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Generation weights between two SCRIP grids

Added by Vladimir Vovo almost 12 years ago

Hello!
I am trying to build weights between two SCRIP grids.
Files contain only grids, no data.
The quiestion is - how can i explain it to CDO, like this:

cdo genbil,grid1.nc grid2.nc w.nc

Instead of:

cdp genbil,grid1.nc ifile w.nc.

Because at initialization i have no data 'ifile', i have only SCRIP-grids.

Thanks.


Replies (2)

RE: Generation weights between two SCRIP grids - Added by Uwe Schulzweida almost 12 years ago

You have to create a temporary data field, e.g. with the operator random or const:

cdo genbil,grid1.nc -random,grid2.nc w.nc
cdo genbil,grid1.nc -const,1,grid2.nc w.nc

RE: Generation weights between two SCRIP grids - Added by Vladimir Vovo almost 12 years ago

Thanks, it helps. But than very strange thing happened..

I decided to rewrite my SCRIP weights generation(using original Fortran90 package), because CDO is much convenient.
I decided to compare results. And there are absolutely different!

First of all, I noticed strange thing - CDO 'gencon' change fields of source grid - for example imask field is different for source grid and for result weights file.
And as a result - I have different remap matrix.

I made test grids in CDO-SCRIP and original SCRIP formats(the same, but arrays are unrolled to vectors).

Build weights with command:
cdo gencon,grid2_cdo.nc -const,1,grid1_cdo.nc w_cdo.nc

You can see, that, for example, src_grid_center_lat is different for w_cdo.nc and grid1.nc.

Help me to understand it, please.

Download all files
grid1_cdo.nc (66.5 KB) grid1_cdo.nc
grid2_cdo.nc (9.05 KB) grid2_cdo.nc
grid1_scrip.nc (76.7 KB) grid1_scrip.nc
grid2_scrip.nc (19.3 KB) grid2_scrip.nc
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