[gradsusr] Normalize GFS precipitation to 1hr

Wesley Ebisuzaki - NOAA Federal wesley.ebisuzaki at noaa.gov
Mon May 2 13:09:59 EDT 2016


The GFS will have hourly output up to 120 hours.  However, to remain
compatible with the older forecast files, the precip is accumulated for
6 hours before resetting the bucket.  You can get the hourly (or 3 hourly
for the forecast hour > 120) by

   cat  gfs.t06z.pgrb2.0p25.f??? |    \
   wgrib2 - -match APCP -set_grib_type c1 -ncep_norm apcp.grb

Line 1: takes all the hourly gfs forecasts:  gfs.t06z.pgrb2.0p25.f000,
,.., gfs.t06z.pgrb2.0p25.fNNN    and writes it stdout

Line2: wgrib2 -   (read grib file from stdin)
                        -match APCP   (only process APCP)
                        -set_grib_type c1   (write out in complex1 packing)
                        -ncep_norm apcp.grb    (make hourly and write to



On Mon, May 2, 2016 at 6:33 AM, Ivan Toman <ivtoman at inet.hr> wrote:

> Hello,
> As new GFS has 1hr output step, it would be nice to normalize
> precipitation amount in grib files to 1h. To do this I tried, after
> downloading gribs in 1h step:
> cat *.gfs.* > gfs.grib2
> wgrib2 gfs.grib2 -set_grib_type c1 -ncep_norm normalized_gfs.grib2

The problem is that -ncep_norm takes a specific format.  All the APCP
have to be grouped together.

> g2ctl -verf normalized_gfs.grib2 >n_gfs.ctl
> gribmap -i n_gfs.ctl
> Then open n_gfs.ctl in GrADS, however, it seems to me that precipitation
> is not being normalized correctly.
> Am I missing something?
> Is there any other way to get nice 1h precipitation steps in grib files
> or can you suggest GrADS way to do 1h precipitation without normalizing
> gribs first?
> Thank you,
> Ivan Toman
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> gradsusr at gradsusr.org
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