Introduction

The -import_grib_fs option sets the file pointer to the beginning of the file, and reads sequentially until it finds a record that matches the search string. It like a -if_fs for reading a grib file.

The option -import_grib reads the input file sequentially. The -import_grib_fs option allows you select the field to read.

Usage

-import_grib_fs STRING data.grb	     reads a grib message that matchs STRING from file data.grb
				     the match is by fixed string, not regular expression
                                     -g2clib 2 is not supported
                                     conversion to we:sn and we:ns is supported
                                     starts at the beginning of the file
				     reads sequentially
                                     -not and -match do not affect -import_grib
                STRING               this is a subset of the match inventory (see -match_inv)
		                     starting with d=YYYYMMDDHH
                data.grb             grib file for reading by -import_grib_fs
Note: grid size (if it can be determined) must match the current grid.

Example 1

#!/bin/sh
#
# ave two Z500 fields from totally different systems (CORe, CFS)
#
# Step 1, convert to same grid
# Step 2, use -import_grib_fs (v3.0.0+) to read the field
#         use -rpn to average the two fields
#         change center to unknown because the metadata is not descriptive
#
# Note: for Step 2,
#        -match ":d=2000010100:HGT:500 mb:"  is not needed
#        -import_grib_fs "d=2000010100:HGT:500 mb:anl:"  file2.grb
#          can be replaced by -import_grib file2.grb
# I made the code more complicated because if file1 and file2 were already on
# same grid, you can avoid Step 1.

file1=/cpc/cfsr/reanalyses/corefv3/ens_mean/3hr/pgb/2000/01/pgb_2000010100_ensmean
file2=/cpc/cfsr/archive/6hr_h/pgb.g2/2000/01/pgb.2000010100.g2

# Step 1
wgrib2 $file1 -match ":d=2000010100:HGT:500 mb:" -new_grid_winds earth -new_grid ncep grid 3 file1.grb
wgrib2 $file2 -match ":d=2000010100:HGT:500 mb:" -new_grid_winds earth -new_grid ncep grid 3 file2.grb
echo "\n\n"

# Step 2
wgrib2 file1.grb -match ":d=2000010100:HGT:500 mb:" -rpn "0.5:*:sto_0" \
   -import_grib_fs "d=2000010100:HGT:500 mb:anl:"  file2.grb \
   -rpn "0.5:*:rcl_0:+" -set_center 255 -grib_out ave.grb
exit 0

See also: -import_grib,