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

摘要

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 coincidestrongly with those of associated precipitation. The δ18O values ofprecipitation affect those of water vapour not only on the same day, but alsofor the following several days. In comparison, the δ18O values oflocal water vapour may only partly contribute to those of precipitation.During the entire sampling period, the variations ofδ18O_v and δ18O_p at Nagqu did notappear dependent on temperature, but did seem significantly dependent on thejoint contributions of relative humidity, pressure, and precipitation amount.In addition, the δ18O changes in water vapour and precipitationcan be used to diagnose different moisture sources, especially the influencesof the Indian monsoon and convection. Moreover, intense activities of theIndian monsoon and convection may cause the relative enrichment ofδ18O_p relative to δ18O_v at Nagqu (onthe central Tibetan Plateau) to differ from that at other stations on thenorthern Tibetan Plateau. These results indicate that the effects ofdifferent moisture sources, including the Indian monsoon and convectioncurrents, need be considered when attempting to interpret paleoclimaticrecords on the central Tibetan Plateau.