Simultaneous monitoring of stable oxygen isotope composition in water vapour and precipitation over the central Tibetan Plateau
Abstract. This study investigated the daily δ18O variations of water vapour (δ18Ov) and precipitation (δ18Op) simultaneously at Nagqu on the central Tibetan Plateau for the first time. The data show that the δ18O tendencies of water vapour coincide strongly with those of associated precipitation. The δ18O values of water vapour affect those of precipitation not only on the same day, but also for the following several days. In turn, the δ18O values of precipitation also affect those of water vapour. Hence, there exists an interaction between δ18Ov and δ18Op, and the interaction decreases gradually with time. During the entire sampling period, the variations of δ18Ov and δ18Op at Nagqu did not appear dependent on temperature, but did seem significantly dependent on the joint contributions of relative humidity, surface pressure, and precipitation amount. In addition, the δ18O changes in water vapour and precipitation can be used to diagnose different atmospheric trajectories, especially the influences of the Indian monsoon and convection. Moreover, intense activities of the Indian monsoon and convection may cause the enrichment of δ18Op relative to δ18Ov 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.