Simultaneous monitoring of stable oxygen isotope composition in water vapour and precipitation over the central Tibetan Plateau

This study investigated daily delta 18O variations of water vapour ( delta 18Ov) and precipitation ( delta 18Op) simultaneously at Nagqu on the central Tibetan Plateau for the first time. Data show that the delta 18O tendencies of water vapour coincide strongly with those of associated precipitation. The delta 18O values of precipitation affect those of water vapour not only on the same day, but also for the following several days. In comparison, the delta 18O values of local water vapour may only partly contribute to those of precipitation. During the entire sampling period, the variations of delta 18Ov and delta 18Op at Nagqu did not appear dependent on temperature, but did seem significantly dependent on the joint contributions of relative humidity, pressure, and precipitation amount. In addition, the delta 18O changes in water vapour and precipitation can be used to diagnose different moisture sources, especially the influences of the Indian monsoon and convection. Moreover, intense activities of the Indian monsoon and convection may cause the relative enrichment of delta 18Op relative to delta 18Ov at Nagqu (on the central Tibetan Plateau) to differ from that at other stations on the northern Tibetan Plateau. These results indicate that the effects of different moisture sources, including the Indian monsoon and convection currents, need be considered when attempting to interpret paleoclimatic records on the central Tibetan Plateau.