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HOME > Monitoring_and_Data > Oceanic and Atmospheric Data > Reanalysis: Atmospheric Data > wgrib2-wind_dir

wgrib2: -wind_dir


The -wind_dir option takes the zonal and meridional winds, computes the wind direction and writes it out in grib format. The results is in degrees where 0 degrees is a wind from the north and 90 degrees is a wind from the east. For this option to work, (1) the zonal and meridional winds must be earth relative (not grid relative winds) and (2) the meridional wind must follow the corresponding zonal wind for that level, time and forecast hour. (Condition 2 is the same restriction as for the -wind_speed option. If the U and V in your grib file do not have this order, the file must be sorted. However, many NCEP forecast files already have this order.

The winds need to be earth relative. The -new_grid option can convert between earth and grid relative winds.

You can save computer time by using the -match option to restricting the decoding of records to U and V.


-wind_dir output_grib_file

   Comment: the -wind_speed option can write to the same file as -wind_dir


$ wgrib2 gep19.t00z.pgrb2af180 -wind_dir wind.grb -wind_speed wind.grb -match "(UGRD|VGRD)"
4.1:86046:d=2009060500:UGRD:200 mb:180 hour fcst:ENS=+19
4.2:86046:d=2009060500:VGRD:200 mb:180 hour fcst:ENS=+19
8.1:226831:d=2009060500:UGRD:250 mb:180 hour fcst:ENS=+19
8.2:226831:d=2009060500:VGRD:250 mb:180 hour fcst:ENS=+19

$ wgrib2 wind.grb
1:0:d=2009060500:WDIR:200 mb:180 hour fcst:ENS=+19
2:97922:d=2009060500:WIND:200 mb:180 hour fcst:ENS=+19
3:179554:d=2009060500:WDIR:250 mb:180 hour fcst:ENS=+19
4:277476:d=2009060500:WIND:250 mb:180 hour fcst:ENS=+19

See also: -match, -wind_speed

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Page last modified: Feb 4, 2013
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