[ncl-talk] eofunc giving empty eigenvalues

[Giorgio Graffino]

Dear NCL people,
I'm struggling at computing the EOFs of a zonal wind stress field. I'm always getting this warning from the eofunc functions:
 Warning! LAPACK routine returned eigenvalue <= 0.

 Setting it to zero...


I've seen that the original LAPACK's dspevx function sets a 1.e-6 threshold for computing EOFs; if there is a value below that threshold, zero EOFs are returned (https://github.com/yyr/ncl/blob/master/ni/src/lib/nfpfort/eof_scripps.f). I'm using the where function to set all values below 1.e-6 as fill values (something like taux = where(taux.le.1.e-6,taux at _FillValue,taux)) before the eofunc function is called, yet I'm getting the same warning and the same empty EOFs. Is there anything else I'm missing?
Thanks,Giorgio
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