Re: [ferret_users] Opening identical datasets define axis that are shared

["Ansley C. Manke" <ansley.b.manke@xxxxxxxx>]

Hi Patrick,

Identical axes are shared as datasets are opened.  For them to be shared, they need to be identical in all respects including axis name, units, and coordinates. For your purposes it should be enough to just rename the first dataset's axis before opening the second set.

use http://vesg.ipsl.upmc.fr/thredds/dodsC/work_thredds/p86pasb/IPSLCM6/PROD/midHolocene/CM61-LR-H6k-03/MONITORING/files/ATM_t2m_global_prio_ave.nc

set axis/name=new_name `var,return=taxis

use http://vesg.ipsl.upmc.fr/thredds/dodsC/work_thredds/p86pasb/IPSLCM6/PROD/midHolocene/CM61-LR-H6k-02/MONITORING/files/ATM_t2m_global_prio_ave.nc

On 3/21/2019 8:03 AM, Patrick Brockmann wrote:

Hi ferreters,

I have encountered a problem when I open multiple identical datasets.

I can see that time axis are not defined for each dataset but shared.

It is a strategy.

But as a consequence, if I apply a change on a axis (for example a 10 days offset on the 1st one) then

other variables that share the time axis get this offset as well.

Is there a way to force ferret to define a unique time axis for each dataset ?

Below a simplified script that shows the problem.

!==============================================================================

cancel data/all; cancel var/all; cancel axis/all
 
use http://vesg.ipsl.upmc.fr/thredds/dodsC/work_thredds/p86pasb/IPSLCM6/PROD/midHolocene/CM61-LR-H6k-03/MONITORING/files/ATM_t2m_global_prio_ave.nc
use http://vesg.ipsl.upmc.fr/thredds/dodsC/work_thredds/p86pasb/IPSLCM6/PROD/midHolocene/CM61-LR-H6k-02/MONITORING/files/ATM_t2m_global_prio_ave.nc

let var=T2M_GLOBAL_PRIO[L=@SBX:120]

show axis `var[d=1], return=taxis`
show axis `var[d=2], return=taxis`

let tt = t[gt=`var[d=2],return=taxis`]
define axis/t/t0="`var[d=2],return=t0`"/units="`var[d=2],return=tunits`"/calendar="`var[d=2],return=cal`" `var[d=2],return=taxis` = tt + `10*24*60*60`

show axis `var[d=1], return=taxis`
show axis `var[d=2], return=taxis`

!==============================================================================

I get a note from ferret telling

Replacing definition of axis TIME_COUNTER
           *** NOTE: grid GOO1 used by data set ATM_t2m_global_prio_ave
           *** NOTE: Redefinition may alter apparent contents of data set
           *** NOTE: grid GOO2 used by data set ATM_t2m_global_prio_ave
           *** NOTE: Redefinition may alter apparent contents of data set

How could I do then to apply an offset on the 2nd dataset without modifying the 1st one ?

Thanks

Patrick

--
Data Analysis and Visualization Engineer / Project Manager
LSCE/IPSL, CEA-CNRS-UVSQ laboratory
LSCE - Climate and Environment Sciences Laboratory
IPSL - Institut Pierre Simon Laplace
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