Comparison of GCM-simulated isotopic compositions of precipitation in arid central Asia

The isotope-equipped GCMs (general circulation models) are useful tools to investigate the isoscape in precipitation and water vapor, especially for the regions without enough in-situ observations. To study the spatial distribution and seasonal variation of precipitation isotopic composition in arid central Asia, several isotope-equipped GCMs are applied, and the long-term observations in two stations are used to verify the GCM-simulated results. Generally, seasonality of isotopic composition can be well simulated in each GCM, and the values of δ18O in precipitation are larger in summer months (from April to October) and lower in winter months (from November to March). Higher latitude usually shows lower values of δ18O in precipitation, and lower latitude has higher values. The values of δ18O are relatively low in the eastern section, and higher in the western section. Among these simulations, ECHAM is good at describing the isotopic composition in the study region, which can be seen from the mean absolute error (MAE) and root-mean-square error (RMSE). The ECHAM-derived values of δ18O in precipitation positively correlate with the observed series, and the correlation coefficient based on ECHAM is the largest among these GCMs.