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Re: Strange zonal mean difference plotting



Hi Billy,

Thanks for the email. We've verified the data is ok, it's simply that one netcdf file has a small rounding error on the longitude values which is making the difference. I wrote a small f90 program to compute the zonal mean difference plot using data from the netcdf files and once on the correct grid ferret is doing the right job. My GrADS guru is still puzzling over why GrADS produces the wrong plot and does it silently.

Thanks for the tip about plot/line/sym=27.

Regards,
Glenn


Hi Glenn -

I agree with you that getting an incorrect plot with
no indication of error is the worst fear. What if it
got published? The only solution is to do a calculation
several different ways, which is ordinarily the case
anyway as you seek to understand a result.

With respect to your example, I have no definitiev answer,
but just a suggestion: rather than work with the entire
grid, work with a single latitude (perhaps writing out
two new netcdf files at the same latitude). Often the
details behind a phenomena become clearer when plotted
with gridpoint dots (plot/line/sym=27) than when trying
to compare color-fill plots by eye.

The fact that GrADS is also making incorrect plots would
make me look very closely at the data in those files, rather
than at the software .....

Good luck.

Billy K


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