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Overview

Import type grib2 supports :

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• importing ensembles,
• importing grid data from separate layers (z-dimension)
• importing grid data that are distributed over the several files, e.g. all forecasts in one file, one file per forecast, et cetera.

For the users of 2016.02 or higher  

Since Fews version 2016.02  the new NetCdf version 4.6 is used to read grib2 files. There are two important points the users should be aware of :

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• Download the current version of Panoply from http://www.giss.nasa.gov/tools/panoply/
• Open grib2 file in Panoply
• In the column Name you can find the parameters available in the grib2 file

• These parameter names should be configured in IdMap.xml

Property "Use_Grib2_Parameter_Name" to read parameter names from attribute Grib2_Parameter_Name

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Fews 2016.02  assigns  4,5,6 to the ensemble members, so the same numbers as coded in the grib2.

Grib2 and  HyFs GFS accumulated series

In Hyfs GFS grib2 files there are 2  types of accumulated precipitation series :   series accumulated from the start of the forecast and series accumulated  from the nearest 6 hr interval 

However, NetCdf library , used to decode the grib2 format,  does not provide  a separate variable for each  series.  Netcdf library combines both accumulated series in one series (mixed intervals  series)
In picture below there are two values for  event time  2021-10-11 12:00  :   the first one  is accumulated value from the start of the forecast ,  the second one  is  accumulated value for the  last 6 hours

Using property   “Read_Grib2_Accumulation_Message_Number”  we can specify which one is required: 
<int key="Read_Grib2_Accumulation_Message_Number" value="1"/>    or
<int key="Read_Grib2_Accumulation_Message_Number" value="2"/>

This property applies  to all accumulated series in the Hyfs GFS grib2 file.  

Note:  presently it is assumed that there is  one single  grib2 file for every  single observation time.