Moisture Sources and Transport Paths during the Summer Heavy Rainfall Events in the Three-River-Headwater Region of the Tibetan Plateau

The moisture sources, transport paths and the quantitative moisture contribution of each source region and path of the South-West, West, North-East and South-East heavy rainfall types in the Three-River-Headwater region (TRHR) of Tibetan Plateau (TP) in summer are tracked, calculated and compared using the FLEXPART model. The results show that: the southern TP and the local target region of TRHR contribute the most moisture to the four types of precipitation. In addition, the northern TP is the third predominant moisture source region to the South-West and West rainfall types, which are distributed in the west of TRHR. Nevertheless, the third critical source region of the North-East and South-East rainfall types, which occur in the east of TRHR, is the eastern areas outside the TP. Four kinds of rainfall events have four identical moisture transport paths: Southern short-distance path, Southern long-distance path, Southwest path and Northwest path. The Southern short-distance path contributes the most moisture to the South-West (24.2%), West (19.8%) and South-East (15.9%) rainfall types, the second most moisture of which respectively comes from the Northwest path, Southwest path and Southeast path. In addition, the Southern short-distance path and Southwest path are the most active moisture transport channels of the three types of precipitation (more moisture trajectories are transported through these two paths). The moisture of North-East rainfall type is primarily contributed by the East path (26.0%) and the Northwest path (18.2%), and the most active moisture transport channels are the East path (21.9%) and the Southern long-distance path (19.9%).