The Norwegian Climate Prediction model combines the Norwegian Earth System Model version 1 (medium resolution) with the Ensemble Kalman Filter data assimilation method. netcdf 4 format. Technical details: Production machine: Cray XE6 in Bergen (hexagon) Model source: projectEPOCASA-3: atmosphere=CAM4; ocean=MICOM; land=CLM; sea ice=CICE Horizontal resolution: atmosphere/land=1.9x2.5 degree; ocean/sea ice=~1 degree Output frequency: monthly + yearly run on 160 mpi tasks. Use : hybrid start from historical simulation 30 members (N20TREXTAERCN COMPSET) at 1950-01-15; which are initiazed from preindustrial run (N1850; starting date 1500:10:1790). Library: craype-barcelona, craype/2.2.1, cray-libsci/12.1.3, cray-mpich/6.0.2, cray-netcdf/4.3.2, cray-hdf5/1.8.13, pcp, coreutils-cnl). For the assimilation, we use the Detereministic Ensemble Kalman Filter (EnKF-MPI-TOPAZ_Yiguo_no_copy), with 30 members, localisation radius of 1 grid cell with no tapering (STEP); rfactor=2 and kfactor=2, inflation=1, MASK_LANDNEIGHBOUR=.true., aggregation method=.true. (Wang et al. 2016). The full state is updated (u,v,dp,temp,saln,uflx,vflx,outfox,vtflx,usflx,vsflx,pb,ub,vb,ubflx,vbflx,ubflxs,vbflxs,ubcors_p,vbcorhs_p,phi,sealv,ustar,buoyfl) 1 time level (e.g. temp from 1 to 53 and pb from 1 to 1). The observation error variance is inflated by a factor of 8 and gradually decreased over 5 assimilation cycles (5 months). The observations are the SST ensemble mean (10 members) from HadISST2.1.0.0, and the observation error variance is the ensemble spread. We assimilate SST monthly anomaly. The monthly climatology is calculated from the simulation with assimilation (free run) wrt to the period 1950-2009.