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

Abstract. This study investigated daily δ¹⁸O variations of water vapour (δ¹⁸O_v) and precipitation (δ¹⁸O_p) simultaneously at Nagqu on the central Tibetan Plateau for the first time. Data show that the δ¹⁸O tendencies of water vapour coincide strongly with those of associated precipitation. The δ¹⁸O values of precipitation affect those of water vapour not only on the same day, but also for the following several days. In comparison, the δ¹⁸O values of local water vapour may only partly contribute to those of precipitation. During the entire sampling period, the variations of δ¹⁸O_v and δ¹⁸O_p 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 δ¹⁸O 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 δ¹⁸O_p relative to δ¹⁸O_v 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.