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Lambert conformal conic projection

Added by Semjon Schimanke almost 7 years ago

Hi!

I extracted some data from MARS at ECMWF. The data is stored in grib2 on a Lambert conformal conic projection. First, I got the impression that the CDOs cannot handle this kind of data, especially the grid description. However, know it seems to me they can! :-)
Could somebody please confirm that it is correct to change the grid to a curvilinear with cdo setgridtype,curvilinear. Thanks!

Some more details:
1) The grid description of the downloaded data:
sm_semsc@bi1:TEST$ cdo griddes TEST_T2m.grb #
  1. gridID 1 #
    gridtype = lcc
    gridsize = 319225
    xsize = 565
    ysize = 565
    originLon = 341.68
    originLat = 17.612
    lonParY = 8
    lat1 = 48
    lat2 = 48
    xinc = 11000
    yinc = 11000
    projection = northpole
    cdo griddes: Processed 1 variable ( 0.09s )
    sm_semsc@bi1:TEST$

2) Transformation to a curvilinear grid:
sm_semsc@bi1:TEST$ cdo -f nc setgridtype,curvilinear TEST_T2m.grb TEST_T2m_curvi.nc
cdo setgridtype: Processed 1596125 values from 1 variable over 5 timesteps ( 0.64s )
sm_semsc@bi1:TEST$

sm_semsc@bi1:TEST$ cdo griddes TEST_T2m_curvi.nc | less #
  1. gridID 1 #
    gridtype = curvilinear
    gridsize = 319225
    xname = lon
    xlongname = longitude
    xunits = degrees_east
    yname = lat
    ylongname = latitude
    yunits = degrees_north
    xsize = 565
    ysize = 565
    xvals = -18.3199997 -18.2337151 -18.1473618 -18.0609417 -17.9744511 -17.8878937
    -17.8012695 -17.7145748 -17.6278152 -17.540987 -17.454092 -17.3671284
    ...

To me, everything seems correct. However, I would be happy if somebody could confirm that the data is treated in the right way.

Moreover, I do actually have a "real" question. Assuming that the procedure above is correct for a scalar field as temperature, what about the wind field? Is there any rotation needed if I change the grid to a curvilinear grid?

Thanks for any help or comment,
Semjon


Replies (3)

RE: Lambert conformal conic projection - Added by Karin Meier-Fleischer almost 7 years ago

Hi Semjon,

can you upload a Lambert Confom Conic test file.

-Karin

RE: Lambert conformal conic projection - Added by Semjon Schimanke almost 7 years ago

Hi Karin,

please find an example file attached. It includes one time step of T2m.

Best regards,
Semjon

RE: Lambert conformal conic projection - Added by Uwe Schulzweida almost 7 years ago

The Lambert conformal conic projection is fully supported in CDO. "setgridtype,curvilinear" will change the projection coordinates to geographical coordinates. Only the coordinates will be changed!
There is no rotation needed for this coordinate transformation.

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