Re: Problems on reading GRIB2 files

Dear Dave,

Thanks for your reply. I have just checked the raw data and found that Section 4, Octets 23-28 provide information showing the records are in different pressure levels. Product definition template number 15 indicates the type of data (Octet 23 "Type of first fixed surface", 24 "Scale factor of first fixed surface" and 25-28 "Scaled value of first fixed surface" ). Is there a need to update the code table of NCL in order to get the data decoded properly?

Thanks,

Johnny.

Hi Johnny,
You are correct that NCL is ignoring some records. That is because they have the appearance of being duplicate records. There are 12 records in the file. The first six are spatial averages of "Icing" on a global grid and the second six are spatial maximum values on a global grid. The all have the same initial time and forecast time, and have no specified level type or value. Also the product definition template number (15) does not indicate that they are are intended to be individual members of an ensemble run. Using NCL's scheme for arranging similar GRIB records into arrays, NCL finds no way to differentiate them (although their data values may well be different) and therefore ignores all but 2 of the records. A record-oriented tool such as wgrib2 just prints the contents of each record individually and does not try to relate them to each other. 
Do you know how the records are supposed to be differentiated? Perhaps there is a characteristic that NCL should be noticing but is not. Can you send back the output of whatever tool you are using that might give a clue? Thanks, -dave 
On Oct 21, 2010, at 1:53 AM, Tam Johnny wrote:
Found that there are missing some variables/fields after reading a GRIB2 file by NCL (Version 5.2.1). There is more information available when I decode with other software. Is there any way to solve the problem. Attached please find the file for checking. Thanks.

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Received on Fri Oct 22 04:03:43 2010