eof show different result depending on version

[jiwon-j]

hello,
i found that the result from xarray.Eof show the different result depending on the xarray version.
I'm curious what has been updated to produce different results.

the versions i compared are 1) 0.20.1 and 2) 2025.4.0

• All code is the same except for the xarray version.

< eof >

coslat = np.cos(np.deg2rad(refdata.coords["lat"].values))
wgts   = np.sqrt(coslat)[..., np.newaxis]
solver = Eof(refdata, weights=wgts)

refdata_eofs    = solver.eofs(neofs=3, eofscaling=0)
refdata_covs    = solver.eofsAsCovariance(neofs=3, pcscaling=0)
refdata_pcs     = solver.pcs(npcs=3, pcscaling=0)
refdata_varfrac = solver.varianceFraction()

i simply compared the two versions by using PC1 time series.

1. version 0.20.1
   

2. version 2025.4.0
   

the absolue values are same, but the signs are partialy mixed.

[dcherian]

Please report at https://github.com/xarray-contrib/xeofs/issues