Content from 

https://confluence-test.ecmwf.int/display/ECC/Frequently+Asked+Questions

Summary

• Page:
  Order of setting fixed surface keys - ecCodes GRIB FAQ —

  This article relates to GRIB edition 2

  Problem

  Setting the fixed surface keys in the wrong order can lead to incorrect values.

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  MEMFS: How do I access the samples in ifs_samples - ecCodes GRIB FAQ —

  Problem

  If you try to load the samples file "gg_ml.tmpl", it can fail because that one is not in the usual samples location but in "ifs_samples". Normally you extend the ECCODES_SAMPLES_PATH to include the ifs_samples directory. But with MEMFS the samples (and also definitions) are not installed (instead they are all embeddedwithin the library.

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  grib_to_netcdf: skips Control Forecast when I convert Ensemble Forecast data - ecCodes GRIB FAQ —

  If you have a file with both Control and Perturbed forecasts, grib_to_netcdf will only convert the pf. Normally from 51 members in the GRIB file, only 50 appear in the netCDF.

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  grib_to_netcdf: Why do I get the error "Wrong number of fields... Try using the -T option" - ecCodes GRIB FAQ —

  You try to retrieve data from the ECMWF data archive in netCDF format but the retrieval fails with this message

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  Why I cannot set negative values for the longitude in GRIB 2 - ecCodes GRIB FAQ —

  GRIB 1 regulates that the longitude can be in either [-180, 180] or [0,360], GRIB 2 regulates that the longitude can only be in the interval [0,360]

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  Why can I read certain parameters using the grib tools, but not from my program - ecCodes GRIB FAQ —

  Your file may be encoded as a multi-field GRIB file. By default, grib tools have multi-field support enabled and the API disabled.

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  Why am I not able to set the missing value in the GRIB message - ecCodes GRIB FAQ —

  The GRIB format does keep track of missing values but through the use of a bitmap  It does not allow the specification of a missing value. Setting the missing value is a feature that can be used only when encoding the data values stored in a GRIB message.

• Page:
  Why does setting paramId/shortName fail sometimes - ecCodes GRIB FAQ —

  Problem

  You set the paramId or shortName on a given GRIB file but the command fails

  Solution

• Page:
  Why does grib_ls print "not_found" in some cases - ecCodes GRIB FAQ —

  This can happen in some cases when a mix of dissimilar GRIB messages are placed together in one file.

  Let's say you have a GRIB message M1 with 5 keys in its MARS namespace: stream, step, levtype, levelist and param. And another message M2 has 4 MARS keys: stream, step, levtype, param.

  grib_ls works by taking the keys in the namespace of the first message and uses those same keys for all subsequent messages. So it will display those keys in the first row of its output.

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  Why are there sometimes small negative precipitation accumulations - ecCodes GRIB FAQ —

  Periodically we receive reports of negative precipitation totals being computed from IFS output in GRIB.  Although such reports often refer to "negative precipitation accumulation", the same issue can affect any field accumulated from the start of the forecast and small but spurious positive accumulations are also possible.   Positive accumulations can lead to small increases in, say, solar radiation during night time hours when a zero increase is expected.  This page explains both why this occurs and the circumstances in which it occurs.

• Page:
  Python3: codes_write error: 'argument must be str, not bytes' - ecCodes FAQ —

  Problem

  When trying to write out a GRIB or BUFR message to a file using codes_write, an error is generated (an exception is thrown)

  Solution

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  grib_to_netcdf: why are some fields filled with missing values - ecCodes GRIB FAQ —

  Problem

  After using grib_to_netcdf to convert GRIB data to netCDF there are some fields in the output that are filled with missing values.

  For example, the following file contains seven GRIB messages:  temperature at six constant pressure levels: 1000 hPa, 850 hPa, 700 hPa, 500 hPa,400 hPa and 300 hPa and geopotential at 1000 hPa only.  An inventory of the contents of the files using the cdo info  command shows:

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  Getting an "relocation R_X86_64_32 against `.bss' cannot be used when making a shared object; recompile with -fPIC" - ecCodes FAQ —

  jasper library that has been linked statically is trying to be linked into a dynamic libgrib_api.so. Libraries linked to a dynamic library must use "relocatable" code, and normally static libraries aren't. Possible solutions

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  grib_to_netcdf: "Wrong number of fields... Try using the -T option" - Web API FAQ —

  Problem

  grib_to_netcdf: "Wrong number of fields... Try using the -T option"

  The request fail when it is trying to convert the GRIB file to netCDF.

• Page:
  Failure setting key changeDecimalPrecision - ecCodes GRIB FAQ —

  If you issue the command "grib_set -s changeDecimalPrecision=1 spectral.grib output", you can get an error