Introduction

The option -new_grid requires that the grib file be processed in a certain order. When vector fields are encountered, the specifications are that the U field must be followed by the corresponding V field. (The -new_grid implementation allows any number of scalars to in between the U and corresponding V fields.) If you do not follow the specification, some U or V fields may not be interpolated.

Regridding grib files by the -new_grid is very common, and a technique have been developed to speed up this task. Basically you put scalar fields in its own grib message, and corresponding vector fields in their own grib message (U and V are in submessages). Then you can regrid each grib message independantly. If you have N cores, you run N copies of wgrib2 that regrids 1/N of the file. The -new_grid_order is designed to put the data in this structure.

The option -new_grid_order rearranges the file so that the fields follow the specification for use by -new_grid_order. Note that the order depends on the fields that are specified as vectors by the -new_grid_vector option. The output of -new_grid_order puts the U and corresponding V grib message into the same grib message, like -submsg_uvr. The vector fields that cannot be pair with the corrsponding U or V fields are written to a secondary file.

Usage

-new_grid_order GRIB_A GRIB_B
                GRIB_A is a grib output file with data in order compatible with -new_grid
                GRIB_B is a grib output file with data that cannot be processed by -new_grid
                   because corresponding U or V fields were missing

Example

$ wgrib2 gep19.badorder -new_grid_winds earth -new_grid ncep grid 3 test.grb
1:0:d=2009060500:HGT:200 mb:180 hour fcst:ENS=+19
2:70707:d=2009060500:UGRD:200 mb:180 hour fcst:ENS=+19
3:111348:d=2009060500:TMP:200 mb:180 hour fcst:ENS=+19
-new_grid: VGRD doesn't pair with previous vector field, field ignored
4:137484:d=2009060500:VGRD:250 mb:180 hour fcst:ENS=+19
5:182284:d=2009060500:RH:200 mb:180 hour fcst:ENS=+19
6:211191:d=2009060500:VGRD:200 mb:180 hour fcst:ENS=+19
7:254630:d=2009060500:HGT:250 mb:180 hour fcst:ENS=+19
8:325988:d=2009060500:TMP:250 mb:180 hour fcst:ENS=+19
9:351022:d=2009060500:UGRD:250 mb:180 hour fcst:ENS=+19
10:393024:d=2009060500:RH:250 mb:180 hour fcst:ENS=+19
11:424624:d=2009060500:HGT:500 mb:180 hour fcst:ENS=+19
-new_grid: last field UGRD was not interpolated (missing V)

(failed, U and V are not in the proper order)

$ wgrib2 gep19.badorder -new_grid_order - junk | \
   wgrib2 - -new_grid_winds earth -new_grid ncep grid 3 test.grb
1:3:d=2009060500:HGT:200 mb:180 hour fcst:ENS=+19
2:70820:d=2009060500:TMP:200 mb:180 hour fcst:ENS=+19
3:97067:d=2009060500:RH:200 mb:180 hour fcst:ENS=+19
4.1:126028:d=2009060500:UGRD:200 mb:180 hour fcst:ENS=+19
4.2:126028:d=2009060500:VGRD:200 mb:180 hour fcst:ENS=+19
5:210051:d=2009060500:HGT:250 mb:180 hour fcst:ENS=+19
6:281464:d=2009060500:TMP:250 mb:180 hour fcst:ENS=+19
7.1:306553:d=2009060500:UGRD:250 mb:180 hour fcst:ENS=+19
7.2:306553:d=2009060500:VGRD:250 mb:180 hour fcst:ENS=+19
8:393299:d=2009060500:RH:250 mb:180 hour fcst:ENS=+19
9:424954:d=2009060500:HGT:500 mb:180 hour fcst:ENS=+19

(worked)