Forums

Hi.

So I wanted to add a new topic, but the site says I'm not allowed to do that.

Help?

Thanks

Same here. How I can plot a sub-selected variable from a GRIB file that is comprised of many other variables ?

Hi Songhan,

(I can't create a new topic either)

I don't have a Magics answer for you but will make a suggestion using Metview:

I use Metview macros in general for plotting. Most GRIB I plot are in files with more than one GRIB record. I use the following macro code to pick the GRIB record (parameter-number/level-type/level) I want to plot. It might be possible to translate this for use in Magics python/magml/...

...
fcgrib = read  ( filename )
#
## filter fcgrib here
#
getpar=grib_get_long(fcgrib, 'indicatorOfParameter')
if type(getpar) = "string" then
  par=nil
  par=par&[getpar]
else
  par=getpar
end if
gettyp=grib_get_long(fcgrib, 'indicatorOfTypeOfLevel')
if type(getpar) = "string" then
  typ=nil
  typ=typ&[gettyp]
else
  typ=gettyp
end if
getlev=grib_get_long(fcgrib, 'level')
if type(getlev) = "string" then
  lev=nil
  lev=par&[getlev]
else
  lev=getlev
end if
print (" harmoniePlot:: GRIBs found = " & count(par))
pltgrb=1
for i = 1 to count(par) do
  if  par[i] = parsel and typ[i] = typsel and lev[i] = levsel then
    pltgrb=i
    print (" harmoniePlot:: GRIB found at " & i)
  end if
end for
plot ( display_window[1], fcgrib[pltgrb])
...

Hi Songhan, and thanks for your comment Eoin!

Again, a reply that uses Metview - depending on how similar your GRIB files are to the ones archived at ECMWF, Metview's Grib Filter module can give an easy way to do it:

all_data = read("/path/to/data.grb")

# filter Temperature at 1000hPa
filtered_data = read(
    levelist : 1000,
    param    : "t",
    data     : all_data
    )

plot(filtered_data)

This does not work with all non-ECMWF data though.

Outside of Metview, perhaps the GRIB_API tool grib_filter can do what you want, i.e. to filter out just the fields you want to plot.

Best regards,

Iain

Thanks for the replies!

I am afraid that the creation of topics is limited to people with write access to the wiki. But do drop an email to software.support@ecmwf.int and we can either create the topic for you or to answer the question directly

Daniel

Hello,

I want to plot wind from grib for forecast analysis but when i drag wind ploting icon and drop it on display window it doesn't work, please help me.