grb2owi

converter from grib2 to OWI format wind/pre files

Usage: grb2owi.sh gribfiles

Version 0.1

grb2owi converts grib2 files in standard NCEP projections to OWI files (221, 222) on an equidistant lonlat grid. It uses wgrib2 to extract pressure, u10 and v10 from a sequence of grib2 files, interpolate from the grib2 grid to the user-defined grid, write out each time step (snap) to OWI text files, and concatenate the results into consolidated 221,222 files.

Assumptions

• UVP records are in each grib2 file
• Each file contains only one time level (split them into parts if needed)
• The files are named in a sequence that represents strictly increasing times, such that the wildcard expansion of the name is in the proper time order;
• If this is NOT true, then the user must put the files in the correct order on the commandline explicitly, e.g., ... file1.grb2 file2.grb2 ...
• The default variable names looked for in the grib2 files are: PRES UGRD VGRD
• The variables'' vertical levels are assumed to be "mean sea level", "10 m above ground", and "10 m above ground", respectively.
• The default variable:level combinations are thus:
  --presname "PRES:mean sea level"
  --ugrdname "UGRD:10 m above ground"
  --vgrdname "VGRD:10 m above ground"

Options

--ugrdname : name of e/w wind speed variable in grib file (def="UGRD:10 m above ground")   
--vgrdname : name of n/s wind speed variable in grib file (def="VGRD:10 m above ground")   
--presname : name of MSL pressure variable in grib file (def="PRES:mean sea level")  
--lon1     : longitude of lower left corner of lonlat box (def=276)  
--nlon     : number of points in lon direction (def=100)  
--dlon     : longitude increment for interpolation (def=.0267)  
--lat1     : latitude of lower left corner of lonlat box (def=24)  
--nlat     : number of points in lat direction (def=100)  
--dlat     : latitude increment for interpolation (def=.0267)  

Outputs

f.221, f.222 in OWI format

Notes

• The grib interpolation process will convert longitudes to negative-west convention if lon1 > 0
• User should use wgrib2 to investigate grib grid so as to appropriately set equidistant grid parameters

Examples

1. Convert files matching wildcard to OWI, using default regular grid parameters:
   prompt> grb2owi.sh sfc_2016100620_*.grb2

2. Convert files matching wildcard to OWI, with 200 points in each direction, starting at lower-left corner == (278,22)
   prompt> grb2owi.sh --nlon 200 -nlan 200 -lon1 278 -lat1 22 sfc_2016100620_*.grb2

3. Convert three files explicitly named on the commandline, using defaults:
   prompt> grb2owi.sh file234.grb2 file9873.grb2 file1.grb2

4. Convert files using a non-default pressure variable:level:
   prompt> grb2owi.sh --presname="PRMSL:mean sea level" nam_2016100620_*.grb2

5. retrieve CFSR grib2 files and map to an OWI grid. Note that global CFSR files are on a gaussian T574 grid. Fortunately, wgrib2 can move between NCEP grids easily. prompt> sh cfsr2owi.sh --startdate "2015-01-01" --enddate "2015-02-15 5b. If you want to reprocess the grib2 files into OWI, perhaps you want to change the spatial resolution and have NOT deleted the cdas files, then pass cfsr2owi.sh the skipdownload argument: prompt> sh cfsr2owi.sh --skipdownload --startdate "2015-01-01" --enddate "2015-02-15

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Brian Blanton Brian_Blanton@Renci.Org Renaissance Computing Institute
Oct 2018