Continuous monitoring of the isotopic composition of surface water vapor at Lhasa, southern Tibetan Plateau

The stable isotopes (818O and 8D) of water vapor are used to characterize continuous variations in large-scale and boundary-layer atmospheric processes. We presented continuous measurements of 818O in surface water vapor at Lhasa, southern Tibetan Plateau, from October 2018 to September 2019 to investigate how large-scale and local atmospheric processes influence variations in water vapor 818O at different time scales. The water vapor 818O measurements reveal different seasonal characteristics and diurnal patterns. At the seasonal scale, 818O exhibits a W-shape with two maxima in May-June and October as well as two minima in July-August and February. The diurnal variations in the water vapor 818O and meteorological data throughout the year present distinct occurrences of maxima and minima during different periods. We found that the significant seasonal variability is mainly associated with the transition between the Indian summer monsoon and the westerlies, which transport distinct moisture to the southern Tibetan Plateau. The local temperature, specific humidity and boundary layer height impact the diurnal variations in water vapor 818O to some extent with remarkable seasonal differences.