Re: [idvusers] Plotting views across the prime meridian using IDD GFS

Hi,

For GRIB files you can use PINGO (http://www.mad.zmaw.de/Pingo/pingohome.html), for example

for time subset:
grb selrec,1,100809 ../A2/EH5_OM_A2_1_TEMP2_1-146096.grb EH5_OM_A2_1_TEMP2_1-100809.grb

and for lat lon subset;
grb sellonlatbox,290,360,80,10 ./EH5_OM_A2_1_TEMP2_1-100809.grb ./EH5_OM_A2_1_TEMP2_1-100809_290-360-80-10.grb grb sellonlatbox,0,70,80,10 ./EH5_OM_A2_1_TEMP2_1-100809.grb ./EH5_OM_A2_1_TEMP2_1-100809_0-70-80-10.grb
rm EH5_OM_A2_1_TEMP2_1-100809.grb

but i don't know about GRIB2 support and CDO (Climate Data Operator).

For netcdf files NCO can modify the netcdf file as you want. The following PyNGL scripts helps to you,

import Nio
from Numeric import *
import os

# slab dimensions
os.system('rm nnrp.slab.nc')
os.system('ncks -d lon,330.0,80.0 -d lat,17.5,60.0 nnrp.nc nnrp.slab.nc')

# open netcdf file
nc = Nio.open_file("./nnrp.slab.nc", "rw")
lon = nc.variables['lon']

# fix dimension >> monotonic
for i in xrange (0,12):
       lon[i] = lon[i][0]-360.0

# close file
nc.close()

The os.system part of the code gets subset of the file and rest of the code correct 360 problem and generates monotonic dimension.

best

Ufuk Utku Turuncoglu
Istanbul Technical University
Informatics Institute

webmaster-IWC wrote:
Hi Dan,
I have not worked out how to directly reply to your question on the
forum, so I have done it this way.
I have had the same problem and I know the cause and a possible
solution, but the solution requires creating a regional subset of the
grib or NetCDF file.
The problem lies with the grib file starting from 0 - 359 and IDV not
able to join the two halves of the map together. If you can create the
grib file to start from -60 to 60 then this draws this Ok.
This was not a problem as software is available for grib 1 products to
create regional subsets is available, but the NCEP will be switching to
grib2 and that's where the my problem is.
Where I used to used GGRIB to create sub regions, this will not work for
grib2 products.
So if any programmers read this, I am in desperate need of a program
which will create sub regions of grib2 products complied for windows XP.
Ian Gooch

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