The Characteristics of Water Vapor Transport and Potential Sources of the Abnormal Summer Rainfall in Sanjiangyuan Region

Abstract

As the source of the three major rivers of Yangtze River， Yellow River and Lancang River in China， Sanjiangyuan （SJY） and its water vapor source and transportation have an important impact on the weather and climate in the downstream area.According to the summer precipitation data in the Sanjiangyuan area from 1994 to 2019， the precipitation in July showed multiple positive and negative anomaly exchange characteristics.The strongest positive anomaly was in 2012 （+1290 mm）， and the strongest negative anomaly is 2015 （-802 mm）.In this study， the FLEXPART model based on the Lagrangian method was used to simulate this abnormal precipitation period.All the air parcels that reached the source area of the target area during the study period were traced backward， focusing on the analysis of the water vapor transport characteristics and potential source of water vapor of SJY.Besides， the contribution of different water vapor sources to the precipitation of SJY was also evaluated.The results show that the water vapor transmission channels of SJY were mainly divided into the north and the south paths.During the period of positive anomalous precipitation， air parcels mainly transported from the north， west and south of the Qinghai-Xizang Plateau into SJY through the south path.While during the period of negative precipitation anomaly， air parcels mainly transported from the north side of the Qinghai-Xizang Plateau to SJY through the northern path.When the precipitation of SJY was smaller， the southern branch's transport was weaker and the northern path's transport was stronger.Among the potential water vapor sources of SJY， the most important contribution to the precipitation in SJY was on the northern side of the Qinghai-Xizang Plateau， followed by the western side of the Qinghai-Xizang Plateau and the local area， as well as the southern side of the Qinghai-Xizang Plateau， the Arabian Sea and the Bay of Bengal.The contribution of the northern side of the Qinghai-Xizang Plateau to the precipitation of SJY increased during the negative anomaly of precipitation in SJY， while the contribution rate of other water vapor sources decreased.

Keywords

• sanjiangyuan
• water vapor transport
• abnormal precipitation
• flexpart