire field contains a constant value, the field width (octet 11) is set to zero and no data values are packed. The value for all points in the field is the reference value. • What should be used as the valid time for fields in the grb2d file? [6/19/96] Fields in the grb2d file are either 6 hour averages or 6 hour forecasts. The GRIB reference time is used in the file name, BUT the valid time is actually 6 hours later for the forecast fields. The average fields are averages of the 6 hour period from the reference time to 6 hours later. The GRIB PDS information correctly specifies the time and the GrADS package will assign the proper time. • PRESmsl vs. PRMSLmsl: [6/19/96] These two variables are derived using slightly different algorithms for the same sea-level-pressure. Check this pres.msl for exact definitions. • Negative PWAT values: [6/19/96] This is a common phenomenon in numerical models. The negative values are to be flagged for
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- What is the meaning of a GRIB field with a header section (PDS), but no data values?
