Characteristics of Water Vapor Transport during the Winter/Summer Monsoon Periods in the Yarlung Zangbo Grand Canyon Region and Its Relationship with Precipitation in the Three-River Source Region

The Yarlung Zangbo Grand Canyon region (YZGC) is an important water vapor transport channel on the Qinghai-Xizang Plateau, and the water vapor transport of the YZGC has an important impact on the weather and climate of the plateau.Based on the ERA5 reanalysis data and CN05.1 precipitation data from 1986-2021, this paper analyzes the water vapor transport characteristics of the YZGC during the summer monsoon and winter monsoon periods and studies its relationship with precipitation in Three-River Source Region (TRSR) during the plateau summer monsoon period.The results showed that: (1) The precipitation in the YZGC was more in the southeast and less in the northwest and showed an increasing trend in time, and the increase in the summer monsoon period was greater than that of the annual average and the winter monsoon period.The water vapor flux of the YZGC mainly comes from the southwest water vapor transport from the Indian Ocean to the Bay of Bengal, followed by the westerly water vapor transport from the southern branch of the mid-latitudes.(2) The south and west boundaries of the YZGC are the water vapor input boundaries throughout the year, and the east and north boundaries are the water vapor output boundaries, and the water vapor transport flux during the summer monsoon is stronger than that during the winter monsoon period.The YZGC is a positive area of net water vapor flux, and the net water vapor income shows a significant decreasing trend.(3) The low-level 1000~600 hPa originates from the Indian Ocean to the Bay of Bengal and the western Pacific Ocean, and the water vapor transport enters the plateau from the southern boundary of the YZGC, and the southern boundary is the main boundary of water vapor input.The upper layer is 600~300 hPa, and the middle and high latitudes are significant westerly water vapor transport, and the water vapor is mainly imported from the western boundary and exported from the eastern boundary.(4) There is a significant positive correlation between the water vapor flux of the YZGC and the precipitation in the central and eastern parts of the TRSR during the summer monsoon.Anomalous southeast water vapor transport from the Bay of Bengal, as well as anomalous southwest water vapor transport from the northern Bay of Bengal and the southwestern side of the plateau, enters through the western and southern boundaries of the YZGC, providing ample moisture to the central and eastern parts of the TRSR.The upward motion of this water vapor in the central and eastern TRSR leads to increased precipitation.