Remapping on generic grid
Added by Paolo Davini over 8 years ago
Hi all,
I know that CDO does not allow remapping on generic grid. However, I am a bit puzzled because it should be theoretically possible in some specific circumstances (as the one I am experiencing).
I am working with LES simulations, which uses a "generic" grid which is actually regularly space in both x and y direction. It is not a "geo-referenced" grid - which I think is the original sin.
Here below the grid I am using, which is 256x256.
# # gridID 25 # gridtype = generic gridsize = 65536 xname = xt xunits = m yname = yt yunits = m xsize = 256 ysize = 256 xfirst = -2550 xinc = 20 yfirst = -2550 yinc = 20
Imagine you want to degrade it to a 128x128, with similar domain and doubled xinc,yinc.
# # gridID 25 # gridtype = generic gridsize = 16384 xname = xt xunits = m yname = yt yunits = m xsize = 128 ysize = 128 xfirst = -2550 xinc = 40 yfirst = -2550 yinc = 40
So I do
cdo remapbil,newgrid.txt filein.nc fileout.nc
As expected, I get an abort with "unsuported grid type". Well, is there a way to do such simple interpolation with CDO? Area weights are all the same and it should be easy to compute them.
I looked in the forum to find any suggestions to circumvent this problem, but I did not end to anything.
Any opinions, even negative, are greatly appreciated. I can attach a sample file if you want.
Thanks!
Paolo
Thanks
Replies (7)
RE: Remapping on generic grid - Added by Uwe Schulzweida over 8 years ago
Hi Paolo,
You are right, this is theoretically a very simple case for the remapping. Unfortunately the remapping in CDO needs at least some refactoring to support this simple grid because some search routines are only available on the 3D sphere.
But CDO has a 2nd implementation of the bilinear interpolation. This undocumented operator is called intgridbil. I have added support for this grid to this operator. This feature is available in the latest CDO prerelease (https://code.zmaw.de/projects/cdo/files).
Cheers,
Uwe
RE: Remapping on generic grid - Added by Paolo Davini over 8 years ago
Hi Uwe,
many thanks for the reply. I see the point.
I tried the operator you suggested me, and actually I get a different error, which is somehow encouraging ;-)
cdo intgridbil,grid.txt filein.nc out.nc cdo intgridbil (Abort): Interpolation of generic data unsupported!
Thus now the problem seems the data, not the grid, which is actually confusing me. Perhaps it can be fixed changing some attributes of the netcdf file, but to me it is not clear how.
I am running with CDO 1.6.8, and I tested also with the 1.6.9 on a local machine, with the same issue. Are they recent enough?
I attach two sample files for sake of reproducibility.
RE: Remapping on generic grid - Added by Uwe Schulzweida over 8 years ago
Hi Paolo,
I have added the support for the "generic" to the operator intgridbil yesterday. To test this feature you need the latest CDO prerelease cdo-current.tar.gz from https://code.zmaw.de/projects/cdo/files.
Cheers,
Uwe
RE: Remapping on generic grid - Added by Paolo Davini over 8 years ago
Sorry Uwe,
I do not know why I read "latest releases" instead of "latest prerelease". I will try it in the next days and let you know! Thanks for the help!
Cheers,
Paolo
RE: Remapping on generic grid - Added by Paolo Davini over 8 years ago
Hi Uwe,
Thanks a lot! I tested it this morning and at first glance it is working fast and fine. I will probably do some further comparisons with other softwares soon.
On the left of the attached file you have "original" (256x256 points) and on the right the "interpolated" (128x128).
I found out I have some issues with the vertical interpolation of those grids as well, I will be probably back on this on a separated post!
Best,
Paolo
| intgridbil.png (1.21 MB) intgridbil.png |
RE: Remapping on generic grid - Added by Zichong Chen over 7 years ago
Hi Paolo,
I ran into the same problem like you did, and I downloaded your netcdf file and grid text and tried to run it under CDO version 1.8.0. However, I got negative information here:
cdo intgridbil (Abort): Interpolation of generic data unsupported!
Do you have any suggestions bases on your experience? Thanks in advance.
Best,
Zichong
RE: Remapping on generic grid - Added by Paolo Davini over 7 years ago
Hi Zichong,
I have just checked, with cdo 1.8.0 and the test files above it works fine for me. Please note that my grid.txt file is a bit crooked, it should read xinc=40 and yinc=40 otherwise the interpolation is not complete but only on a subdomain.
However it works in both cases. Here below my cdo properties.
Cheers,
Paolo
Climate Data Operators version 1.8.0rc7 (http://mpimet.mpg.de/cdo)
Compiled: by pd2507 on watson (x86_64-unknown-linux-gnu) Feb 9 2017 11:20:07
Compiler: gcc -g -O2 -fopenmp
version: gcc (GCC) 6.1.0
Features: DATA PTHREADS OpenMP45 HDF5 NC4/HDF5/threadsafe SZ SSE2
Libraries: HDF5/1.8.15
Filetypes: srv ext ieg grb1 nc1 nc2 nc4 nc4c
CDI library version : 1.8.0rc7 of Feb 9 2017 11:18:51
CGRIBEX library version : 1.7.6 of Dec 20 2016 19:55:24
NetCDF library version : 4.3.3.1 of Feb 9 2017 03:38:44 $
HDF5 library version : 1.8.15 threadsafe
SERVICE library version : 1.4.0 of Feb 9 2017 11:18:31
EXTRA library version : 1.4.0 of Feb 9 2017 11:18:24
IEG library version : 1.4.0 of Feb 9 2017 11:18:28
FILE library version : 1.8.2 of Feb 9 2017 11:18:25