[gradsusr] Time: confused between grid vs. world coordinates

gilles delaygue gilles.delaygue at univ-grenoble-alpes.fr
Tue Jul 2 14:14:08 EDT 2019

Dear all, i’m using GrADS again after some years, and get confused with time coordinates. I’ve generated a netcdf file from a text CDL file containing a 2D lon-lat field with UNEVEN time steps. (My time is in unit of days since 1945-1-1, with irregular records.)
In a GrADS session, setting time as grid coordinate (eg, 'set t 100’) effectively displays the (in that case) 100th field record, but the corresponding time is set as 100 days since 1945-1-1 (world coordinate) and not as the 100th time value. (And conversely, if i set time as a world coordinate, eg, ’set time 12z1jan1946’, ie 366 days after the reference, the displayed field record is the 366th record and not the one corresponding to that date.)
I’am completely confused: did i make something wrong when generating my netcdf file, or should the time grid absolutely be even (and i need to define my records as station records)? 
Many thanks for your help!
Regards -gilles

IGE UGA Grenoble

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