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Re: Time Axis error

On Wed, 20 Mar 2002, Bruce W. Ford wrote:
> SET DATA "intraseasonal/feb97-z200a.nc"
> SET DATA "intraseasonal/jan97-z200a.nc"
> let z200ad = hgt[d=1]-hgt[d=2]
> Gives me:
> ***Note:  Ambiguous coordinates on T axis:
> HGT[d=1]-HGT[d=2]
> **Error:  Illegal limits:  HGT is not in the range
> T=01JAN
> Axis extremes are T+01-JAN  00:00

Hi Bruce,

It looks like the two files you're using have different time axes, and
Ferret doesn't know which time axis you want the result z200ad to be on.
You can resolve the ambiguity by regridding one of the arguments, e.g.

let z200ad = hgt[d=1,gt=hgt[d=2]@asn]-hgt[d=2]

That will force the first argument onto the January axis before the
subtraction.  You can read about the @ASN regridding transformation at

Hope that helps,


Andrew Wittenberg          Program in Atmospheric and Oceanic Sciences
andyw@splash.princeton.edu                        Princeton University

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