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Converting WRF lambert conformal to latlon grid

Added by Litta Arakkal 4 months ago

Hi,
I was converting WRF output for the region between latitudes -60 to 20 and longitudes -160 to 60, using bilinear interpolation at a resolution of 2 km. The conversion worked properly for domains over the US and Europe. However, I encountered issues with domains in the Southern Hemisphere.
I have attached the datasets and figures. Please check them and suggest a solution.
Output grid specification
  1. Define 0.02-degree global lat-lon grid
    #grid_description = """
    grid_description = """\
    gridtype = lonlat
    xsize = 7511
    ysize = 4001
    xname = lon
    xlongname = "longitude"
    xunits = "degrees_east"
    yname = lat
    ylongname = "latitude"
    yunits = "degrees_north"
    xfirst = -90.00000
    xinc = 0.02
    yfirst = -60.00000
    yinc = 0.02
    """
    UV10.grb2 is the original data. test.grb is the converted data
Download all files
UV10.grb2 (2.18 MB) UV10.grb2 WRF output
Screenshot 2025-07-22 at 17.15.52.png (278 KB) Screenshot 2025-07-22 at 17.15.52.png WRF output plot
check_wind.png (110 KB) check_wind.png converted data plot
test.grb (24.9 MB) test.grb Converted data

Replies (6)

RE: Converting WRF lambert conformal to latlon grid - Added by Uwe Schulzweida 4 months ago

The orientation of the latitude parameters for the lambert projection in the southern hemisphere is unfortunately not correct with GRIB2 data. We will fix this problem in the next CDO release 2.5.3.
This problem can only be solved by setting the correct projection parameters with setprojparams:

cdo remapbil,<targetgrid> -setprojparams,'+proj=lcc +a=6371000 +lon_0=344.533984 +lat_0=-22.432 +lat_1=-22.432 +lat_2=-22.432 +x_0=7534717.40492831 +y_0=5719446.03519481' UV10.grb2 result

RE: Converting WRF lambert conformal to latlon grid - Added by Litta Arakkal 4 months ago

Thank you so much for your support!
This command is working.

check_wind.png (134 KB) check_wind.png

RE: Converting WRF lambert conformal to latlon grid - Added by Litta Arakkal about 2 months ago

Hi,
Thank you for your support!
I am facing same issue for converting Australian domain.
I was WRF output for the region between latitudes -45 to 8 and longitudes 100 to 170, using bilinear interpolation at a resolution of 2 km.
I am attaching my dataset (gr2 file).Please help me to solve this issue.
  1. Define 0.02-degree global lat-lon grid
    grid_description = """
    gridtype = lonlat
    xsize = 3511
    ysize = 2651
    xname = lon
    xlongname = "longitude"
    xunits = "degrees_east"
    yname = lat
    ylongname = "latitude"
    yunits = "degrees_north"
    xfirst = 100.00000
    xinc = 0.02
    yfirst = -45.00000
    yinc = 0.02
    """
2025091705_000.gr2 (3.74 MB) 2025091705_000.gr2

RE: Converting WRF lambert conformal to latlon grid - Added by Litta Arakkal about 2 months ago

Sorry. I couldn't upload the data properly.
Please check attached data

2025091705_000.gr2 (96.1 MB) 2025091705_000.gr2

RE: Converting WRF lambert conformal to latlon grid - Added by Uwe Schulzweida about 2 months ago

Here, the projection parameters must also be specified with setprojparams:

cdo remapbil,<targetgrid> -setprojparams,'+proj=lcc +a=6371000 +lon_0=133.242008 +lat_0=-30.145 +lat_1=-30.145 +lat_2=-30.145 +x_0=4230670.54711589 +y_0=1840338.2951872' infile outfile

RE: Converting WRF lambert conformal to latlon grid - Added by Litta Arakkal about 2 months ago

Thank you so much for your support!. IT is working perfectly.

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