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ERA5: no num_metgrid_levels in met_em files

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I'm downloading ERA5 data following, i.e. 38 vertical levels. Note it does not say I need to pre-process the grib files, as is the case of using the 138 model levels.

I'm using WPS-4.1, and ungrib works fine, and metgrid runs and does not complain (says "Successful completion of metgrid" at the end).

When I try to run obsgrid-3.8, I get a segfault. Using ncdump -h to look at a met_em*.nc file, I see the dimension num_metgrid_levels is missing.

netcdf met_em.d04.2013-12-19_12\:00\:00 {
        Time = UNLIMITED ; // (1 currently)
        DateStrLen = 19 ;
        west_east = 78 ;
        south_north = 75 ;
        num_st_layers = 4 ;
        num_sm_layers = 4 ;
        south_north_stag = 76 ;
        west_east_stag = 79 ;
        z-dimension0003 = 3 ;
        z-dimension0132 = 132 ;
        z-dimension0012 = 12 ;
        z-dimension0016 = 16 ;
        z-dimension0024 = 24 ;
        char Times(Time, DateStrLen) ;
        float PRES(Time, south_north, west_east) ;

I must be missing a step, not given in the dreambooker page. Suggestions?

Would there be a use-case where metgrid writing only the surface-level data would be useful?

If not, perhaps metgrid should issue a warning that no upper-level data were found. Might be worth a few lines of code..

Thank you for the suggestion! Would you mind opening an "issue" about this on our WPS GitHub repository page?