[ncl-talk] different RMSE values calculated by NCL and CDO

[LI Qi]

Dear NCL community,


I would like to calculate spatial RMSE of simulations and observations.


the NCL function I use is:
rmse = dim_rmsd_n(obs, sim, (/1,2/))
where (/1,2/) represents the spatial dimensions lon,lat




while the CDO command is:
cdo sqrt -fldmean -sqr -sub sim.nc obs.nc rmse.nc


However, the CDO output (64.44424) is different from the NCL one (63.95646), and I couldn't figure out why.


Attached are the two .nc files (sim var=rain_tot(time, lat, lon); obs var=crain(time, lat, lon))


Any hint is much appreciated!


Best, 
Qi
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