Introduction

Whenever -set_metadata option is "executed", one line of the data file is read, the metadata is then applied to the current (sub-)message. For example, your grib file has 3 messages and you want to alter the metadata. Here is a metadata file that could be used to alter the grib file.

0:0:d=2009010100:HGT:500 mb:anl:scale=0,0:
0:0:d=2009010100:TMP:2 m above ground:anl
0:0:d=2009010106:HGT:500 mb:12 hour forecast:scale=0,0

The format of the metadata file resembles the wgrib2 inventory by design. The first and second fields are ignored by by -set_metadata. In practice, the first first is the record number and the second field is the byte location of the template to be used. (A template file could be a collection of templates.) The third through sixth fields are the date code, variable name, level and ftime. Finally the remaining fields are optional and order independent.

		Optional fields

    scale=I,J			set decimal scaling (I) and binary scaling (J)
    center=I                    set center to I
    subcenter=I                 set sub-center to I
    packing=S                   set compression/packing to S
                                S=simple,complex1,complex2,complex3,jpeg (long form)
                                S=s,c1,c2,c3,j (short form)

To change the metadata, you can do

wgrib2 in.grb -set_metadata  meta -grib_out out.grb

The -set_metadata option is used for creating grib2 files. Note that both -set_metadata and the various -import options will change the output precision. Consequently the -import option should preceed the -set_metadatda option.

Note: only a subset of levels and ftime parameters is currently implemented. The -set_metadatda option does not support all metadata.

To format of the levels and ftime are the same was used by wgrib2 inventories.

See also: -set_ave, -set_date, -set_ftime, -set_lev, -set_scale, set_var,