plotting a cut grib file with NCL

From: Andries De Vries <a.devries_at_nyahnyahspammersnyahnyah>
Date: Mon Dec 05 2011 - 11:08:25 MST

Dear people,

I have a problem with plotting cut grib files (ERA-Interim data) in NCL. Plotting, using the global file works perfectly. Now I want to make the same plot, but from a cut file for a specific region (lon:-60 to 100, lat: -10 to 90). The grib file is cut with use of the CDO program, using the command: 'cdo sellonlatbox'. However, when I plot the data, NCL gives the warning below. See also the text file with printed information of the original (global) and experiment (cut files) files and variables.

warning:GdsGAGrid: GRIB attributes La1 and/or La2 are incorrectly out of range of the gaussian latitude array (See GRIB Section 2 documentation)
warning:GdsGAGrid: Gaussian latitude coordinate array is partially or wholly undefined

The plot is flipped and stretched over the latitudes (see plot attached). Inverting the latitudes does not help, the plot is still stretched. Apparently NCL has difficulties dealing with latitude coordinates.To me it is not clear if the problem happens in NCL, or that the problem originates from cutting the files, leading to loss of coordinates or metadata. Using wgrib command, the cut grib file seems okay. I also did some experiments with cutting data for specific index instead of lat-lon coordinates as well as switching coordinates in the cdo command, but it all did not help, the plot stayed the same.

When I convert the cut file to netcdf format, no problems occur. NCL gives no warnings and the plot is perfectly fine. Does anyone have any idea about the problem of reading cut grib files in NCL? Suggestions would be most welcome. Thanks a lot!


ncl-talk mailing list
List instructions, subscriber options, unsubscribe:

Received on Mon Dec 5 11:08:38 2011

This archive was generated by hypermail 2.1.8 : Fri Dec 09 2011 - 13:09:09 MST