The Characteristics of Water Vapor Transport Based on Lagrangian Method in the Zoige， Qinghai-Xizang Plateau

Abstract

The drought index has always been a practical standard for assessing a specific region's dry and wet state.In order to better understand the spatial distribution pattern of water vapor transport in the Zoige region of the Qinghai-Xizang Plateau under extreme dry and wet conditions， this paper calculates the monthly standardized precipitation evapotranspiration index based on the ground observation data.It extracts the extreme drought and wet conditions in the Zoige region of the Qinghai-Xizang Plateau from 2000 to 2017.The Lagrangian backward trajectory model is used to simulate the water vapor transport path under extreme dry and wet conditions and evaluate the location of potential evapotranspiration water vapor sources and their contributions to the water vapor transport in the study area.The results show that the main water vapor transport path is concentrated in the south branch transport path affected by the southwest monsoon during the wet period.The route originates from the Arabian Sea and the Bay of Bengal and finally arrives at the Zoige from the western and southern flank of the Qinghai-Xizang Plateau.Moreover， the water vapor transport pathway during the drought period is mainly affected by the westerlies.The dominant path starts from North America and the North Atlantic， spreads from west to east， the mid-latitude Eurasian continent， and finally reaches the north of the Qinghai-Xizang Plateau.The main water vapor sources appeared in the Qinghai-Xizang Plateau， Sichuan Basin， Bay of Bengal， Arabian Sea， and other regions.Affected by the water vapor transmission path in different periods， these water vapor sources show different characteristics.In the wet period， the water vapor source is mainly distributed around the south of the Qinghai-Xizang Plateau （the contribution rate is 35.98%）.In contrast， the primary water vapor source during the drought period appears in the northern Qinghai-Xizang Plateau （the contribution rate is 28.35%）.In addition， the contribution rate of water vapor sources from the Arabian Sea and the Bay of Bengal is higher in the wet period.In contrast， the contribution rate of water vapor in the local Zoige area and Sichuan is higher in the drought period.The analysis results will help to understand the formation mechanism of water vapor during extreme drought and wet states， how the water vapor sources work， and the contribution rate of the water vapor sources.This research can deepen the understanding of the mechanism of drought and flood disasters.

Keywords

• standardized precipitation evapotranspiration index
• water vapor transport
• wet and drought evolution
• lagrangian backward trajectory model
• drought event