NARR grid point data extraction

[Wesley Ebisuzaki]

Patrick Pyle wrote:
> Hi,
>
> I am interested in extracting specific grid point data values from the
> 32 km NARR GRIB dataset and place them into a text file.  I have used
> the gribscan utility to view the data and curious to know how to find
> where the actual 32 km grid points are on the map and how to take data
> values from a selection of grid points.  Can anyone point me in the
> right direction?
>
> Thanks for your help,
>
> Patrick
Patrick,

     NCEP tries to make available latitude and longitude GRIB files that
correspond to the various grids that are used at NCEP.
The fixed file that you need is at:

              ftp://ftp.cpc.ncep.noaa.gov/wd51we/NARR/rr-fixed.grb

Do not use the output grid fixed-file on the NARR home page because it
still points to an old file.

To get a list of the latitudes for the various grid points, type

-sh-2.05b$ wgrib -d 20 rr-fixed.grb -text -o lat.dat
20:2577616:d=79110800:NLAT:kpds5=176:kpds6=1:kpds7=0:TR=1:P1=0:P2=0:TimeU=1:sfc:anl:NAve=0

For the longitudes (west is negative), type

-sh-2.05b$ wgrib -d 19 rr-fixed.grb -text -o lon.dat
19:2384176:d=79110800:ELON:kpds5=177:kpds6=1:kpds7=0:TR=1:P1=0:P2=0:TimeU=1:sfc:anl:NAve=0

The first line of the lon.dat and lat.dat is the head showing the
dimension of the grid (349 x 277).
The the longitude/latitude of the next 349 x 277 grid are shown.

 From lon.dat and lat.dat, you can find the grid points of interest.
You'll then need a program (fortran, c, basic, perl)
along with wgrib to extract and make a text time series.


Of course, you can always use grads to extract the data and make a time
series.  If you don't mind the interpolation
errors, that would be the easiest.

          Wesley Ebisuzaki