Intercomparison of δ18O in precipitation simulated by Isotopic GCMs with GNIP Observation over the East Asia

Abstract

Using the isotope enabled ECHAM4, GISS E, HadCM3 and MUGCM GCMs, the spatial distribution of mean δ18O in precipitation, the mean seasonality (JJA-DJF) and the correlations of δ18O in precipitation with temperature and precipitation amount are analyzed. The simulation results reproduce well the stable isotopic features by the GNIP observations. Over the East Asia, the distribution of δ18O in precipitation is of marked latitude effect and altitude effect. The largest seasonality of δ18O in precipitation appears in the eastern Siberia controlled by cold high pressure, and the smallest one in the Western Pacific controlled by the subtropical high. The comparatively weak seasonality appears in middle latitudes where oceanic and continental air masses interact frequently. Temperature effect occurs mainly in mid-high-latitude and inlands. The higher the latitude is, the closer to inland is, and then the stronger the temperature effect is. Amount effect occurs mainly in low-mid latitudes and monsoon areas, with the strongest effect in low-latitude coasts or islands. A significant difference between simulations and observations is that the standard deviation of GCMs statistics is greater than that of GNIP statistics. On the contrary, as comparing parallelly time series at single station, the standard deviations of GCMs simulations is smaller than that of GNIP observations.