Quantitative identification of moisture sources over the Tibetan Plateau: spatial distributions and temporal variabilities

Abstract The imbalanced hydrological cycles and water resource instability over the Tibetan Plateau (TP) are a topic of wide concern. Moisture sources affected by large-scale circulations are the main controls of precipitation and water resource distributions; as such, the quantitative identification of moisture sources is key to the changes in precipitation or water-related environments, further aids efficient water management over the TP and in downstream regions of Asia. In this study we primarily identified the spatial distributions and temporal variabilities of TP’s varied moisture sources, using Hysplit modeling and spatially dense precipitation isotopes (δ 18 O). Results showed that: (1) moistures from the Westerlies (West), the western arm of Indian Summer Monsoon (ISM) (ISM1), the eastern arm of ISM (ISM2), and the inner TP are the TP’s main moisture sources, with highest proportional contributions being >70%, ~40%, >80%, and ~10–20% at northwest, southwest, southeast sectors of the study area, and the central TP region; (2) each moisture has its own region where it predominates, and shows specific trends during 1951–2020 (West-northwest sector-increase, ISM1-southwest sector-increase, ISM2-southeast sector-decrease, TP-central TP region-increase); (3) each of the moisture proportions and their temporal trends varied with different days of back trajectories (days 02-04-06-08-10), while their spatial patterns are similar; and (4) when verifying the modeled moisture proportions, precipitation δ 18 O is positively correlated or co-vary with dry sources such as the West or TP moisture, and inversely for humid ISM (ISM1 or ISM2) moisture. This work will improve our understanding of moisture-related hydrological, meteorological, and ecological studies in the ‘Asian Water Tower’ region.