Accurate reproduction of daily to interannual variations of stable water isotopes using Iso- GSM and spectral nudging technique

This study incorporates the stable water isotopes into NCEP/ECPC's global spectral model in a manner similar to other isotope AGCMs. In addition, a newly developed spectral nudging technique (Yoshimura et al., 2007) is used, which allows to reproduce more actual spatial and temporal distribution of water and isotopes distributions. Divergence, vorticity, and temperature in NCEP/NCAR Reanalysis 2 data are the base fields that are nudged for more than 1000 km scales. Specific humidity remains unnudged in order to close the water budget. A T62L28 large-scale nudging simulation for 1979-2006 has now been simulated and the results show much more realistic precipitation isotope variations in comparison to an unnudged (free-forecast) simulation. Those simulation results with 3-dimensional structure of water isotopes are directly comparable with any occasional observations, in contrast to previous isotopic AGCMs, which are only usable for climatologic analyses.